MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Origins of Life and Evolution of the Biosphere' source. Thu, 09 Feb 2012 16:56:53 +0100 http://www.medworm.com/index.php?rid=5546089&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22200905%26dopt%3DAbstract Authors: Fournier GP, Andam CP, Alm EJ, Gogarten JP Abstract Aminoacyl-tRNA synthetases (aaRS) consist of several families of functionally conserved proteins essential for translation and protein synthesis. Like nearly all components of the translation machinery, most aaRS families are universally distributed across cellular life, being inherited from the time of the Last Universal Common Ancestor (LUCA). However, unlike the rest of the translation machinery, aaRS have undergone numerous ancient horizontal gene transfers, with several independent events detected between domains, and some possibly involving lineages diverging before the time of LUCA. These transfers reveal the complexity of molecular evolution at this early time, and the chimeric nature of genomes within cells that ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5546089 Tue, 27 Dec 2011 05:00:00 +0100 5546089 http://www.medworm.com/index.php?rid=5510473&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139510%26dopt%3DAbstract Authors: Costanzo G, Pino S, Botta G, Saladino R, Di Mauro E Abstract Nucleic bases are obtained by heating formamide in the presence of various catalysts. Formamide chemistry also allows the formation of acyclonucleosides and the phosphorylation of nucleosides in every possible position, also affording 2',3' and 3',5' cyclic forms. We have reported that 3',5' cyclic GMP and 3',5' cyclic AMP polymerize in abiotic conditions yielding short oligonucleotides. The characterization of this reaction is being pursued, several of its parameters have been determined and experimental caveats are reported. The yield of non-enzymatic polymerization of cyclic purine nucleotides is very low. Polymerization is strongly enhanced by the presence of base-complementary RNA sequences. PMID: 221395... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5510473 Sat, 03 Dec 2011 05:00:00 +0100 5510473 http://www.medworm.com/index.php?rid=5510472&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139511%26dopt%3DAbstract Authors: Kua J, Bada JL Abstract We examine the stability of three key components needed to establish an RNA World under a range of potential conditions present on the early earth. The stability of ribose, cytosine, and the phosphodiester bond are estimated at different pH values and temperatures by extrapolating available experimental data. The conditions we have chosen range from highly acidic or alkaline hydrothermal vents, to the milder conditions in a primordial ocean at a range of atmospheric CO(2) partial pressures. PMID: 22139511 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5510472 Sat, 03 Dec 2011 05:00:00 +0100 5510472 http://www.medworm.com/index.php?rid=5510471&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139512%26dopt%3DAbstract Authors: Simoncini E, Russell MJ, Kleidon A Abstract Off-axis Hydrothermal Systems (HSs) are seen as the possible setting for the emergence of life. As the availability of free energy is a general requirement to drive any form of metabolism, we ask here under which conditions free energy generation by geologic processes is greatest and relate these to the conditions found at off-axis HSs. To do so, we present a conceptual model in which we explicitly capture the energetics of fluid motion and its interaction with exothermic reactions to maintain a state of chemical disequilibrium. Central to the interaction is the temperature at which the exothermic reactions take place. This temperature not only sets the equilibrium constant of the chemical reactions and thereby the distance of th... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5510471 Sat, 03 Dec 2011 05:00:00 +0100 5510471 http://www.medworm.com/index.php?rid=5510470&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139513%26dopt%3DAbstract Authors: Heller R, Barnes R, Leconte J Abstract Stellar radiation has conservatively been used as the key constraint to planetary habitability. We review here the effects of tides, exerted by the host star on the planet, on the evolution of the planetary spin. Tides initially drive the rotation period and the orientation of the rotation axis into an equilibrium state but do not necessarily lead to synchronous rotation. As tides also circularize the orbit, eventually the rotation period does equal the orbital period and one hemisphere will be permanently irradiated by the star. Furthermore, the rotational axis will become perpendicular to the orbit, i.e. the planetary surface will not experience seasonal variations of the insolation. We illustrate here how tides alter the spins of p... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5510470 Sat, 03 Dec 2011 05:00:00 +0100 5510470 http://www.medworm.com/index.php?rid=5510469&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139514%26dopt%3DAbstract Authors: Parker ET, Cleaves HJ, Callahan MP, Dworkin JP, Glavin DP, Lazcano A, Bada JL Abstract Stanley Miller's 1958 H(2)S-containing experiment, which included a simulated prebiotic atmosphere of methane (CH(4)), ammonia (NH(3)), carbon dioxide (CO(2)), and hydrogen sulfide (H(2)S) produced several alkyl amino acids, including the α-, β-, and γ-isomers of aminobutyric acid (ABA) in greater relative yields than had previously been reported from his spark discharge experiments. In the presence of H(2)S, aspartic and glutamic acids could yield alkyl amino acids via the formation of thioimide intermediates. Radical chemistry initiated by passing H(2)S through a spark discharge could have also enhanced alkyl amino acid synthesis by generating alkyl radicals that can help form the a... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5510469 Sat, 03 Dec 2011 05:00:00 +0100 5510469 http://www.medworm.com/index.php?rid=5510468&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139515%26dopt%3DAbstract Authors: Kwok S Abstract Stars in the late stages of evolution are able to synthesize complex organic compounds with aromatic and aliphatic structures over very short time scales. These compounds are ejected into the interstellar medium and distributed throughout the Galaxy. The structures of these compounds are similar to the insoluble organic matter found in meteorites. In this paper, we discuss to what extent stellar organics has enriched the primordial Solar System and possibly the early Earth. PMID: 22139515 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5510468 Sat, 03 Dec 2011 05:00:00 +0100 5510468 http://www.medworm.com/index.php?rid=5510467&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139516%26dopt%3DAbstract Authors: Joshi PC, Aldersley MF, Price JD, Zagorevski DV, Ferris JP Abstract The montmorillonite-catalyzed reactions of D, L-ImpA with D, L-ImpU generates RNA-like oligomers. The structures of the dimers to pentamers were investigated and homochiral products were identified in greater amounts than would be expected if theoretical amounts of each were formed. The homochirality increased from 64% to 97% as the chain length increased from dimers to pentamers. Investigation of the effect of pH, occupancy of the interlayer space and the influence of various cations in the reaction provided further insight into physical process in the mechanism of the catalysis. A detailed analysis of dimers was carried out in view of there being key intermediates towards formation of higher oligomers. T... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5510467 Sat, 03 Dec 2011 05:00:00 +0100 5510467 http://www.medworm.com/index.php?rid=5510466&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139517%26dopt%3DAbstract Authors: Schwartzman D, Middendorf G Abstract We propose consideration of at least two possible evolutionary paths for the emergence of intelligent life with the potential for technical civilization. The first is the path via encephalization of homeothermic animals; the second is the path to swarm intelligence of so-called superorganisms, in particular the social insects. The path to each appears to be facilitated by environmental change: homeothermic animals by decreased climatic temperature and for swarm intelligence by increased oxygen levels. PMID: 22139517 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5510466 Sat, 03 Dec 2011 05:00:00 +0100 5510466 http://www.medworm.com/index.php?rid=5510465&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139518%26dopt%3DAbstract We describe here the design and characterization of new peptides that form soluble β-sheet aggregates that serve to significantly accelerate their ligation and self-replication. We then discuss the relevance of these phenomena to early molecular evolution, in light of additional functionality associated with β-sheet assemblies. PMID: 22139518 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5510465 Sat, 03 Dec 2011 05:00:00 +0100 5510465 http://www.medworm.com/index.php?rid=5510463&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139519%26dopt%3DAbstract Authors: Colín-García M, Kanawati B, Harir M, Schmitt-Kopplin P, Amils R, Parro V, García M, Fernández-Remolar D Abstract Biomarkers are molecules that are produced by or can be associated with biological activities. They can be used as tracers that give us an idea of the ancient biological communities that produced them, the paleoenvironmental conditions where they lived, or the mechanism involved in their transformation and preservation. As a consequence, the preservation potential of molecules over time depends largely on their nature, but also on the conditions of the environment, which controls the decomposition kinetics. In this context, proteins and nucleic acids, which are biomolecules bearing biological information, are among the most labile molecules. In this research... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5510463 Sat, 03 Dec 2011 05:00:00 +0100 5510463 http://www.medworm.com/index.php?rid=5510462&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139520%26dopt%3DAbstract Authors: Neubauer D, Vrtala A, Leitner JJ, Firneis MG, Hitzenberger R Abstract A radiative convective model to calculate the width and the location of the life supporting zone (LSZ) for different, alternative solvents (i.e. other than water) is presented. This model can be applied to the atmospheres of the terrestrial planets in the solar system as well as (hypothetical, Earth-like) terrestrial exoplanets. Cloud droplet formation and growth are investigated using a cloud parcel model. Clouds can be incorporated into the radiative transfer calculations. Test runs for Earth, Mars and Titan show a good agreement of model results with observations. PMID: 22139520 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5510462 Sat, 03 Dec 2011 05:00:00 +0100 5510462 http://www.medworm.com/index.php?rid=5510461&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139521%26dopt%3DAbstract Authors: Maccone C Abstract Darwinian evolution theory may be regarded as a part of SETI theory in that the factor f(l) in the Drake equation represents the fraction of planets suitable for life on which life actually arose. In this paper we firstly provide a statistical generalization of the Drake equation where the factor f(l) is shown to follow the lognormal probability distribution. This lognormal distribution is a consequence of the Central Limit Theorem (CLT) of Statistics, stating that the product of a number of independent random variables whose probability densities are unknown and independent of each other approached the lognormal distribution when the number of factors increased to infinity. In addition we show that the exponential growth of the number of species typical... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5510461 Sat, 03 Dec 2011 05:00:00 +0100 5510461 http://www.medworm.com/index.php?rid=5473683&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22127782%26dopt%3DAbstract Authors: Schwartz AW PMID: 22127782 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5473683 Wed, 30 Nov 2011 05:00:00 +0100 5473683 http://www.medworm.com/index.php?rid=5378216&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22048894%26dopt%3DAbstract Authors: Cairns-Smith AG PMID: 22048894 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5378216 Thu, 03 Nov 2011 04:00:00 +0100 5378216 http://www.medworm.com/index.php?rid=5343621&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22011879%26dopt%3DAbstract Authors: Baú JP, Carneiro CE, de Souza Junior IG, de Souza CM, da Costa AC, di Mauro E, Zaia CT, Coronas J, Casado C, de Santana H, Zaia DA Abstract The interactions of adenine and thymine with and adsorption on zeolites were studied using different techniques. There were two main findings. First, as shown by X-ray diffractometry, thymine increased the decomposition of the zeolites (Y, ZSM-5) while adenine prevented it. Second, zeolite Y adsorbed almost the same amount of adenine and thymine, thus both nucleic acid bases could be protected from hydrolysis and UV radiation and could be available for molecular evolution. The X-ray diffractometry and SEM showed that artificial seawater almost dissolved zeolite A. The adsorption of adenine on ZSM-5 zeolite was higher than that of thym... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5343621 Thu, 20 Oct 2011 04:00:00 +0100 5343621 http://www.medworm.com/index.php?rid=5226909&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21915622%26dopt%3DAbstract Authors: Schwartz AW PMID: 21915622 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=5226909 Wed, 14 Sep 2011 04:00:00 +0100 5226909 http://www.medworm.com/index.php?rid=4999043&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21728078%26dopt%3DAbstract This article reports rate constants for thiol-thioester exchange (k (ex)), and for acid-mediated (k (a)), base-mediated (k (b)), and pH-independent (k (w)) hydrolysis of S-methyl thioacetate and S-phenyl 5-dimethylamino-5-oxo-thiopentanoate-model alkyl and aryl thioalkanoates, respectively-in water. Reactions such as thiol-thioester exchange or aminolysis could have generated molecular complexity on early Earth, but for thioesters to have played important roles in the origin of life, constructive reactions would have needed to compete effectively with hydrolysis under prebiotic conditions. Knowledge of the kinetics of competition between exchange and hydrolysis is also useful in the optimization of systems where exchange is used in applications such as self-assembly or reversible binding. ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4999043 Mon, 04 Jul 2011 23:00:00 +0100 4999043 http://www.medworm.com/index.php?rid=4999044&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21717172%26dopt%3DAbstract Authors: Carneiro CE, Berndt G, de Souza Junior IG, de Souza CM, Paesano A, da Costa AC, di Mauro E, de Santana H, Zaia CT, Zaia DA In the present work the interactions of nucleic acid bases with and adsorption on clays were studied at two pHs (2.00, 7.00) using different techniques. As shown by Mössbauer and EPR spectroscopies and X-ray diffractometry, the most important finding of this work is that nucleic acid bases penetrate into the interlayer of the clays and oxidize Fe(2+) to Fe(3+), thus, this interaction cannot be regarded as a simple physical adsorption. For the two pHs the order of the adsorption of nucleic acid bases on the clays was: adenine ≈ cytosine > thymine > uracil. The adsorption of adenine and cytosine on clays increased with decreasing of the ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4999044 Wed, 29 Jun 2011 23:00:00 +0100 4999044 http://www.medworm.com/index.php?rid=4903960&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21626404%26dopt%3DAbstract Authors: Bhushan B, Shanker U, Kamaluddin Manganese exists in different oxidation states under different environmental conditions with respect to redox potential. Various forms of manganese oxides, namely, Manganosite (MnO), Bixbyite (Mn(2)O(3)), Hausmannite (Mn(3)O(4)) and Pyrolusite (MnO(2)) were synthesized and their possible role in chemical evolution studied. Adsorption studies of ribose nucleotides (5'-AMP, 5'-GMP, 5'-CMP and 5'-UMP) on these manganese oxides at neutral pH, revealed a higher binding affinity to manganosite (MnO) compared to the other manganese oxides. That manganese oxides having a lower Mn-O ratio show higher binding affinity for the ribonucleotides indirectly implies that such oxides may have provided a surface onto which biomonomers could have been concentrat... