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 'PMC Biophysics' source. Thu, 18 Mar 2010 16:35:13 +0100 http://www.medworm.com/index.php?rid=3377949&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F3%2F7 This report deals with actin waves that are spontaneously generated on the planar, substrate-attached surface of Dictyostelium cells. These waves have the following characteristics. (1) They are circular structures of varying shape, capable of changing the direction of propagation. (2) The waves propagate by treadmilling with a recovery of actin incorporation after photobleaching of less than 10 seconds. (3) The waves are associated with actin-binding proteins in an ordered 3-dimensional organization: with myosin-IB at the front and close to the membrane, the Arp2/3 complex throughout the wave, and coronin at the cytoplasmic face and back of the wave. Coronin is a marker of disassembling actin structures. (4) The waves separate two areas of the cell cortex that differ in actin structure an... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=3377949 Thu, 18 Mar 2010 00:00:00 +0100 3377949 http://www.medworm.com/index.php?rid=3346190&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F3%2F6 Polymerization of actin into filaments can push membranes forming extensions like filopodia or lamellipodia, which are important during processes such as cell motility and phagocytosis. Similarly, small organelles or pathogens can be moved by actin polymerization. Such actin filaments can be arranged in different patterns and are usually hundreds of nanometers in length as revealed by various electron microscopy approaches. Much shorter actin filaments are involved in the motility of apicomplexan parasites. However, these short filaments have to date not been visualized in intact cells. Here, we investigated Plasmodium sporozoites, the motile forms of the malaria parasite that are transmitted by the mosquito, using cryogenic electron tomography. We detected filopodia-like extensions of the... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=3346190 Fri, 05 Mar 2010 00:00:00 +0100 3346190 http://www.medworm.com/index.php?rid=3334869&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F3%2F2 Polymerization of actin into filaments can push membranes forming extensions like filopodia or lamellipodia, which are important during processes such as cell motility and phagocytosis. Similarly, small organelles or pathogens can be moved by actin polymerization. Such actin filaments can be arranged in different patterns and are usually hundreds of nanometers in length as revealed by various electron microscopy approaches. Much shorter actin filaments are involved in the motility of apicomplexan parasites. However, these short filaments have to date not been visualized in intact cells. Here, we investigated Plasmodium sporozoites, the motile forms of the malaria parasite that are transmitted by the mosquito, using cryogenic electron tomography. We detected filopodia-like extensions of the... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=3334869 Fri, 05 Mar 2010 00:00:00 +0100 3334869 http://www.medworm.com/index.php?rid=3334868&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F3%2F3 In this study we determined PML NB assembly dynamics by live cell imaging, combined with mathematical modeling. For the first time, dynamics of PML body formation were measured in cells lacking endogenous PML. We show that all six human nuclear PML isoforms are able to form nuclear bodies in PML negative cells. All isoforms exhibit individual exchange rates at NBs in PML positive cells but PML I, II, III and IV are static at nuclear bodies in PML negative cells, suggesting that these isoforms require additional protein partners for efficient exchange. PML V turns over at PML NBs very slowly supporting the idea of a structural function for this isoform. We also demonstrate that SUMOylation of PML at Lysine positions K160 and/or K490 are required for nuclear body formation in vivo. We propos... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=3334868 Fri, 05 Mar 2010 00:00:00 +0100 3334868 http://www.medworm.com/index.php?rid=3334867&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F3%2F4 This study demonstrates that two-color STED microscopy in conjunction with quantitative colocalization analysis is a powerful tool to study the complex distribution of membrane proteins in organelles such as mitochondria.PACS: 87.16.Tb, 87.85.Rs (Source: PMC Biophysics) PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=3334867 Fri, 05 Mar 2010 00:00:00 +0100 3334867 http://www.medworm.com/index.php?rid=3334866&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F3%2F5 Conclusion: FRET measurements do not only allow following the assembly of the HIF-1 complex under hypoxic conditions but can also provide important information about the process of O2-sensing and its localisation within a cell.MCS codes: 92C30, 92C05, 92C40 (Source: PMC Biophysics) PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=3334866 Fri, 05 Mar 2010 00:00:00 +0100 3334866 http://www.medworm.com/index.php?rid=3197347&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F3%2F2 