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4903960 Mon, 30 May 2011 23:00:00 +0100 4903960 http://www.medworm.com/index.php?rid=4903961&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21626182%26dopt%3DAbstract Authors: Schwartz AW PMID: 21626182 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4903961 Fri, 27 May 2011 23:00:00 +0100 4903961 http://www.medworm.com/index.php?rid=4853877&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21562847%26dopt%3DAbstract Authors: Plasson R, Tsuji M, Kamata M, Asakura K A good comprehension of the reactivity of peptides in aqueous solution is fundamental in prebiotic chemistry, namely for understanding their stability and behavior in primitive oceans. Relying on the stereoselectivity of the involved reactions, there is a huge interest in amino acid derivatives for explaining the spontaneous emergence of homochirality on primitive Earth. The corresponding kinetic and thermodynamic parameters are however still poorly known in the literature. We studied the reactivity of alanylalanine in acidic to neutral conditions as a model system. The hydrolysis into amino acids, the epimerization of the N-terminal residue, and the cyclization into diketopiperazine could be successfully identified and studied. This kin... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4853877 Wed, 11 May 2011 23:00:00 +0100 4853877 http://www.medworm.com/index.php?rid=4748323&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21484535%26dopt%3DAbstract Authors: Saladino R, Crestini C, Cossetti C, Di Mauro E, Deamer D Mineral components of the Murchison meteorite were investigated in terms of potential catalytic effects on synthetic and hydrolytic reactions related to ribonucleic acid. We found that the mineral surfaces catalyzed condensation reactions of formamide to form carboxylic acids, amino acids, nucleobases and sugar precursors. These results suggest that formamide condensation reactions in the parent bodies of carbonaceous meteorites could give rise to multiple organic compounds thought to be required for the emergence of life. Previous studies have demonstrated similar catalytic effects for mineral assemblies likely to have been present in the early Earth environment. The minerals had little or no effect in promoting hydroly... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4748323 Mon, 11 Apr 2011 23:00:00 +0100 4748323 http://www.medworm.com/index.php?rid=4748363&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21461647%26dopt%3DAbstract Authors: Izumi Y, Nakagawa K One of the leading hypotheses regarding the origin of prebiotic molecules on primitive Earth is that they formed from inorganic molecules in extraterrestrial environments and were delivered by meteorites, space dust and comets. To evaluate the availability of extraterrestrial amino acids, it is necessary to examine their decomposition and oligomerization rates as induced by extraterrestrial energy sources, such as vacuum ultraviolet (VUV) and X-ray photons and high energy particles. This paper reports the quantum yields of decomposition ((8.2 ± 0.7) × 10(-2) photon(-1)) and homo-dimerization ((1.2 ± 0.3) × 10(-3) photon(-1)) and decomposition of the dimer (0.24 ± 0.06 photon(-1)) of solid L: -alanine (Ala) induced by VUV light with ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4748363 Fri, 01 Apr 2011 23:00:00 +0100 4748363 http://www.medworm.com/index.php?rid=4748340&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21461648%26dopt%3DAbstract Authors: Holm NG, Baltscheffsky H The discovery that photosynthetic bacterial membrane-bound inorganic pyrophosphatase (PPase) catalyzed light-induced phosphorylation of orthophosphate (Pi) to pyrophosphate (PPi) and the capability of PPi to drive energy requiring dark reactions supported PPi as a possible early alternative to ATP. Like the proton-pumping ATPase, the corresponding membrane-bound PPase also is a H(+)-pump, and like the Na(+)-pumping ATPase, it can be a Na(+)-pump, both in archaeal and bacterial membranes. We suggest that PPi and Na(+) transport preceded ATP and H(+) transport in association with geochemistry of the Earth at the time of the origin and early evolution of life. Life may have started in connection with early plate tectonic processes coupled to alkaline hydr... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4748340 Fri, 01 Apr 2011 23:00:00 +0100 4748340 http://www.medworm.com/index.php?rid=4637634&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21431891%26dopt%3DAbstract Authors: Rivas M, Becerra A, Peretó J, Bada JL, Lazcano A We critically examine the proposal by Wächtershäuser (Prokaryotes 1:275-283, 2006a, Philos Trans R Soc Lond B Biol Sci 361: 787-1808, 2006b) that putative transition metal binding sites in protein components of the translation machinery of hyperthermophiles provide evidence of a direct relationship with the FeS clusters of pyrite and thus indicate an autotrophic origin of life in volcanic environments. Analysis of completely sequenced cellular genomes of Bacteria, Archaea and Eucarya does not support the suggestion by Wächtershäuser (Prokaryotes 1:275-283, 2006a, Philos Trans R Soc Lond B Biol Sci 361: 787-1808, 2006b) that aminoacyl-tRNA synthetases and ribosomal proteins bear sequence signatures typical of strong covalent... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4637634 Thu, 24 Mar 2011 00:00:00 +0100 4637634 http://www.medworm.com/index.php?rid=4637639&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21424401%26dopt%3DAbstract Authors: Saladino R, Barontini M, Cossetti C, Di Mauro E, Crestini C The thermal condensation of formamide in the presence of mineral borates is reported. The products afforded are precursors of nucleic acids, amino acids derivatives and carboxylic acids. The efficiency and the selectivity of the reaction was studied in relation to the elemental composition of the 18 minerals analyzed. The possibility of synthesizing at the same time building blocks of both genetic and metabolic apparatuses, along with the production of amino acids, highlights the interest of the formamide/borate system in prebiotic chemistry. PMID: 21424401 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4637639 Sat, 19 Mar 2011 00:00:00 +0100 4637639 http://www.medworm.com/index.php?rid=4522819&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21318405%26dopt%3DAbstract Authors: Brack A, Schwartz A PMID: 21318405 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4522819 Sat, 12 Feb 2011 00:00:00 +0100 4522819 http://www.medworm.com/index.php?rid=4397949&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21221809%26dopt%3DAbstract Authors: Grew ES, Bada JL, Hazen RM The RNA World is generally thought to have been an important link between purely prebiotic (>3.7 Ga) chemistry and modern DNA/protein biochemistry. One concern about the RNA World hypothesis is the geochemical stability of ribose, the sugar moiety of RNA. Prebiotic stabilization of ribose by solutions associated with borate minerals, notably colemanite, ulexite, and kernite, has been proposed as one resolution to this difficulty. However, a critical unresolved issue is whether borate minerals existed in sufficient quantities on the primitive Earth, especially in the period when prebiotic synthesis processes leading to RNA took place. Although the oldest reported colemanite and ulexite are 330 Ma, and the oldest reported kernite, 19 Ma, boron is... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4397949 Sat, 08 Jan 2011 00:00:00 +0100 4397949 http://www.medworm.com/index.php?rid=4273649&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21161385%26dopt%3DAbstract Authors: Ruiz-Bermejo M, Rivas LA, Palacín A, Menor-Salván C, Osuna-Esteban S Clasically, prebiotic chemistry has focused on the production and identification of simple organic molecules, many of them forming part of "intractable polymers" named tholins. In a previous work, we demonstrated that in experiments using an external energy source and inorganic carbon the aqueous aerosols improved the formation of hydrophilic tholins. Herein, we elucidate the role of pH (from 4 to 12) in prebiotic experiments using saline aqueous aerosols, spark discharges and an atmosphere containing CH(4). At all values of pH, the saline aqueous aerosols increased the production of a significant variety of carboxylic acids that could have been present in a primitive Krebs cycle. Moreover, the study for th... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4273649 Thu, 16 Dec 2010 00:00:00 +0100 4273649 http://www.medworm.com/index.php?rid=4273647&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21161387%26dopt%3DAbstract Authors: Faglioni F, Cuesta IG The parity-violation energy difference between enantiomeric forms of the same amino acid sequence, from the amyloid β-peptide involved in Alzheimer's desease, in both α-helix and β-sheet configurations, is investigated with ab-initio techniques. To this end, we develop an extension of the N2 computational scheme that selectively includes neighboring amino acids to preserve the relevant H-bonds. In agreement with previous speculations, it is found that the helical α structure is associated with larger parity-violation energy differences than the corresponding β form. Implications for the evolution of biological homochirality are discussed as well as the relative importance of various effects in determining the parity-violation energy. PMID: 211613... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4273647 Thu, 16 Dec 2010 00:00:00 +0100 4273647 http://www.medworm.com/index.php?rid=4273648&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21161386%26dopt%3DAbstract Authors: Schwartz AW PMID: 21161386 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4273648 Wed, 15 Dec 2010 00:00:00 +0100 4273648 http://www.medworm.com/index.php?rid=4249430&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21127982%26dopt%3DAbstract Authors: Hammarström P, Ali MM, Mishra R, Salagic B, Svensson S, Tengvall P, Lundström I Amyloid fibrils are composed of self assembled stacked peptide or protein molecules folded and trapped in a stable cross-beta-sheet conformation. The amyloid fibrillation mechanism represents an intriguing self-catalyzed process rendering replication of a molecular conformational memory of interest for prebiotic chemistry. Herein we describe how a solid surface can be rendered auto-catalytic for fibrillation of a protein solution. We have discovered that a hydrophobic silicon or glass surface can be made to continuously fibrillate solutions of insulin monomers under stressed conditions (pH 1.6, 65°C). It was found that the surface acts as a platform for the formation of nascent seeds that induce... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4249430 Fri, 03 Dec 2010 00:00:00 +0100 4249430 http://www.medworm.com/index.php?rid=4184058&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21080073%26dopt%3DAbstract Authors: Balleza D Mechanosensitive (MS) channels can prevent bacterial bursting during hypo-osmotic shocks by responding to increases in lateral tension at the membrane level through an integrated and coordinated opening mechanism. Mechanical regulation in protocells could have been one of the first mechanisms to evolve in order to preserve their integrity against changing environmental conditions. How has the rich functional diversity found in present cells been created throughout evolution, and what did the primordial MS channels look like? This review has been written with the aim of identifying which factors may have been important for the appearance of the first osmotic valve in a prebiotic context, and what this valve may have been like. It highlights the mechanical properties o... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4184058 Wed, 17 Nov 2010 00:00:00 +0100 4184058 http://www.medworm.com/index.php?rid=4165274&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21063908%26dopt%3DAbstract Authors: Parker ET, Cleaves HJ, Callahan MP, Dworkin JP, Glavin DP, Lazcano A, Bada JL Original extracts from an unpublished 1958 experiment conducted by the late Stanley L. Miller were recently found and analyzed using modern state-of-the-art analytical methods. The extracts were produced by the action of an electric discharge on a mixture of methane (CH(4)), hydrogen sulfide (H(2)S), ammonia (NH(3)), and carbon dioxide (CO(2)). Racemic methionine was formed in significant yields, together with other sulfur-bearing organic compounds. The formation of methionine and other compounds from a model prebiotic atmosphere that contained H(2)S suggests that this type of synthesis is robust under reducing conditions, which may have existed either in the global primitive atmosphere or in localiz... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4165274 Wed, 10 Nov 2010 00:00:00 +0100 4165274 http://www.medworm.com/index.php?rid=4151349&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21057875%26dopt%3DAbstract Authors: Rosen G Recent observations and theoretical studies have shown that non-baryonic Cold Dark Matter (CDM), which constitutes about 84% of all matter in the Universe, may feature a complex-scalar-field that carries particles of mass [Formula: see text] with the associated Compton range [Formula: see text] a distance on the scale of extended bionucleic acids and living cells. Such a complex-scalar-field can enter a weak-isospin Lorentz-invariant interaction that generates the flow of right-handed electrons and induces a chirality-imbued quantum chemistry on the m (-1) scale. A phenomenological Volterra-type equation is proposed for the CDM-impacted time development of N, the number of base pairs in the most advanced organism at Earth-age t. The solution to this equation suggests t... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4151349 Sat, 06 Nov 2010 00:00:00 +0100 4151349 http://www.medworm.com/index.php?rid=4151348&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21057876%26dopt%3DAbstract Authors: Guimarães RC An investigation of the biosynthesis pathways producing glycine and serine was necessary to clarify an apparent inconsistency between the self-referential model (SRM) for the formation of the genetic code and the model of coevolution of encodings and of amino acid biosynthesis routes. According to the SRM proposal, glycine was the first amino acid encoded, followed by serine. The coevolution model does not state precisely which the first encodings were, only presenting a list of about ten early assignments including the derivation of glycine from serine-this being derived from the glycolysis intermediate glycerate, which reverses the order proposed by the self-referential model. Our search identified the glycine-serine pathway of syntheses based on one-carbon sou... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=4151348 Sat, 06 Nov 2010 00:00:00 +0100 4151348 http://www.medworm.com/index.php?rid=3933979&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20814743%26dopt%3DAbstract Authors: Najafpour MM In this paper a few calcium-manganese oxides and calcium-manganese minerals are studied as catalysts for water oxidation. The natural mineral marokite is also studied as a catalyst for water oxidation for the first time. Marokite is made up of edge-sharing Mn(3+) in a distorted octahedral environment and eight-coordinate Ca(2+) centered polyhedral layers. The structure is similar to recent models of the oxygen evolving complex in photosystem II. Thus, the oxygen evolving complex in photosystem II does not have an unusual structure and could be synthesized hydrothermally. Also in this paper, oxygen evolution is studied with marokite (CaMn(2)O(4)), pyrolusite (MnO(2)) and compared with hollandite (Ba(0.2)Ca(0.15)K(0.3)Mn(6.9)Al(0.2)Si(0.3)O(16)), hausmannite (Mn(3)O... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3933979 Fri, 03 Sep 2010 23:00:00 +0100 3933979 http://www.medworm.com/index.php?rid=3933980&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20811777%26dopt%3DAbstract Authors: Fishkis M The paper presents a model of coevolution of short peptides (P) and short oligonucleotides (N) at an early stage of chemical evolution leading to the origin of life. The model describes polymerization of both P and N types of molecules on mineral surfaces in aqueous solution at moderate temperatures. It is assumed that amino acid and nucleotide monomers were available in a prebiotic milieu, that periodic variation in environmental conditions between dry/warm and wet/cool took place and that energy sources were available for the polymerization. An artificial chemistry approach in combination with agent-based modeling was used to explore chemical evolution from an initially random mixture of monomers. It was assumed that the oligonucleotides could serve as templates fo... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3933980 Tue, 31 Aug 2010 23:00:00 +0100 3933980 http://www.medworm.com/index.php?rid=3890762&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20725859%26dopt%3DAbstract Authors: Joshi PC, Aldersley MF, Ferris JP Selective adsorption of D, L-ImpA with D, L-ImpU on the platelets of montmorillonite demonstrates an important reaction pathway for the origin of homochirality in RNA synthesis. Our earlier studies have shown that the individual reactions of D, L-ImpA or D, L-ImpU on montmorillonite catalyst produced oligomers which were only partially inhibited by the incorporation of both D- and L-enantiomers. Homochirality in these reactions was largely due to the formation of cyclic dimers that cannot elongate. We investigated the quaternary reactions of D, L-ImpA with D, L-ImpU on montmorillonite. The chain length of these oligomers increased from 9-mer to 11-mer as observed by HPLC, with a concominant increase in the yield of linear dimers and higher oli... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3890762 Thu, 19 Aug 2010 23:00:00 +0100 3890762 http://www.medworm.com/index.php?rid=3855007&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20697814%26dopt%3DAbstract Authors: Alpermann T, Rüdel K, Rüger R, Steiniger F, Nietzsche S, Filiz V, Förster S, Fahr A, Weigand W According to Wächtershäuser's "Iron-Sulfur-World" one major requirement for the development of life on the prebiotic Earth is compartmentalization. Vesicles spontaneously formed from amphiphilic components containing a specific set of molecules including sulfide minerals may have lead to the first autotrophic prebiotic units. The iron sulfide minerals may have been formed by geological conversions in the environment of deep-sea volcanos (black smokers), which can be observed even today. Wächtershäuser postulated the evolution of chemical pathways as fundamentals of the origin of life on earth. In contrast to the classical Miller-Urey experiment, depending on exte... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3855007 Mon, 09 Aug 2010 23:00:00 +0100 3855007 http://www.medworm.com/index.php?rid=3824066&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20683773%26dopt%3DAbstract Authors: Wattis JA We review the existing mathematical models which describe physicochemical mechanisms capable of producing a symmetry-breaking transition to a state in which one chirality dominates the other. A new model is proposed, with the aim of elucidating the fundamental processes at work in the crystal grinding systems of Viedma (Phys Rev Lett 94:065504, 2005) and Noorduin (J Am Chem Soc 130:1158-1159, 2008). We simplify the model as far as possible to uncover the fundamental competitive process which causes the symmetry-breaking, and analyse other simplifications which might be expected to show symmetry-breaking. PMID: 20683773 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3824066 Tue, 03 Aug 2010 23:00:00 +0100 3824066 http://www.medworm.com/index.php?rid=3719494&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20585856%26dopt%3DAbstract Authors: Carny O, Gazit E Any attempt to uncover the origins of life must tackle the known 'blind watchmaker problem'. That is to demonstrate the likelihood of the emergence of a prebiotic system simple enough to be formed spontaneously and yet complex enough to allow natural selection that will lead to Darwinistic evolution. Studies of short aromatic peptides revealed their ability to self-assemble into ordered and stable structures. The unique physical and chemical characteristics of these peptide assemblies point out to their possible role in the origins of life. We have explored mechanisms by which self-assembling short peptides and RNA fragments could interact together and go through a molecular co-evolution, using diphenylalanine supramolecular assemblies as a model system. The s... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3719494 Mon, 28 Jun 2010 23:00:00 +0100 3719494 http://www.medworm.com/index.php?rid=3691573&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20571915%26dopt%3DAbstract Authors: PMID: 20571915 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3691573 Tue, 22 Jun 2010 23:00:00 +0100 3691573 http://www.medworm.com/index.php?rid=3691574&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20563646%26dopt%3DAbstract Authors: Rand D, Belenky M, Herzfeld J Reactions of short sugars under mild, plausibly prebiotic conditions yield organic microspherules that may have played a role in prebiotic chemistry as primitive reaction vessels. It has been widely thought that nitrogen chemistry, in particular Amadori rearrangement, is central to this process, Here we show that microspherules form in the absence of any nitrogen compounds if the pH is sufficiently low. In particular, while the microspherule formation induced by ammonium acetate (pH 7) is not reproduced by ammonium chloride (pH 5), it is reproduced by oxalic acid and by hydrochloric acid (pH 1). The formation of microspherules in the presence of oxalic acid is similar to that in the presence of ammonium acetate: aqueous reactions of D-erythrose, D... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3691574 Fri, 18 Jun 2010 23:00:00 +0100 3691574 http://www.medworm.com/index.php?rid=3680473&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20559733%26dopt%3DAbstract Authors: Kundell FA A suggested pioneer organism for the Wächtershäuser origin of life hypothesis is presented. In this scenario, a cubic pyrite crystal edge serves as a catalytic surface for the production of a proto-nucleic acid. Computational analysis demonstrates how the vacant cubic pyrite edge could be populated by iron(II) and hydrogen phosphate, capped with a distorted iron pentacarbonyl. A bridging iron sulfide then forms blocking one side of the edge. The carbonyl on the other side of the edge can then react with either existing uracil or cytosine, to produce a nitrogen-iron carbonyl intermediate. This intermediate serves as a free radical initiator for a polymerization of carbon monoxide and molecular hydrogen. After the fourth carbon is added to the chain, the polymer... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3680473 Thu, 17 Jun 2010 23:00:00 +0100 3680473 http://www.medworm.com/index.php?rid=3599755&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20499186%26dopt%3DAbstract Authors: Badescu V Free-floating planets (FFPs) might originate either around a star or in solitary fashion. These bodies can retain molecular gases atmospheres which, upon cooling, have basal pressures of tens of bars or more. Pressure-induced opacity of these gases prevents such a body from eliminating its internal radioactive heat and its surface temperature can exceed for a long term the melting temperature of a life-supporting solvent. In this paper two non-aqueous but still polar solvents are considered: hydrogen sulfide and ammonia. Thermodynamic requirements to be fulfilled by a hypothetic gas constituent of a life-supporting FFP's atmosphere are studied. The three gases analyzed here (nitrogen, methane and ethane) are candidates. We show that bodies with ammonia oceans are pos... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3599755 Mon, 24 May 2010 23:00:00 +0100 3599755 http://www.medworm.com/index.php?rid=3538991&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20443139%26dopt%3DAbstract The Emergence and Evolution of Life in a "Fatty Acid World" Based on Quantum Mechanics. Orig Life Evol Biosph. 2010 May 5; Authors: Tamulis A, Grigalavicius M Quantum mechanical based electron correlation interactions among molecules are the source of the weak hydrogen and Van der Waals bonds that are critical to the self-assembly of artificial fatty acid micelles. Life on Earth or elsewhere could have emerged in the form of self-reproducing photoactive fatty acid micelles, which gradually evolved into nucleotide-containing micelles due to the enhanced ability of nucleotide-coupled sensitizer molecules to absorb visible light. Comparison of the calculated absorption spectra of micelles with and without nucleotides confirmed this idea and supports the idea of the emergence and e... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3538991 Tue, 04 May 2010 23:00:00 +0100 3538991 http://www.medworm.com/index.php?rid=3515222&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20422292%26dopt%3DAbstract Authors: Weber BH PMID: 20422292 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3515222 Mon, 26 Apr 2010 23:00:00 +0100 3515222 http://www.medworm.com/index.php?rid=3499568&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20407927%26dopt%3DAbstract Authors: Fry I It is commonly accepted among origin-of-life scientists that the emergence of life was an evolutionary process involving at one stage or other the working of natural selection. Researchers disagree, however, on the nature of the chemical infrastructure that could have formed prebiotically, enabling the evolutionary process. The division of the origin-of-life research community into 'geneticists' and 'metabolists' usually revolves around the issue whether the first to arise prebiotically was a genetic polymer or a primitive metabolic system. In this paper I offer an alternative classification based on the attitude to the onset of natural selection. From this perspective I add to the conventional division between gene-first and metabolism-first groups a position I call "pr... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3499568 Tue, 20 Apr 2010 23:00:00 +0100 3499568 http://www.medworm.com/index.php?rid=3499567&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20407928%26dopt%3DAbstract Authors: Haydon N, McGlynn SE, Robus O The origin of life necessitated the formation of catalytic functionalities in order to realize a number of those capable of supporting reactions that led to the proliferation of biologically accessible molecules and the formation of a proto-metabolic network. Here, the discussion of the significance of quantum behavior on biological systems is extended from recent hypotheses exploring brain function and DNA mutation to include origins of life considerations in light of the concept of quantum decoherence and the transition from the quantum to the classical. Current understandings of quantum systems indicate that in the context of catalysis, substrate-catalyst interaction may be considered as a quantum measurement problem. Exploration of catalytic f... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3499567 Tue, 20 Apr 2010 23:00:00 +0100 3499567 http://www.medworm.com/index.php?rid=3408875&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20333546%26dopt%3DAbstract Authors: Boiteau L, Pascal R The emergence and early developments of life are considered from the point of view that contingent events that inevitably marked evolution were accompanied by deterministic driving forces governing the selection between different alternatives. Accordingly, potential energy sources are considered for their propensity to induce self-organization within the scope of the chemical approach to the origin of life. Requirements in terms of quality of energy locate thermal or photochemical activation in the atmosphere as highly likely processes for the formation of activated low-molecular weight organic compounds prone to induce biomolecular self-organization through their ability to deliver quanta of energy matching the needs of early biochemical pathways or the re... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3408875 Wed, 24 Mar 2010 00:00:00 +0100 3408875 http://www.medworm.com/index.php?rid=3354858&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20213158%26dopt%3DAbstract Authors: Weber AL Reaction of 3-5 carbon sugars, glycolaldehyde, and alpha-ketoaldehydes with nitrite under mild anaerobic aqueous conditions yielded ammonia, an essential substrate for the synthesis of nitrogen-containing molecules during abiogenesis. Under the same conditions, ammonia synthesis was not driven by formaldehyde, glyoxylate, 2-deoxyribose, and glucose, a result indicating that the reduction process requires an organic reductant containing either an accessible alpha-hydroxycarbonyl group or an alpha-dicarbonyl group. Small amounts of aqueous Fe(+3) catalyzed the sugar-driven synthesis of ammonia. The glyceraldehyde concentration dependence of ammonia synthesis, and control studies of ammonia's reaction with glyceraldehyde, indicated that ammonia formation is accompanied b... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3354858 Sun, 07 Mar 2010 00:00:00 +0100 3354858 http://www.medworm.com/index.php?rid=3354857&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20213159%26dopt%3DAbstract Authors: Mathew DC, Luthey-Schulten Z We investigate a proposed origins of life scenario involving the clay montmorillonite and its catalytic role in forming oligonucleotides from activated mononucleotides. Clay and mineral surfaces are important for concentrating the reactants and for promoting nucleotide polymerization reactions. Using classical molecular dynamics methods we provide atomic details of reactant conformations prior to polynucleotide formation, lending insight into previously reported experimental observations of this phenomenon. The simulations clarify the catalytic role of metal ions, demonstrate that reactions leading to correct linkages take place primarily in the interlayer, and explain the observed sequence selectivity in the elongation of the chain. The study comp... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3354857 Sun, 07 Mar 2010 00:00:00 +0100 3354857 http://www.medworm.com/index.php?rid=3354856&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20213160%26dopt%3DAbstract We present a wide-field ( approximately 6' x 6') and deep near-infrared (K ( s ) band: 2.14 mum) circular polarization image in the Orion nebula, where massive stars and many low-mass stars are forming. Our results reveal that a high circular polarization region is spatially extended ( approximately 0.4 pc) around the massive star-forming region, the BN/KL nebula. However, other regions, including the linearly polarized Orion bar, show no significant circular polarization. Most of the low-mass young stars do not show detectable extended structure in either linear or circular polarization, in contrast to the BN/KL nebula. If our solar system formed in a massive star-forming region and was irradiated by net circularly polarized radiation, then enantiomeric excesses could have been induced, t... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3354856 Sun, 07 Mar 2010 00:00:00 +0100 3354856 http://www.medworm.com/index.php?rid=3354855&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20213161%26dopt%3DAbstract Authors: Meunier A, Petit S, Cockell CS, El Albani A, Beaufort D During the Hadean to early Archean period (4.5-3.5 Ga), the surface of the Earth's crust was predominantly composed of basalt and komatiite lavas. The conditions imposed by the chemical composition of these rocks favoured the crystallization of Fe-Mg clays rather than that of Al-rich ones (montmorillonite). Fe-Mg clays were formed inside chemical microsystems through sea weathering or hydrothermal alteration, and for the most part, through post-magmatic processes. Indeed, at the end of the cooling stage, Fe-Mg clays precipitated directly from the residual liquid which concentrated in the voids remaining in the crystal framework of the mafic-ultramafic lavas. Nontronite-celadonite and chlorite-saponite covered all the soli... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3354855 Sun, 07 Mar 2010 00:00:00 +0100 3354855 http://www.medworm.com/index.php?rid=3354854&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20213162%26dopt%3DAbstract Authors: Damiano L, Luisi PL In this paper we develop the autopoietic approach to the definition of the living developed by Maturana and Varela in the Seventies. Starting from very simple observations concerning the phenomenology of life, we propose a reformulation of the autopoietic original definition of life which integrates some of the contemporary criticism to it. Our definitional proposal, aiming to stimulate the further development of the autopoietic approach, expresses what remains implicit in the definition of the living originally given by Maturana and Varela: life, as self-production, is a process of cognitive coupling with the environment. PMID: 20213162 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3354854 Sat, 06 Mar 2010 00:00:00 +0100 3354854 http://www.medworm.com/index.php?rid=3340014&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20204517%26dopt%3DAbstract Authors: Bruylants G, Bartik K, Reisse J Many scientists, including one of the authors of the present paper, have devoted time to try to find a definition for life (Bersini and Reisse 2007). It is clear that a consensus will never be reached but, more importantly, it seems that the issue itself could be without major interest. It is indeed impossible to define a "natural" frontier between non-living and living systems and therefore also impossible to define dichotomic criteria which could be used in order to classify systems in one of these two classes (living or non-living). Fuzzy logic provides a natural way to deal with problems where class membership lacks sharply defined criteria. It also offers the possibility to avoid losing time with unnecessary controversies such as deciding w... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3340014 Fri, 05 Mar 2010 00:00:00 +0100 3340014 http://www.medworm.com/index.php?rid=3340013&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20204518%26dopt%3DAbstract Authors: Brack A, Troublé M Life is commonly referred as open systems driven by organic chemistry capable to self reproduce and to evolve. The notion of life has also been extended to non chemical systems such as robots. The key characteristics of living systems, i.e. autonomy, self-replication, self-reproduction, self-organization, self-aggregation, autocatalysis, as defined in chemistry and in robotics, are compared in a dialogue between a chemist and a robotitian. PMID: 20204518 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3340013 Fri, 05 Mar 2010 00:00:00 +0100 3340013 http://www.medworm.com/index.php?rid=3340012&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20204519%26dopt%3DAbstract Authors: Bersini H There is a long tradition of software simulations in theoretical biology to complement pure analytical mathematics which are often limited to reproduce and understand the self-organization phenomena resulting from the non-linear and spatially grounded interactions of the huge number of diverse biological objects. Since John Von Neumann and Alan Turing pioneering works on self-replication and morphogenesis, proponents of artificial life have chosen to resolutely neglecting a lot of materialistic and quantitative information deemed not indispensable and have focused on the rule-based mechanisms making life possible, supposedly neutral with respect to their underlying material embodiment. Minimal life begins at the intersection of a series of processes which need to be ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3340012 Fri, 05 Mar 2010 00:00:00 +0100 3340012 http://www.medworm.com/index.php?rid=3340011&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20204520%26dopt%3DAbstract Authors: Gayon J, Malaterre C, Morange M, Raulin-Cerceau F, Tirard S PMID: 20204520 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3340011 Fri, 05 Mar 2010 00:00:00 +0100 3340011 http://www.medworm.com/index.php?rid=3328112&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20198434%26dopt%3DAbstract Authors: Malaterre C The plurality of definitions of life is often perceived as an unsatisfying situation stemming from still incomplete knowledge about 'what it is to live' as well as from the existence of a variety of methods for reaching a definition. For many, such plurality is to be remedied and the search for a unique and fully satisfactory definition of life pursued. In this contribution on the contrary, it is argued that the existence of such a variety of definitions of life undermines the very feasibility of ever reaching a unique unambiguous definition. It is argued that focusing on the definitions of specific types of 'living systems'-somehow in the same way that one can define specific types of 'flying systems'-could be more fruitful from a heuristic point of view than look... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3328112 Wed, 03 Mar 2010 00:00:00 +0100 3328112 http://www.medworm.com/index.php?rid=3328111&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20198435%26dopt%3DAbstract Authors: Lazcano A If the emergence of life is seen as the evolutionary transition between the non-living and the living, then it may be meaningless to draw a strict line between these two worlds. A comparison between the metabolic- and genetic-first origin-of-life proposals is made. A comparison of the empirical evidence used in favor of the metabolic-first and genetic-first theories of the origin of life shows that many of the observations and experimental findings that are used to argue in favor of one or another view are equally consistent with the premises of both theories and do not unambiguously support neither of them. However, current biology indicates that life could not have evolved in the absence of a genetic replicating mechanism insuring the stability and diversification ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3328111 Wed, 03 Mar 2010 00:00:00 +0100 3328111 http://www.medworm.com/index.php?rid=3328110&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20198436%26dopt%3DAbstract Authors: Forterre P Are viruses alive? Until very recently, answering this question was often negative and viruses were not considered in discussions on the origin and definition of life. This situation is rapidly changing, following several discoveries that have modified our vision of viruses. It has been recognized that viruses have played (and still play) a major innovative role in the evolution of cellular organisms. New definitions of viruses have been proposed and their position in the universal tree of life is actively discussed. Viruses are no more confused with their virions, but can be viewed as complex living entities that transform the infected cell into a novel organism-the virus-producing virions. I suggest here to define life (an historical process) as the mode of existe... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3328110 Wed, 03 Mar 2010 00:00:00 +0100 3328110 http://www.medworm.com/index.php?rid=3328113&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20195774%26dopt%3DAbstract Authors: Morange M The question of life was progressively put aside in the second half of the 20th century with the rise of molecular biology, but has recently re-emerged. Many scientists and philosophers consider that there is no place for this question within biology; that the distinction between living and non-living is arbitrary; and that progress in synthetic biology will finally put this question out of people's minds. I will argue that there is something wrong with the arguments supporting these statements. There are no reasons to exclude the question "What is life?" from biology. But the nature of the question has dramatically changed recently. Instead of being a search for the principles of life, the answer is now sought in the description of the historical process that has co... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3328113 Sat, 27 Feb 2010 00:00:00 +0100 3328113 http://www.medworm.com/index.php?rid=3319715&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20191383%26dopt%3DAbstract Authors: Popa R The criteria used for defining life are influenced by various philosophical visions about life, ranging from holism to reductionism and from mechanistic-reductionism to vitalism. Using different scenarios about the origin and evolution of life as well as properties of energy-dissipative systems, artificial life simulations and basic tenets of xenobiology, guidelines can be established for formulating a definition of life. A definition of life is proposed that is parametric, non-Earth-centric, quantitative and capable of discriminating 'living entities' from 'life'. Living entities are defined as self-maintained systems, capable of adaptive evolution individually, collectively or as a line of descend. Life is a broader concept indicating that the capacity to express thes... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3319715 Sat, 27 Feb 2010 00:00:00 +0100 3319715 http://www.medworm.com/index.php?rid=3316293&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20186488%26dopt%3DAbstract Authors: Raulin Cerceau F Speculations on living beings existing on other planets are found in many written works since the Frenchman Bernard de Fontenelle spoke to the Marquise about the inhabitants of the solar system in his Entretiens sur la pluralité des mondes (1686). It was an entertainment used to teach astronomy more than real considerations about the habitability of our solar system, but it opened the way to some reflections about the possible life forms on other planets. The nineteenth century took up this idea again in a context of planetary studies showing the similarities as well as the differences of the celestial bodies orbiting our Sun. Astronomers attempted to look deeper into the problem of habitability such as Richard Proctor or Camille Flammarion, also well-kno... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3316293 Fri, 26 Feb 2010 00:00:00 +0100 3316293 http://www.medworm.com/index.php?rid=3316292&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20186489%26dopt%3DAbstract Authors: Raulin F How to define life? This very brief paper tries to bring some elements of answer to the question-essential for exobiology-with some chemical considerations. PMID: 20186489 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3316292 Fri, 26 Feb 2010 00:00:00 +0100 3316292 http://www.medworm.com/index.php?rid=3312078&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20182798%26dopt%3DAbstract Authors: Ruiz-Mirazo K, Peretó J, Moreno A In the present, post-genomic times, systemic or holistic approaches to living phenomena are compulsory to overcome the limits of traditional strategies, such as the methodological reductionism of molecular biology. In this paper, we propose that theoretical and philosophical efforts to define life also contribute to those integrative approaches, providing a global theoretical framework that may help to deal with or interpret the huge amount of data being collected by current high-throughput technologies, in this so-called 'omics' revolution. We claim that two fundamental notions can capture the core of the living, (basic) autonomy and open-ended evolution, and that only the complementary combination of these two theoretical constructs off... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3312078 Thu, 25 Feb 2010 00:00:00 +0100 3312078 http://www.medworm.com/index.php?rid=3303059&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20177784%26dopt%3DAbstract Authors: Tirard S Many theories on origin of life at the end of the XIXth century and the beginning of the XXth, generally use conceptions of life instead of explicit definitions of life. This paper presents ideas on the origin of life as studied by Buffon (1707-1788), Lamarck (1744-1829), Darwin (1809-1882), Huxley (1825-1895), Oparin (1894-1980) and Haldane (1892-1964). We show that their conceptions on the evolution of matter and life reveal their conceptions of life rather than their definitions of life. PMID: 20177784 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3303059 Tue, 23 Feb 2010 00:00:00 +0100 3303059 http://www.medworm.com/index.php?rid=3291365&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20169412%26dopt%3DAbstract Authors: Weber BH Erwin Schrödinger defined life not only as a "self-reproducing" aperiodic crystal of DNA coding for proteins but within the context of living entities increasing their order by dissipating matter/energy gradients to maintain themselves away from equilibirium. Since then most definitions of life have focused on the former. But living cells do more than replicate their DNA. Cells also have membrane barriers across which metabolites must move, via which energy transduction as well as information processing occurs, and within which metabolic transformation occurs. An approach of complex systems dynamics, including nonequilibrium thermodynamics, may provide a more robust approach for defining life than a "naked replicator" at the origin of life. The crucial issue beco... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3291365 Fri, 19 Feb 2010 00:00:00 +0100 3291365 http://www.medworm.com/index.php?rid=3284719&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20162362%26dopt%3DAbstract Conclusions. Orig Life Evol Biosph. 2010 Feb 17; Authors: Gayon J The first part of the paper offers philosophical landmarks on the general issue of defining life. section sign1 defends that the recognition of "life" has always been and remains primarily an intuitive process, for the scientist as for the layperson. However we should not expect, then, to be able to draw a definition from this original experience, because our cognitive apparatus has not been primarily designed for this. section sign2 is about definitions in general. Two kinds of definition should be carefully distinguished: lexical definitions (based upon current uses of a word), and stipulative or legislative definitions, which deliberately assign a meaning to a word, for the purpose of clarifying scientific or ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3284719 Wed, 17 Feb 2010 00:00:00 +0100 3284719 http://www.medworm.com/index.php?rid=3172467&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20069373%26dopt%3DAbstract Concentration of Specific Amino Acids at the Catalytic/Active Centers of Highly-Conserved "Housekeeping" Enzymes of Central Metabolism in Archaea, Bacteria and Eukaryota: Is There a Widely Conserved Chemical Signal of Prebiotic Assembly? Orig Life Evol Biosph. 2010 Jan 13; Authors: Pollack JD, Pan X, Pearl DK In alignments of 1969 protein sequences the amino acid glycine and others were found concentrated at most-conserved sites within approximately 15 A of catalytic/active centers (C/AC) of highly conserved kinases, dehydrogenases or lyases of Archaea, Bacteria and Eukaryota. Lysine and glutamic acid were concentrated at least-conserved sites furthest from their C/ACs. Logistic-regression analyses corroborated the "movement" of glycine towards and lysine away from their C/ACs:... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3172467 Wed, 13 Jan 2010 00:00:00 +0100 3172467 http://www.medworm.com/index.php?rid=3015766&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19924561%26dopt%3DAbstract We present an experimental approach to the study of the chirality of three CM2 meteorite solid samples by direct measurement of the optical activity (circular birefringence; CB). The measurements are based on transmission two modulator generalized ellipsometry in conjuction with microscope optics to map the CB of the samples. In spite of the complexity of such optical analysis, these first results indicate the presence of optically active areas in the meteorite solid matrix. In the case of the Murchison sample the statistics of the CB mapping shows a bimodal distribution with a bias to negative CB values. The composition of the active areas probably corresponds to serpentines and other poorly identified phyllosilicate phases. The results are compatible with the hypothesis that in a mineral... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3015766 Fri, 13 Nov 2009 00:00:00 +0100 3015766 http://www.medworm.com/index.php?rid=3000734&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19911298%26dopt%3DAbstract Authors: Illos RA, Clodic G, Bolbach G, Weissbuch I, Lahav M Thioesters of alpha-amino acids are considered as plausible monomers for the generation of the primeval peptides. DL-Leucine-thioethyl esters (LeuSEt), where the L-enantiomer was tagged with deuterium atoms, undergo polycondensation in water or in bicarbonate or imidazole buffer solutions to yield mainly heterochiral (atactic) peptides and diketopiperazine, as analyzed by MALDI-TOF and ESI mass-spectrometry. In variance, when polymerization of DL(d(10))-Leu, first activated with N,N'-carbonyldiimidazole, then initiated with ethanethiol or with DL(d(3))-LeuSEt yielded a library of peptides up to 30 detectable residues where those of homochiral sequence (isotactic) are the dominant diastereoisomers. At these conditions, racemic... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3000734 Fri, 13 Nov 2009 00:00:00 +0100 3000734 http://www.medworm.com/index.php?rid=3000733&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19911299%26dopt%3DAbstract Authors: Ernst KH Symmetry-breaking phenomena in two-dimensional crystallization at surfaces are reviewed and the potential impact to chiral amplification in three-dimensional systems in connection with the origin of homochirality in the biomolecular world is discussed. Adsorption of prochiral molecules leads to two-dimensional conglomerates, i.e., on a local scale spontaneously to homochiral crystal structures. Small enantiomeric excess or chiral impurities in this environment install homochirality on a global scale, that is, on the entire surface. PMID: 19911299 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3000733 Fri, 13 Nov 2009 00:00:00 +0100 3000733 http://www.medworm.com/index.php?rid=3000732&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19911300%26dopt%3DAbstract Authors: Kawasaki T, Nakaoda M, Kaito N, Sasagawa T, Soai K The achiral hydrocarbon tetraphenylethylene crystallizes in enantiomorphous forms (chiral space group: P2(1)) to afford right- and left-handed hemihedral crystals, which can be recognized by solid-state circular dichroism spectroscopic analysis. Chiral organic crystals of tetraphenylethylene mediated enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde to give, in conjunction with asymmetric autocatalysis with amplification of chirality, almost enantiomerically pure (S)- and (R)-5-pyrimidyl alkanols whose absolute configurations were controlled efficiently by the crystalline chirality of the tetraphenylethylene substrate. Tetrakis(p-chlorophenyl)ethylene and tetrakis(p-bromophenyl)ethylene also show chiral... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3000732 Fri, 13 Nov 2009 00:00:00 +0100 3000732 http://www.medworm.com/index.php?rid=3000731&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19911301%26dopt%3DAbstract Authors: Plasson R, Brandenburg A The mechanisms for explaining how a stable asymmetric chemical system can be formed from a symmetric chemical system, in the absence of any asymmetric influence other than statistical fluctuations, have been developed during the last decades, focusing on the non-linear kinetic aspects. Besides the absolute necessity of self-amplification processes, the importance of energetic aspects is often underestimated. Going down to the most fundamental aspects, the distinction between a single object-that can be intrinsically asymmetric-and a collection of objects-whose racemic state is the more stable one-must be emphasized. A system of strongly interacting objects can be described as one single object retaining its individuality and a single asymmetry; weakly ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3000731 Fri, 13 Nov 2009 00:00:00 +0100 3000731 http://www.medworm.com/index.php?rid=3000730&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19911302%26dopt%3DAbstract Authors: Green MM, Jain V Strong arguments can be found in the literature addressed to the question of the origin of homochirality in life, supporting the hypothesis that primordial life could have evolved in both homochiral forms and that early on when life was still rarely found, random events led to the survival of only one of these living mirror images. This proposal is an alternative to the generally accepted view that small enantiomeric excesses of biologically important molecules were amplified to homochirality prior to life's origin. Acceptance of the possibility of "two equal runners" leads to the importance of research investigations on routes to formation of ensembles of racemic mixtures of isotactic biologically interesting polymers, supramolecular entities and aggregates. ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3000730 Fri, 13 Nov 2009 00:00:00 +0100 3000730 http://www.medworm.com/index.php?rid=3000729&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19911303%26dopt%3DAbstract Authors: Breslow R, Levine M, Cheng ZL We show how the amino acids needed on prebiotic earth in their homochiral L form can be produced by a reaction of L-alpha-methyl amino acids-that have been identified in the Murchison meteorite-with alpha-keto acids under credible prebiotic conditions. When they are simply heated together they perform a process of decarboxylative transamination but with almost no chiral transfer, and that in the wrong direction, producing D-amino acids from the L-alpha-methyl amino acids. With copper ion a square planar complex with two of the reaction intermediates is formed, and now there is the desired L to L transformation, producing small enantioexcesses of the normal L-amino acids. We also show how these can be amplified, not by making more of the L form but... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3000729 Fri, 13 Nov 2009 00:00:00 +0100 3000729 http://www.medworm.com/index.php?rid=3000728&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19911304%26dopt%3DAbstract Authors: Mauksch M, Wei S, Freund M, Zamfir A, Tsogoeva SB The origin of the single chirality of most biomolecules is still a great puzzle. Carbohydrates could form in the formose reaction, which is proposed to be autocatalytic and contains aldol reaction steps. Based on our earlier observation of organoautocatalysis and spontaneous enantioenrichment in absence of deliberate chiral influences in the aldol reaction of acetone and p-nitrobenzaldehyde we suggest that a similar effect might be present also in the aldol reactions involved in gluconeogenesis. Herein we show that reactant precipitation observed in our earlier reported experiments does not affect the asymmetric autocatalysis in the aldol reaction we studied. We explain the phenomenon of spontaneous mirror symmetry breaking in ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=3000728 Fri, 13 Nov 2009 00:00:00 +0100 3000728 http://www.medworm.com/index.php?rid=2977987&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19899000%26dopt%3DAbstract Authors: Pizzarello S, Weber AL Glycolaldehyde and DL: -glyceraldehyde reacted in a water-buffered solution under mildly acidic conditions and in the presence of chiral dipeptide catalysts produced pentose sugars whose configuration is affected by the chirality of the catalyst. The chiral effect was found to vary between catalysts and to be largest for di-valine. Lyxose, arabinose, ribose and xylose are formed in different amounts, whose relative proportions do not change significantly with the varying of conditions. With LL: -peptide catalysts, ribose was the only pentose sugar to have a significant D: -enantiomeric excess (ee) (</=44%), lyxose displayed an L: -ee of </=66%, arabinose a smaller L: -ee of </=8%, and xylose was about racemic. These data expand our previous find... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2977987 Tue, 10 Nov 2009 00:00:00 +0100 2977987 http://www.medworm.com/index.php?rid=2977988&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19898951%26dopt%3DAbstract Authors: Macdermott AJ PMID: 19898951 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2977988 Sat, 07 Nov 2009 00:00:00 +0100 2977988 http://www.medworm.com/index.php?rid=2968144&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19890734%26dopt%3DAbstract Authors: Pizzarello S, Lahav M PMID: 19890734 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2968144 Fri, 06 Nov 2009 00:00:00 +0100 2968144 http://www.medworm.com/index.php?rid=2902085&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19830586%26dopt%3DAbstract Authors: Tessera M The research on the origin of life, as such, seems to have reached an impasse as a clear and universal scientific definition of life is probably impossible. On the contrary, the research on the origin of evolution may provide a clue. But it is necessary to identify the minimum requirements that allowed evolution to emerge on early Earth. The classical approach, the 'RNA world hypothesis' is one way, but an alternative based on nonlinear dynamics dealing with far-from-equilibrium self-organization and dissipative structures can also be proposed. The conditions on early Earth, near deep-sea hydrothermal sites, were favorable to the emergence of dissipative structures such as vesicles with bilayer membranes composed of a mixture of amphiphilic and hydrophobic molecules.... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2902085 Wed, 14 Oct 2009 23:00:00 +0100 2902085 http://www.medworm.com/index.php?rid=2810230&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19760521%26dopt%3DAbstract Authors: Schwartz AW PMID: 19760521 [PubMed - in process] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2810230 Sun, 20 Sep 2009 04:00:05 +0100 2810230 http://www.medworm.com/index.php?rid=2472153&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19468860%26dopt%3DAbstract Authors: PMID: 19468860 [PubMed - in process] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2472153 Fri, 12 Jun 2009 19:52:40 +0100 2472153 http://www.medworm.com/index.php?rid=2472128&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19472071%26dopt%3DAbstract Authors: Lindsey JS, Ptaszek M, Taniguchi M Porphyrins have long been proposed as key ingredients in the emergence of life yet plausible routes for forming their essential pyrrole precursor have heretofore not been identified. Here we show that the anaerobic reaction of delta-aminolevulinic acid (ALA, 1-5 mM) with the beta-ketoester methyl 4-methoxyacetoacetate (2-40 mM) in water (pH 5-7) at 70-100 degrees C for >6 h affords the porphyrinogen, which upon chemical oxidation gives the corresponding porphyrin in overall yield of up to 10%. The key intermediate is the alpha-methoxymethyl-substituted pyrrole, which undergoes tetramerization and macrocycle formation under kinetic control. The resulting type-I porphyrin bears four propionic acid and four carbomethoxy groups, is distinct fr... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2472128 Wed, 27 May 2009 04:00:00 +0100 2472128 http://www.medworm.com/index.php?rid=2472176&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19468859%26dopt%3DAbstract Authors: Griffith RW Among various scenarios that attempt to explain how life arose, the RNA world is currently the most widely accepted scientific hypothesis among biologists. However, the RNA world is logistically implausible and doesn't explain how translation arose and DNA became incorporated into living systems. Here I propose an alternative hypothesis for life's origin based on cooperation between simple nucleic acids, peptides and lipids. Organic matter that accumulated on the prebiotic Earth segregated into phases in the ocean based on density and solubility. Synthesis of complex organic monomers and polymerization reactions occurred within a surface hydrophilic layer and at its aqueous and atmospheric interfaces. Replication of nucleic acids and translation of peptides began a... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2472176 Tue, 26 May 2009 04:00:00 +0100 2472176 http://www.medworm.com/index.php?rid=2472191&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19387863%26dopt%3DAbstract Authors: Olsson-Francis K, de la Torre R, Towner MC, Cockell CS Cyanobacteria are photosynthetic organisms that have been considered for space applications, such as oxygen production in bioregenerative life support systems, and can be used as a model organism for understanding microbial survival in space. Akinetes are resting-state cells of cyanobacteria that are produced by certain genera of heterocystous cyanobacteria to survive extreme environmental conditions. Although they are similar in nature to endospores, there have been no investigations into the survival of akinetes in extraterrestrial environments. The aim of this work was to examine the survival of akinetes from Anabaena cylindrica in simulated extraterrestrial conditions and in Low Earth Orbit (LEO). Akinetes were dried o... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2472191 Wed, 22 Apr 2009 04:00:00 +0100 2472191 http://www.medworm.com/index.php?rid=2472208&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19370399%26dopt%3DAbstract Authors: Gleiser M, Walker SI The activation-polymerization-epimerization-depolymerization (APED) model of Plasson et al. has recently been proposed as a mechanism for the evolution of homochirality on prebiotic Earth. The dynamics of the APED model in two-dimensional spatially-extended systems is investigated for various realistic reaction parameters. It is found that the APED system allows for the formation of isolated homochiral proto-domains surrounded by a racemate. A diffusive slowdown of the APED network induced, for example, through tidal motion or evaporating pools and lagoons leads to the stabilization of homochiral bounded structures as expected in the first self-assembled protocells. PMID: 19370399 [PubMed - as supplied by publisher] (Source: Origins of Life and Evoluti... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2472208 Thu, 16 Apr 2009 04:00:00 +0100 2472208 http://www.medworm.com/index.php?rid=2295643&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19308669%26dopt%3DAbstract Authors: Macdermott AJ, Fu T, Nakatsuka R, Coleman AP, Hyde GO In 1996, four alpha-methyl amino acids in the Murchison meteorite-L-isovaline, L-alpha-methylnorvaline, L-alpha-methyl-allo-isoleucine and L-alpha-methyl-isoleucine-were found to show significant enantiomeric excesses of the L form, ranging from 2% to 9%. Their deuterium to hydrogen isotope ratios suggest they formed in the pre-solar interstellar gas cloud rather than during a later aqueous processing phase on the asteroid parent body. In this paper we apply the techniques of the preceding two papers to compute the parity-violating energy shifts of these amino acids. We find that, in the gas phase, the PVESs of the neutral L forms of all four Murchison alpha-methyl amino acids are decisively negative, and there is even some... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2295643 Tue, 24 Mar 2009 04:00:00 +0100 2295643 http://www.medworm.com/index.php?rid=2283559&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19301141%26dopt%3DAbstract Authors: Maury CP The idea is advanced that under the extreme earth conditions for ~3.9 billions years ago, protein-based beta-sheet molecular structures were the first self-propagating and information-processing biomolecules that evolved. The amyloid structure of these aggregates provided an effective protection against the harsh conditions known to decompose both polyribonucleotides and natively folded polypeptides. In the prebiotic amyloid world, both the replicative and informational functions were carried out by structurally stable beta-sheet protein aggregates in a prion-like mode involving templated self-propagation and storage of information in the beta-sheet conformation. In this amyloid (protein)-first, hybrid replication-metabolism view, the synthesis of RNA, and the evolvem... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2283559 Fri, 20 Mar 2009 04:00:00 +0100 2283559 http://www.medworm.com/index.php?rid=2283561&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19291419%26dopt%3DAbstract We present new computations of gas-phase amino acids PVESs, using partial optimizations with small basis sets, and the results agree well with those from higher level techniques. In the following paper we apply these less costly techniques to larger amino acids. The "conformation problem" has led some to dismiss the PVES as the source of life's handedness, but we believe this is premature: we show here that amino acids are a special case because their favoured conformations are almost achiral. PMID: 19291419 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2283561 Tue, 17 Mar 2009 04:00:00 +0100 2283561 http://www.medworm.com/index.php?rid=2283557&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19301142%26dopt%3DAbstract We present new coupled-perturbed Hartree-Fock (CPHF) and density functional theory (DFT) computations of the parity-violating energy difference (PVED) between enantiomers for H(2)O(2) and H(2)S(2). Our DFT PVED computations are the first for H(2)S(2) and the first with the new HCTH and OLYP functionals. Like other "second generation" PVED computations, our results are an order of magnitude larger than the original "first generation" uncoupled-perturbed Hartree-Fock computations of Mason and Tranter. We offer an explanation for the dramatically larger size in terms of cancellation of contributions of opposing signs, which also explains the basis set sensitivity of the PVED, and its conformational hypersensitivity (addressed in the following paper). This paper also serves as a review of the ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2283557 Tue, 17 Mar 2009 04:00:00 +0100 2283557 http://www.medworm.com/index.php?rid=2241790&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19259781%26dopt%3DAbstract Authors: Summers DP, Noveron J, Basa RC Amphiphilic bilayer membrane structures (vesicles) have been postulated to have been abiotically formed and spontaneously assemble on the prebiotic Earth, providing compartmentalization for the origin of life. These vesicles are similar to modern cellular membranes and can serve to contain water-soluble species, concentrate species, and have the potential to catalyze reactions. The origin of the use of photochemical energy in metabolism (i.e. energy transduction) is one of the central issues in the origin of life. This includes such questions as how energy transduction may have occurred before complex enzymatic systems, such as required by contemporary photosynthesis, had developed and how simple a photochemical system is possible. It has been po... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2241790 Wed, 04 Mar 2009 05:00:00 +0100 2241790 http://www.medworm.com/index.php?rid=2157247&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19184520%26dopt%3DAbstract Special Issue: Abstracts from the Eighth European Workshop on Astrobiology, Neuchâtel, Switzerland, 1-3 September, 2008. Orig Life Evol Biosph. 2009 Jan 31; Authors: PMID: 19184520 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2157247 Sat, 31 Jan 2009 05:00:00 +0100 2157247 http://www.medworm.com/index.php?rid=2125891&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19156532%26dopt%3DAbstract Authors: Wallace R Mutualism, obligate mutualism, symbiosis, and the eukaryotic 'fusion' of Serial Endosymbiosis Theory represent progressively more rapid and less distorted real-time communication between biological structures instantiating information sources. Such progression in accurate information transmission requires, in turn, progressively greater channel capacity that, through the homology between information source uncertainty and free energy density, requires ever more energetic metabolism. The eukaryotic transition, according to this model, may have been entrained by an ecosystem resilience shift from anaerobic to aerobic metabolism. PMID: 19156532 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2125891 Wed, 21 Jan 2009 05:00:00 +0100 2125891 http://www.medworm.com/index.php?rid=2112634&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19148771%26dopt%3DAbstract Authors: Najafpour MM The recently published X-ray absorption fine structure of photosystem II provides a more detailed architecture of the oxygen-evolving complex (OEC) and the surrounding amino acids. In this paper, a comparison between manganese superoxide dismutase, dinuclear manganese catalase enzymes and the oxygen evolving complex in photosystem II is reported. The author suggests that the development of oxygenic photosynthesis occurred in steps, the first of which involved only one manganese ion (Mn(II)) that oxidized two water molecules to hydrogen peroxide and then oxygen. PMID: 19148771 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=2112634 Fri, 16 Jan 2009 05:00:00 +0100 2112634 http://www.medworm.com/index.php?rid=1997098&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19037745%26dopt%3DAbstract Authors: Cleaves HJ, Aubrey AD, Bada JL It has been proposed that oligopeptides may be formed in submarine hydrothermal systems (SHSs). Oligopeptides have been synthesized previously under simulated SHS conditions which are likely geochemically implausible. We have herein investigated the oligomerization of glycine under SHS-like conditions with respect to the limitations imposed by starting amino acid concentration, heating time, and temperature. When 10(-1) M glycine solutions were heated at 250 degrees C for < 20 min glycine oligomers up to tetramers and diketopiperazine (DKP) were detectable. At 200 degrees C, less oligomerization was noted. Peptides beyond glycylglycine (gly(2)) and DKP were not detected below 150 degrees C. At 10(-2) M initial glycine concentration and below, ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1997098 Thu, 27 Nov 2008 05:00:00 +0100 1997098 http://www.medworm.com/index.php?rid=1997099&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19034685%26dopt%3DAbstract We report here the results of experiments exploring the potential for amino acid synthesis at high temperature from synthetic seawater solutions of varying composition. The synthesis of amino acids was examined as a function of temperature, heating time, starting material composition and concentration. Using very favorable reactant conditions (high concentrations of reactive, reduced species), small amounts of a limited set of amino acids are generated at moderate temperature conditions ( approximately 125-175 degrees C) over short heating times of a few days, but even these products are significantly decomposed after exposure times of approximately 1 week. The high concentration dependence observed for these synthetic reactions are demonstrated by the fact that a 10-fold drop in concentra... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1997099 Wed, 26 Nov 2008 05:00:00 +0100 1997099 http://www.medworm.com/index.php?rid=1952744&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18998238%26dopt%3DAbstract Authors: Jalbout AF The prebiotic possibilities for the synthesis of interstellar carbohydrates through a protic variant of the formose reaction under gas phase conditions were studied. Ab initio calculations were used to evaluate potential mechanisms. Based on considerations of barrier heights and temperature variations in the Interstellar Medium the plausibility of extended sugar synthesis will be discussed. PMID: 18998238 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1952744 Sat, 08 Nov 2008 05:00:00 +0100 1952744 http://www.medworm.com/index.php?rid=1930701&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18979177%26dopt%3DAbstract Authors: Gusev GA, Kobayashi K, Moiseenko EV, Poluhina NG, Saito T, Ye T, Tsarev VA, Xu J, Huang Y, Zhang G Results of the second stage of the RAMBAS (RAdiation Mechanism of Biomolecular ASymmetry) experiment on investigation of the radiation mechanism of the influence on chiral molecules are presented. Optical activity of samples of racemic mixtures of amino acids with heavy metals was compared prior to and after irradiation by electron flux from a radioactive source. It is found that the irradiation results in asymmetric degradation of both complexes and amino acids and in production of chiral asymmetry of the samples under study. These results confirm the conclusions inferred from the first stage of the RAMBAS experiment and could be important for the solution of the origin-of-life ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1930701 Sat, 01 Nov 2008 04:00:00 +0100 1930701 http://www.medworm.com/index.php?rid=1886948&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18925425%26dopt%3DAbstract Authors: Zaia DA, Zaia CT, De Santana H The adsorption of amino acids on minerals and their condensation under conditions that resemble those of prebiotic earth is a well studied subject. However, which amino acids should be used in these experiments is still an open question. The main goal of this review is to attempt to answer this question. There were two sources of amino acids for the prebiotic earth: (1) exogenous-meaning that the amino acids were synthesized outside the earth and delivered to our planet by interplanetary dust particles (IDPs), meteorites, comets, etc. and (2) endogenous-meaning that they were synthesized on earth in atmospheric mixtures, hydrothermal vents, etc. For prebiotic chemistry studies, the use of a mixture of amino acids from both endogenous and exogenou... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1886948 Fri, 17 Oct 2008 04:00:00 +0100 1886948 http://www.medworm.com/index.php?rid=1880577&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18855114%26dopt%3DAbstract Authors: Cirković MM, Vukotić B Can astrophysics explain Fermi's paradox or the "Great Silence" problem? If available, such explanation would be advantageous over most of those suggested in literature which rely on unverifiable cultural and/or sociological assumptions. We suggest, instead, a general astrobiological paradigm which might offer a physical and empirically testable paradox resolution. Based on the idea of James Annis, we develop a model of an astrobiological phase transition of the Milky Way, based on the concept of the global regulation mechanism(s). The dominant regulation mechanisms, arguably, are gamma-ray bursts, whose properties and cosmological evolution are becoming well-understood. Secular evolution of regulation mechanisms leads to the brief epoch of p... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1880577 Wed, 15 Oct 2008 04:00:00 +0100 1880577 http://www.medworm.com/index.php?rid=1876703&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18853276%26dopt%3DAbstract We present here a computational comparison of full genomes from 13 diverse organisms from the Archaea, Bacteria, and Eucarya to identify genetic sequences conserved across the widest divisions of life. Our results identify the 16S and 23S ribosomal RNA genes as well as other universally conserved nucleotide sequences in genes encoding particular classes of transfer RNAs and within the nucleotide binding domains of ABC transporters as the most conserved DNA sequence segments across phylogeny. This set of sequences defines a core set of DNA regions that have changed the least over billions of years of evolution and provides a means to identify and classify divergent life, including ancestrally related life on other planets. PMID: 18853276 [PubMed - as supplied by publisher] (Source: Orig... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1876703 Tue, 14 Oct 2008 04:00:00 +0100 1876703 http://www.medworm.com/index.php?rid=1863329&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18841492%26dopt%3DAbstract Authors: Gleiser M, Thorarinson J, Walker SI Most biomolecules occur in mirror, or chiral, images of each other. However, life is homochiral: proteins contain almost exclusively L-amino acids, while only D-sugars appear in RNA and DNA. The mechanism behind this fundamental asymmetry of life remains an open problem. Coupling the spatiotemporal evolution of a general autocatalytic polymerization reaction network to external environmental effects, we show through a detailed statistical analysis that high intensity and long duration events may drive achiral initial conditions towards chirality. We argue that life's homochirality resulted from sequential chiral symmetry breaking triggered by environmental events, thus extending the theory of punctuated equilibrium to the prebiotic realm. Ap... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1863329 Wed, 08 Oct 2008 04:00:00 +0100 1863329 http://www.medworm.com/index.php?rid=1776013&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18777105%26dopt%3DAbstract Authors: Wallace R, Wallace RG We reexamine Eigen's paradox using the asymptotic limit theorems of information theory. Applying the homology between information source uncertainty and free energy density, under rate distortion constraints, the error catastrophe emerges as the lowest energy state for simple prebiotic systems without error correction. Invoking the usual compartmentalization - i.e., 'vesicles' - and using a Red Queen argument, suggests that information crosstalk between two or more properly interacting structures can initiate a coevolutionary dynamic having at least two quasi-stable states. The first is a low energy realm near the error threshold, and, depending on available energy, the second can approach zero error as a limit. A large deviations argument produces jet-li... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1776013 Sat, 06 Sep 2008 04:00:00 +0100 1776013 http://www.medworm.com/index.php?rid=1747348&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18726708%26dopt%3DAbstract Authors: Lazcano A, Bada JL An appreciation of Stanley L. Miller, the pioneer prebiotic chemist, who died last year. PMID: 18726708 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1747348 Tue, 26 Aug 2008 04:00:00 +0100 1747348 http://www.medworm.com/index.php?rid=1638083&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18636340%26dopt%3DAbstract Authors: Wu M, Higgs PG Genetic inheritance in modern cells is due to template-directed replication of nucleic acids. However, the difficulty of prebiotic synthesis of long information-carrying polymers like RNA raises the question of whether some other form of heredity is possible without polymers. As an alternative, the lipid world theory has been proposed, which considers non-covalent assemblies of lipids, such as micelles and vesicles. Assemblies store information in the form of a non-random molecular composition, and this information is passed on when the assemblies divide, i.e. the assemblies show compositional inheritance. Here, we vary several important assumptions of previous lipid world models and show that compositional inheritance is relevant more generally than the context... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1638083 Fri, 18 Jul 2008 04:00:00 +0100 1638083 http://www.medworm.com/index.php?rid=1552335&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18581252%26dopt%3DAbstract Authors: Weber AL Reaction of glyceraldehyde with alanine amide (or ammonia) under anaerobic aqueous conditions yielded 3,5(6)-dimethylpyrazin-2-one that is considered a possible complementary residue of a primitive replicating molecule that preceded RNA. Synthesis of the dimethylpyrazin-2-one isomers under mild aqueous conditions (65 degrees C, pH 5.5) from 100 mM glyceraldehyde and alanine amide (or ammonia) was complete in about 5 days. This synthesis using 25 mM glyceraldehyde and alanine amide gave a total pyrazinone yield of 9.3% consisting of 42% of the 3,5-dimethylprazin-2-one isomer and 58% of the 3,6-dimethylpyrazin-2-one isomer. The related synthesis of the dimethylpyrazin-2-one isomers from glyceraldehyde and ammonia was about 200-fold less efficient than the alanine amide ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1552335 Thu, 26 Jun 2008 04:00:00 +0100 1552335 http://www.medworm.com/index.php?rid=1544487&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18574710%26dopt%3DAbstract Authors: Larowe DE, Regnier P The thermodynamic potential for the abiotic synthesis of the five common nucleobases (adenine, cytosine, guanine, thymine, and uracil) and two monosaccharides (ribose and deoxyribose) from formaldehyde and hydrogen cyanide has been quantified under temperature, pressure, and bulk composition conditions that are representative of hydrothermal systems. The activities of the precursor molecules (formaldehyde and hydrogen cyanide) required to evaluate the thermodynamics of biomolecule synthesis were computed using the concentrations of aqueous N(2), CO, CO(2) and H(2) reported in the modern Rainbow hydrothermal system. The concentrations of precursor molecules that can be synthesized are strongly dependent on temperature with larger concentrations prevailing a... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1544487 Tue, 24 Jun 2008 04:00:00 +0100 1544487 http://www.medworm.com/index.php?rid=1536070&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18566911%26dopt%3DAbstract Authors: Parkinson CD, Liang MC, Yung YL, Kirschivnk JL The prolific activity and presence of a plume on Saturn's tiny moon Enceladus offers us a unique opportunity to sample the interior composition of an icy satellite, and to look for interesting chemistry and possible signs of life. Based on studies of the potential habitability of Jupiter's moon Europa, icy satellite oceans can be habitable if they are chemically mixed with the overlying ice shell on Myr time scales. We hypothesize that Enceladus' plume, tectonic processes, and possible liquid water ocean may create a complete and sustainable geochemical cycle that may allow it to support life. We discuss evidence for surface/ocean material exchange on Enceladus based on the amounts of silicate dust material present in the Enceladu... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1536070 Fri, 20 Jun 2008 04:00:00 +0100 1536070 http://www.medworm.com/index.php?rid=1532191&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18560991%26dopt%3DAbstract Authors: Namani T, Deamer DW The first forms of cellular life required a source of amphiphilic compounds capable of assembling into stable boundary structures. Membranes composed of fatty acids have been proposed as model systems of primitive membranes, but their bilayer structure is stable only within a narrow pH range and low ionic strength. They are particularly sensitive to aggregating effects of divalent cations (Mg(+2), Ca(+2), Fe(+2)) that would be present in Archaean sea water. Here we report that mixtures of alkyl amines and fatty acids form vesicles at strongly basic and acidic pH ranges which are resistant to the effects of divalent cations up to 0.1 M. Vesicles formed by mixtures of decylamine and decanoic acid (1:1 mole ratio) are relatively permeable to pyranine, a fluore... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1532191 Tue, 17 Jun 2008 04:00:00 +0100 1532191 http://www.medworm.com/index.php?rid=1494795&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18523859%26dopt%3DAbstract Authors: de Vera JP, Rettberg P, Ott S Lichens are described as a symbiosis formed by a myco- and photobiont, capable of colonizing habitats where their separate symbionts would not be able to survive. Space simulation studies on the separated symbionts of the lichen Xanthoria elegans have been performed to test their capacity to resist the most extreme conditions. The isolated cultured symbiont cells were exposed to different doses of the UV spectrum, and to vacuum. Cultures of both symbionts were analysed by specific vitality tests (LIVE/DEAD-staining detected by Confocal Laser Scanning Microscopy). Growth capacity of symbiont cultures on different media was analysed after exposure to extreme environmental stresses. The data obtained support the hypothesis that the symbiotic state co... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1494795 Wed, 04 Jun 2008 04:00:00 +0100 1494795 http://www.medworm.com/index.php?rid=1492521&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18521718%26dopt%3DAbstract Authors: Melkikh AV, Seleznev VD Early stages of the evolution of life are considered in terms of control theory. A model is proposed for the transport of substances in a protocell possessing the property of robustness with regard to changes in the environmental concentration of a substance. PMID: 18521718 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1492521 Tue, 03 Jun 2008 04:00:00 +0100 1492521 http://www.medworm.com/index.php?rid=1492520&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18521719%26dopt%3DAbstract Authors: Barabás B, Caglioti L, Micskei K, Zucchi C, Pályi G Natural-abundance isotopic substitution in isotopically prochiral groups of otherwise achiral molecules can provide stochastically formed enantiomeric excesses which exceed the sensitivity threshold of sensitive asymmetric autocatalytic (Soai-type) reactions. This kind of induction of chirality should be taken into consideration in in vitro model experiments and offer a new kind of entry into primary prebiotic or early biotic enantioselection in the earliest stages of molecular evolution. PMID: 18521719 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1492520 Tue, 03 Jun 2008 04:00:00 +0100 1492520 http://www.medworm.com/index.php?rid=1434028&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18465201%26dopt%3DAbstract Authors: Gleiser M, Walker SI A generalized autocatalytic model for chiral polymerization is investigated in detail. Apart from enantiomeric cross-inhibition, the model allows for the autogenic (non-catalytic) formation of left and right-handed monomers from a substrate with reaction rates epsilon ( L ) and epsilon ( R ), respectively. The spatiotemporal evolution of the net chiral asymmetry is studied for models with several values of the maximum polymer length, N. For N = 2, we study the validity of the adiabatic approximation often cited in the literature. We show that the approximation obtains the correct equilibrium values of the net chirality, but fails to reproduce the short time behavior. We show also that the autogenic term in the full N = 2 model behaves as a control paramete... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1434028 Fri, 09 May 2008 04:00:00 +0100 1434028 http://www.medworm.com/index.php?rid=1418693&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18452061%26dopt%3DAbstract Authors: Wander MC, Kubicki JD, Schoonen MA Nitrogen reduction by ferrous iron has been suggested as an important mechanism in the formation of ammonia on pre-biotic Earth. This paper examines the effects of adsorption of ferrous iron onto a goethite (alpha-FeOOH) substrate on the thermodynamic driving force and rate of a ferrous iron-mediated reduction of N(2) as compared with the homogeneous aqueous reaction. Utilizing density functional theory and Marcus Theory of proton coupled electron transfer reactions, the following two reactions were studied: [Formula: see text]and [Formula: see text]Although the rates of both reactions were calculated to be approximately zero at 298 K, the model results suggest that adsorption alters the thermodynamic driving force for the reaction but has no... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1418693 Fri, 02 May 2008 04:00:00 +0100 1418693 http://www.medworm.com/index.php?rid=1374115&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18409029%26dopt%3DAbstract Authors: Hatton B, Rickard D In the hydrothermal FeS-world origin of life scenarios nucleic acids are suggested to bind to iron (II) monosulphide precipitated from the reaction between hydrothermal sulphidic vent solutions and iron-bearing oceanic water. In lower temperature systems, the first precipitate from this process is nanoparticulate, metastable FeS(m) with a mackinawite structure. Although the interactions between bulk crystalline iron sulphide minerals and nucleic acids have been reported, their reaction with nanoparticulate FeS(m) has not previously been investigated. We investigated the binding of different nucleic acids, and their constituents, to freshly precipitated, nanoparticulate FeS(m). The degree to which the organic molecules interacted with FeS(m) is chromosomal D... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1374115 Sun, 13 Apr 2008 04:00:00 +0100 1374115 http://www.medworm.com/index.php?rid=1350088&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18386156%26dopt%3DAbstract Authors: Kolesnikov MP, Telegina TA, Lyudnikova TA, Kritsky MS A model for abiogenic photophosphorylation of ADP by orthophosphate to yield ATP was studied. The model is based on the photochemical activity of flavoproteinoid microspheres that are formed by aggregation in an aqueous medium of products of thermal condensation of a glutamic acid, glycine and lysine mixture (8:3:1) and contain, along with amino acid polymers (proteinoids), abiogenic isoalloxazine (flavin) pigments. Irradiation of aqueous suspensions of microspheres with blue visible light or ultraviolet in the presence of ADP and orthophosphate resulted in ATP formation. The yield of ATP in aerated suspensions was 10-20% per one mol of starting ADP. Deaeration reduced the photophosphorylating activity of microspheres five ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1350088 Wed, 02 Apr 2008 04:00:00 +0100 1350088 http://www.medworm.com/index.php?rid=1319743&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18351439%26dopt%3DAbstract Discussion: Differential Rates of D: - and L: -tyrosine Crystallization. Orig Life Evol Biosph. 2008 Mar 20; Authors: Shinitzky M, Deamer D We earlier reported that we had observed quantifiable differences in crystallization rates of D: and L: tyrosine. It has been suggested that these results were due to the presence of impurities. Here we argue that it is premature to conclude that impurities entirely explain the results. More generally, there is an accumulating weight of evidence that D: and L: enantiomers display unexpected differences in their physical properties and behavior. These should be taken into account as we attempt to understand the origin of biochirality. PMID: 18351439 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphe... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1319743 Thu, 20 Mar 2008 04:00:00 +0100 1319743 http://www.medworm.com/index.php?rid=1311696&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18344011%26dopt%3DAbstract Authors: Lambert JF The present paper offers a review of recent (post-1980) work on amino acid adsorption and thermal reactivity on oxide and sulfide minerals. This review is performed in the general frame of evaluating Bernal's hypothesis of prebiotic polymerization in the adsorbed state, but written from a surface scientist's point of view. After a general discussion of the thermodynamics of the problem and exactly what effects surfaces should have to make adsorbed-state polymerization a viable scenario, we examine some practical difficulties in experimental design and their bearing on the conclusions that can be drawn from extant works, including the relevance of the various available characterization techniques. We then present the state of the art concerning the mechanisms of the ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1311696 Sat, 15 Mar 2008 04:00:00 +0100 1311696 http://www.medworm.com/index.php?rid=1265493&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18302005%26dopt%3DAbstract Authors: Burkov VI, Goncharova LA, Gusev GA, Kobayashi K, Moiseenko EV, Poluhina NG, Saito T, Tsarev VA, Xu J, Zhang G The first results of the RAdiation Mechanism of Biomolecular ASymmetry (RAMBAS) experiment on investigation of the radiation mechanism of the influence on chiral molecules, as a factor leading to origination of chiral asymmetry are presented. It was found that irradiation of simple achiral materials by a flux of electrons from radioactive source initiated the synthesis of amino acids, and it resulted in asymmetric degradation and chiral asymmetry in a racemic mixture of amino acids. The results obtained can be important for the solution of the origin-of-life and biological homochirality problems. PMID: 18302005 [PubMed - as supplied by publisher] (Source: Origins o... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1265493 Wed, 27 Feb 2008 05:00:00 +0100 1265493 http://www.medworm.com/index.php?rid=1258985&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18297413%26dopt%3DAbstract Authors: Franiatte M, Richard L, Elie M, Nguyen-Trung C, Perfetti E, Larowe DE An experimental study has been carried out on the stability of adenine (one of the five nucleic acid bases) under hydrothermal conditions. The experiments were performed in sealed autoclaves at 300 degrees C under fugacities of CO(2), N(2) and H(2) supposedly representative of those in marine hydrothermal systems on the early Earth. The composition of the gas phase was obtained from the degradation of oxalic acid, sodium nitrite and ammonium chloride, and the oxidation of metallic iron. The results of the experiments indicate that after 200 h, adenine is still present in detectable concentration in the aqueous phase. In fact, the concentration of adenine does not seem to be decreasing after approximately 24 ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1258985 Sat, 23 Feb 2008 05:00:00 +0100 1258985 http://www.medworm.com/index.php?rid=1250587&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18288587%26dopt%3DAbstract Authors: Ji F, Zhou H, Yang Q Conversion of CO(2) to organic compounds in hydrothermal systems is important in understanding prebiotic chemical evolution leading to the origin of life. However, organic compounds with carbon number of more than 3 have never been produced from dissolved CO(2) in simulated hydrothermal experiments. In this paper, we report that not only CH(4), C(2)H(6) and C(3)H(8), but also n-C(4)H(10) and n-C(5)H(12) could be produced from dissolved CO(2) and H(2) in the presence of cobalt-bearing magnetite at 300 degrees C and 30 MPa. It is shown that unbranched alkanes in Anderson-Schulz-Flory distribution were the dominant hydrocarbon products produced from dissolved CO(2) catalyzed by cobalt-bearing magnetite under certain hydrothermal conditions. It is proposed tha... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1250587 Thu, 21 Feb 2008 05:00:00 +0100 1250587 http://www.medworm.com/index.php?rid=1215676&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18253860%26dopt%3DAbstract In this study, we attempted to produce ammonia from N(2) by oxidizing white rust both photochemically and in a dark reaction. All results indicated the reaction was inhibited by competing reactions; primarily the reduction of H(2)O to H(2). However, the dark reactions showed limited potential for reduction up to 1.4 mM. As a result, we turned to the question of closure temperature; the minimum temperature of rapid reaction based on a choice of reductant, which we demonstrate a model for its estimation. Due to the high thermodynamic energy of the [Formula: see text] intermediate, we conclude that aqueous photochemical reduction under the conditions studied here is an unlikely prebiotic source for reactive, i.e. reduced, nitrogen. PMID: 18253860 [PubMed - as supplied by publisher] (Sourc... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1215676 Wed, 06 Feb 2008 05:00:00 +0100 1215676 http://www.medworm.com/index.php?rid=1189042&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18228159%26dopt%3DAbstract Authors: Jalasvuori M, Bamford JK Viruses and cells co-evolve due to the parasitic nature of viruses. Yet there are no models suggesting how the unicellular organisms and their viruses might co-evolve structurally. Here, in this study, we plunge into this unexplored field from a wide perspective and try to describe some of the intriguing ways in which viruses may have shaped the cellular life forms on the ancient Earth. At first we propose a scenario where viruses act as a driving force in the emergence of bacterial cell walls by providing favorable intermediates for the otherwise improbable steps in the cell wall generation. We also discuss the role of viruses in the evolution of cell surface components such as receptors and second membranes. Finally we focus on hypothetical proto-vir... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1189042 Tue, 29 Jan 2008 05:00:00 +0100 1189042 http://www.medworm.com/index.php?rid=1179784&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18219586%26dopt%3DAbstract Authors: Goldberg SI On the occasions when D-tyrosine is observed to crystallize faster than its L-enantiomer, it is the result of a diastereomeric interaction between an airborne, non-racemic, chiral influence-probably a fungal spore-and the tyrosine enantiomers, enhancing the degree of crystal nucleation of D-tyrosine over L-tyrosine. This explanation, supported by experimental evidence, is presented as a more plausible alternative to the Shinitzky-Deamer hypothesis (Shinitzky et al., Progress in biological chirality, Elsevier, Amsterdam, pp. 329-337, 2004; Deamer et al., Chirality, 19:751-763, 2007) which relies on the parity violation energy difference between enantiomers, a femtojoule to picojoule per mole theoretical energy range. PMID: 18219586 [PubMed - as supplied by publi... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1179784 Fri, 25 Jan 2008 05:00:00 +0100 1179784 http://www.medworm.com/index.php?rid=1170656&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18204914%26dopt%3DAbstract Authors: Cleaves HJ, Chalmers JH, Lazcano A, Miller SL, Bada JL The action of an electric discharge on reduced gas mixtures such as H(2)O, CH(4) and NH(3) (or N(2)) results in the production of several biologically important organic compounds including amino acids. However, it is now generally held that the early Earth's atmosphere was likely not reducing, but was dominated by N(2) and CO(2). The synthesis of organic compounds by the action of electric discharges on neutral gas mixtures has been shown to be much less efficient. We show here that contrary to previous reports, significant amounts of amino acids are produced from neutral gas mixtures. The low yields previously reported appear to be the outcome of oxidation of the organic compounds during hydrolytic workup by nitrite and n... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1170656 Sat, 19 Jan 2008 05:00:00 +0100 1170656 http://www.medworm.com/index.php?rid=1147130&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18188676%26dopt%3DAbstract Authors: Jalbout AF, Shipar MA The possibility of the occurrence of the nonenzymatic browning reaction in the gaseous phase in the interstellar medium has been investigated by using Density Functional Theory computations. Mechanisms for the reactions between formaldehyde (Fald) + glycine (Gly), Fald + NH (3) and Fald + methylamine (MeAm) have been proposed, and the possibility of the formation of different compounds in the proposed mechanisms has been evaluated through calculating the Gibb's free energy changes for different steps of the reaction, by following the total mass balance. The Fald + Gly reaction under basic conditions is found as the most favorable for producing 1-methyl-amino methene or 1-methyl-amino methelene (MAM). The reaction under acidic conditions is found to be the... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1147130 Fri, 11 Jan 2008 05:00:00 +0100 1147130 http://www.medworm.com/index.php?rid=1131843&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18175206%26dopt%3DAbstract This study shows that in all experiments amino acids are formed. Their total quantities and distribution depend slightly on the experimental parameters explored in the present work, the important requirement to form such molecules being that the starting ice mixtures must contain the four elements C, H, O and N. We also discuss the effects of the chemical treatment needed to detect and identify the amino acids in the organic residues. Finally, these results are compared with meteoritic amino acid data from the carbonaceous chondrite Murchison, and the formation processes of such compounds under astrophysical conditions are discussed. PMID: 18175206 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1131843 Fri, 04 Jan 2008 05:00:00 +0100 1131843 http://www.medworm.com/index.php?rid=1109982&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18095184%26dopt%3DAbstract Authors: Schwartz AW PMID: 18095184 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1109982 Wed, 19 Dec 2007 05:00:00 +0100 1109982 http://www.medworm.com/index.php?rid=1048068&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18034367%26dopt%3DAbstract Authors: Janda M, Morvova M, Machala Z, Morva I The chemistry induced by atmospheric pressure DC discharges above a water surface in CO(2)/N(2)/H(2)O mixtures was investigated. The gaseous mixtures studied represent a model prebiotic atmosphere of the Earth. The most remarkable changes in the chemical composition of the treated gas were the decomposition of CO(2) and the production of CO. The concentration of CO increased logarithmically with the increasing input energy density and an increasing initial concentration of CO(2) in the gas. The highest achieved concentration of CO was 4.0 +/- 0.6 vol. %. The production of CO was crucial for the synthesis of organic species, since reactions of CO with some reactive species generated in the plasma, e. g. H[Formula: see text] or N[Formula: s... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1048068 Fri, 23 Nov 2007 05:00:00 +0100 1048068 http://www.medworm.com/index.php?rid=1033721&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D18008180%26dopt%3DAbstract Authors: Rajamani S, Vlassov A, Benner S, Coombs A, Olasagasti F, Deamer D A fundamental problem in research on the origin of life is the process by which polymers capable of catalysis and replication were produced on the early Earth. Here we show that RNA-like polymers can be synthesized non-enzymatically from mononucleotides in lipid environments. The RNA-like polymers were initially identified by nanopore analysis, a technique with single molecule sensitivity. To our knowledge, this is the first such application of a nanopore instrument to detect RNA synthesis under simulated prebiotic conditions. The synthesis of the RNA-like polymers was confirmed by standard methods of enzymatic end labeling followed by gel electrophoresis. Chemical activation of the mononucleotides is not requir... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=1033721 Fri, 16 Nov 2007 05:00:00 +0100 1033721 http://www.medworm.com/index.php?rid=990095&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17965945%26dopt%3DAbstract Authors: Schwartz AW PMID: 17965945 [PubMed - as supplied by publisher] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=990095 Sat, 27 Oct 2007 04:00:00 +0100 990095 http://www.medworm.com/index.php?rid=984311&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17592753%26dopt%3DAbstract Authors: Strazewski P We have not yet reached a generally accepted view on how the genetic code might have originated. What has been proposed so far? The main part of the contribution to the panel discussion was devoted to recall to the audience the chronological order of publications the main aim of which it was, at least theoretically, to somehow connect physico-chemical properties of physically proximal 'universal adapters', usually some kind of nucleic acid polymer, with reactive forms of physically proximal amino acids that would subsequently polymerise into polypeptides. PMID: 17592753 [PubMed - in process] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=984311 Mon, 01 Oct 2007 04:00:00 +0100 984311 http://www.medworm.com/index.php?rid=984310&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17592754%26dopt%3DAbstract Authors: Svetina S The question "What was the minimum number of genes necessary in the early cell" is rephrased as "Is it feasible to assume that early cells had no genes?" It is shown that a kind of primitive life process could exist on the basis only of properties specific to vesicles, and that it would have the potential to evolve into more complex cell-like processes. PMID: 17592754 [PubMed - in process] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=984310 Mon, 01 Oct 2007 04:00:00 +0100 984310 http://www.medworm.com/index.php?rid=984309&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17592755%26dopt%3DAbstract Authors: Edwards HG The recognition of extinct or extant life signatures in the terrestrial geological record is fundamentally dependent upon the understanding of both the structural morphology and chemical composition of relict biomaterials; the identification of cyanobacterial colonies that have adapted biogeologically their mineral matrices in early evolutionary processes is a fundamental step in the acquisition of analytical data from remote planetary probes designed for life-detection experiments, particularly on Mars and on the planetary satellite moons, Europa and Titan. A key factor in the assessment of early life signatures is the molecular presence of chemicals designed to protect the emerging organisms from the damaging effect of radiation exposure and of desiccation and tem... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=984309 Mon, 01 Oct 2007 04:00:00 +0100 984309 http://www.medworm.com/index.php?rid=984308&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17592756%26dopt%3DAbstract Authors: Raulin F For understanding the origin(s) of life on Earth it is essential to search for and study extraterrestrial environments where some of the processes which participated in the emergence of Life on our planet are still occurring. This is one of the goals of astrobiology. In that frame, the study of extraterrestrial organic matter is essential and is certainly not of limited interest regarding prebiotic molecular evolution. Titan, the largest satellite of Saturn and the only planetary body with an atmosphere similar to that of the Earth is one of the places of prime interest for these astrobiological questions. It presents many analogies with the primitive Earth, and is a prebiotic-like laboratory at the planetary scale, where a complex organic chemistry in is currently go... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=984308 Mon, 01 Oct 2007 04:00:00 +0100 984308 http://www.medworm.com/index.php?rid=984307&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17592757%26dopt%3DAbstract Authors: Zagorski ZP In the answer to major questions of astrobiology and chirality, the panspermia-hypothesis is often discussed as the only proposal of transportation of life to the Earth. On the basis of the known presence of ionizing radiation in the space, assumed on the level calculated by Clark (Orig Life Evol Biosph 31:185-197, 2001), the hypothesis is rejected as the explanation of origins of life on Earth. In fact, comparatively low doses of radiation sterilize irreversibly all biological material. Sufficiently long sojourn in space of objects containing prebiotic chemical blocks also does not contribute to the origins of life on Earth, because of elimination of homochirality, if any, and of radiation induced reactions of dehydrogenation, decarboxylation and deamination of ch... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=984307 Mon, 01 Oct 2007 04:00:00 +0100 984307 http://www.medworm.com/index.php?rid=984306&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17594532%26dopt%3DAbstract Authors: De Lucrezia D, Anella F, Chiarabelli C The discovery of catalytic RNA has revolutionised modern molecular biology and bears important implications for the origin of Life research. Catalytic RNA, in particular self-replicating RNA, prompted the hypothesis of an early "RNA world" where RNA molecules played all major roles such information storage and catalysis. The actual role of RNA as primary actor in the origin of life has been under debate for a long time, with a particular emphasis on possible pathways to the prebiotic synthesis of mononucleotides; their polymerization and the possibility of spontaneous emergence of catalytic RNAs synthesised under plausible prebiotic conditions. However, little emphasis has been put on the chemical reality of an RNA world; in particular co... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=984306 Mon, 01 Oct 2007 04:00:00 +0100 984306 http://www.medworm.com/index.php?rid=984305&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17597419%26dopt%3DAbstract Authors: Islas S, Hernández-Morales R, Lazcano A Inventories of the gene content of the last common ancestor (LCA), i.e., the cenancestor, include sequences that may have undergone horizontal transfer events, as well as sequences that have originated in different pre-cenancestral epochs. However, the universal distribution of highly conserved genes involved in RNA metabolism provide insights into early stages of cell evolution during which RNA played a much more conspicuous biological role, and is consistent with the hypothesis that extant living systems were preceded by an RNA/protein world. Insights into the traits of primitive entities from which the LCA evolved may be derived from the analysis of paralogous gene families, including those formed by sequences that resulted from ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=984305 Mon, 01 Oct 2007 04:00:00 +0100 984305 http://www.medworm.com/index.php?rid=984304&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17597420%26dopt%3DAbstract Authors: Mavelli F, Ruiz-Mirazo K In this short paper we argue for the relevance and value of theoretical models in the field of origins of life, but also claim that both theoreticians and experimentalists should make an effort to come together and interact more closely to obtain more fruitful and significant results. As an example, we present our own modeling approach to protocell dynamics, including some simulation results, to show that it is possible to develop computational tools that start bridging that traditional gap between theory and experiments. PMID: 17597420 [PubMed - in process] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=984304 Mon, 01 Oct 2007 04:00:00 +0100 984304 http://www.medworm.com/index.php?rid=984303&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17602310%26dopt%3DAbstract Authors: Stano P, Luisi PL PMID: 17602310 [PubMed - in process] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=984303 Mon, 01 Oct 2007 04:00:00 +0100 984303 http://www.medworm.com/index.php?rid=984302&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17602311%26dopt%3DAbstract Question 1: Commentary Referring to the Statement "The Origin of Life can be Traced Back to the Origin of Kinetic Control" and the Question "Do You Agree with this Statement; and How Would You Envisage the Prebiotic Evolutionary Bridge Between Thermodynamic and Kinetic Control?" Stated in Section 1.1. Orig Life Evol Biosph. 2007 Oct;37(4-5):309-14 Authors: Eschenmoser A The paper summarizes thoughts induced by some of the programmatic questions Pier Luigi Luisi posed for discussion at the Erice workshop. PMID: 17602311 [PubMed - in process] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=984302 Mon, 01 Oct 2007 04:00:00 +0100 984302 http://www.medworm.com/index.php?rid=984301&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17610044%26dopt%3DAbstract Authors: Avetisov V These short remarks about the origin of biological homochirality are focused on the questions related to the origin and selection of homochiral polymers and the broken mirror symmetry. They are important questions, but still equally unanswered, since the answers, I believe, closely relate to the evolutionary paradigm we accept. The prebiotic evolutionary paradigm, as it seems to me, should be based on idea of "progressive evolution of structural and functional complexity," and the typical combinatorial constraints similar to the error catastrophe, which come into being due to the very complexity, must not appear here. PMID: 17610044 [PubMed - in process] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=984301 Mon, 01 Oct 2007 04:00:00 +0100 984301 http://www.medworm.com/index.php?rid=984300&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17610045%26dopt%3DAbstract Authors: Stano P In this short article I discuss the relevance of two aspects of vesicle reactivity that are germane to understand the role of compartments in the origin of early cells. Studies of vesicle self-reproduction indicate that simple vesicles can grow and divide, maintaining inside most of their content and giving rise to a simple autopoietic system. New aspects of vesicle reactivity are also introduced, such as selection and competition processes within vesicle populations, emphasizing the concepts of vesicle diversity, inter-vesicles and vesicles-environment interactions, intended as synthetic analogs of primitive 'ecological' processes. PMID: 17610045 [PubMed - in process] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=984300 Mon, 01 Oct 2007 04:00:00 +0100 984300 http://www.medworm.com/index.php?rid=984299&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17610046%26dopt%3DAbstract Authors: Tamulis A, Tamulis V Natural and artificial living cells and their substructures are self-assembling, due to electron correlation interactions among biological and water molecules, which lead to attractive dispersion forces and hydrogen bonds. Dispersion forces are weak intermolecular forces that arise from the attractive force between quantum multipoles. A hydrogen bond is a special type of quantum attractive interaction that exists between an electronegative atom and a hydrogen atom bonded to another electronegative atom; and this hydrogen atom exist in two quantum states. The best method to simulate these dispersion forces and hydrogen bonds is to perform quantum mechanical non-local density functional potential calculations of artificial minimal living cells consisting of ... Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=984299 Mon, 01 Oct 2007 04:00:00 +0100 984299 http://www.medworm.com/index.php?rid=984298&cid=s_36646_67_f&fid=36646&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D17610047%26dopt%3DAbstract Authors: Pizzarello S Astrobiological studies of abiotic organic chemistry, such as it is observed in interstellar molecular clouds or found in comets and meteorites, offer a glimpse of the chemical evolution that preceded the onset of life. They also allow to evaluate the possibility that the molecules produced through the long cosmic history of the biogenic elements contributed to the early Earth organic pool and facilitated prebiotic molecular evolution. PMID: 17610047 [PubMed - in process] (Source: Origins of Life and Evolution of the Biosphere) Origins of Life and Evolution of the Biosphere journals http://www.medworm.com/rss/comments.php?id=984298 Mon, 01 Oct 2007 04:00:00 +0100 984298