TRPM7/ChaK1 is a recently discovered atypical protein kinase that has been suggested to selectively phosphorylate the substrate residues located in alpha-helices. However, the actual structure of kinase-substrate complex has not been determined experimentally and the recognition mechanism remains unknown. In this work we explored possible kinase-substrate binding modes and the likelihood of an alpha-helix docking interaction, within a kinase active site, using molecular modeling. Specifically kinase ChaK1 and its two peptide substrates were examined; one was an 11-residue segment from the N-terminal domain of annexin-1, a putative endogenous substrate for ChaK1, and the other was an engineered 16-mer peptide substrate determined via peptide library screening. Simulated annealing (SA), repl... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=3197347 Thu, 21 Jan 2010 00:00:00 +0100 3197347 http://www.medworm.com/index.php?rid=3185022&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F3%2F1 The Debye-Huckel limiting law (DHL) has often been used to estimate rate constants of diffusion-controlled reactions under different ionic strengths. Two main approximations are adopted in DHL: one is that the solution of the linearized Poisson-Boltzmann equation for a spherical cavity is used to estimate the excess electrostatic free energy of a solution; the other is that details of electrostatic interactions of the solutes are neglected. This makes DHL applicable only at low ionic strengths and dilute solutions (very low substrate/solute concentrations). We show in this work that through numerical solution of the Poisson-Nernst-Planck equations, diffusion-reaction processes can be studied at a variety of conditions including realistically concentrated solutions, high ionic strength, and... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=3185022 Mon, 18 Jan 2010 00:00:00 +0100 3185022 http://www.medworm.com/index.php?rid=3108178&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F2%2F11 Ca2+ binding proteins are essential for regulating the role of Ca2+ in cell signaling and maintaining Ca2+ homeostasis. Negatively charged residues such as Asp and Glu are often found in Ca2+ binding proteins and are known to influence Ca2+ binding affinity and protein stability. In this paper, we report a systematic investigation of the role of local charge number and type of coordination residues in Ca2+ binding and protein stability using de novo designed Ca2+ binding proteins. The approach of de novo design was chosen to avoid the complications of cooperative binding and Ca2+-induced conformational change associated with natural proteins. We show that when the number of negatively charged coordination residues increased from 2 to 5 in a relatively restricted Ca2+-binding site, Ca2+ bin... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=3108178 Mon, 21 Dec 2009 00:00:00 +0100 3108178 http://www.medworm.com/index.php?rid=2999215&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F2%2F10 Intrinsic noise is a common phenomenon in biochemical reaction networks and may affect the occurence and amplitude of sustained oscillations in the states of the network. To evaluate properties of such oscillations in the time domain, it is usually required to conduct long-term stochastic simulations, using for example the Gillespie algorithm. In this paper, we present a new method to compute the amplitude distribution of the oscillations without the need for long-term stochastic simulations. By the derivation of the method, we also gain insight into the structural features underlying the stochastic oscillations. The method is applicable to a wide class of non-linear stochastic differential equations that exhibit stochastic oscillations. The application is exemplified for the MAPK cascade,... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2999215 Tue, 17 Nov 2009 00:00:00 +0100 2999215 http://www.medworm.com/index.php?rid=2980763&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F2%2F9 Nanosecond, megavolt-per-meter electric pulses cause permeabilization of cells to small molecules, programmed cell death (apoptosis) in tumor cells, and are under evaluation as a treatment for skin cancer. We use nanoelectroporation and fluorescence imaging to construct two-dimensional maps of the electric field associated with delivery of 15 ns, 10 kV pulses to monolayers of the human prostate cancer cell line PC3 from three different electrode configurations: single-needle, five-needle, and flat-cut coaxial cable. Influx of the normally impermeant fluorescent dye YO-PRO-1 serves as a sensitive indicator of membrane permeabilization. The level of fluorescence emission after pulse exposure is proportional to the applied electric field strength. Spatial electric field distributions were com... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2980763 Wed, 11 Nov 2009 00:00:00 +0100 2980763 http://www.medworm.com/index.php?rid=2915806&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F2%2F8 FtsZ is a GTPase that assembles at midcell into a dynamic ring that constricts the membrane to induce cell division in the majority of bacteria,in many archea and several organelles. In vitro, FtsZ polymerizes in a GTP-dependent manner forming a variety of filamentous flexible structures. Based on data derived from the measurement of the in vitro polymerization of Escherichia coli FtsZ cell division protein we have formulated a model in which the fine balance between curvature, flexibility and lateral interactions accounts for structural and dynamic properties of the FtsZ polymers observed with AFM. The experimental results have been used by the model to calibrate the interaction energies and the values obtained indicate that the filaments are very plastic. The extension of the model to ex... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2915806 Wed, 21 Oct 2009 23:00:00 +0100 2915806 http://www.medworm.com/index.php?rid=2729744&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F2%2F7 This study tested the hypothesis that microvesicle release depends on microscopic membrane physical properties such as lipid order, fluidity, and composition. Membrane properties were manipulated by varying the experimental temperature, membrane cholesterol content, and the activity of the trans-membrane phospholipid transporter, scramblase. Microvesicle release was enhanced by increasing the experimental temperature. Reduction in membrane cholesterol content by treatment with methyl-beta-cyclodextrin also facilitated vesicle shedding. Inhibition of scramblase with R5421 impaired vesicle release. These data were interpreted in the context of membrane characteristics assessed previously by fluorescence spectroscopy with environment-sensitive probes such as laurdan, diphenylhexatriene, and m... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2729744 Sun, 23 Aug 2009 23:00:00 +0100 2729744 http://www.medworm.com/index.php?rid=2597786&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F2%2F6 We present a macroscopic theory of electroencephalogram (EEG) dynamics based on the laws of motion that govern atomic and molecular motion. The theory is an application of Zwanzig-Mori projection operators. The result is a simple equation of motion that has the form of a generalized Langevin equation (GLE), which requires knowledge only of macroscopic properties. The macroscopic properties can be extracted from experimental data by one of two possible variational principles. These variational principles are our principal contribution to the formalism. Potential applications are discussed, including applications to the theory of critical phenomena in the brain, Granger causality and Kalman filters.PACS codes: 87.19.lj (Source: PMC Biophysics) PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2597786 Sun, 12 Jul 2009 23:00:00 +0100 2597786 http://www.medworm.com/index.php?rid=2590994&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2Fcontent%2F2%2F1%2F5 In this study, the stabilities of all core domain missense mutations are predicted and are used to infer their likely inactivation mechanisms. Overall, 47.0% non-PRO/GLY mutants are stable (ΔΔG < 1.0 kT) and 36.3% mutants are unstable (ΔΔG > 3.0 kT), 12.2% mutants are with 1.0 kT < ΔΔG < 3.0 kT. Only 4.5% mutants are with no conclusive predictions. Certain types of either stable or unstable mutations are found not to depend on their local structures. Y, I, C, V, F and W (W, R and F) are the most common residues before (after) mutation in unstable mutants. Q, N, K, D, A, S and T (I, T, L and V) are the most common residues before (after) mutation in stable mutants. The stability correlations with sequence, structure, and molecular contacts are also analyzed. No direct correlation betw... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2590994 Thu, 25 Jun 2009 23:00:00 +0100 2590994 http://www.medworm.com/index.php?rid=2527293&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F2%2F5 In this study, the stabilities of all core domain missense mutations are predicted and are used to infer their likely inactivation mechanisms. Overall, 47.0% non-PRO/GLY mutants are stable (DeltaDeltaG < 1.0kT) and 36.3% mutants are unstable (DeltaDeltaG > 3.0kT), 12.2% mutants are with 1.0kT < DeltaDeltaG < 3.0kT. Only 4.5% mutants are with no conclusive predictions. Certain types of either stable or unstable mutations are found not to depend on their local structures. Y, I, C, V, F and W (W, R and F) are the most common residues before (after) mutation in unstable mutants. Q, N, K, D, A, S and T (I, T, L and V) are the most common residues before (after) mutation in stable mutants. The stability correlations with sequence, structure, and molecular contacts are also analyzed. No direct co... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2527293 Thu, 25 Jun 2009 23:00:00 +0100 2527293 http://www.medworm.com/index.php?rid=2439971&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F2%2F4 The acidic C-terminal peptides from Trypanosoma cruzi ribosomal P proteins are the major target of the antibody response in patients suffering Chagas's chronic heart disease. It has been proposed that the disease is triggered by the cross-reaction of these antibodies with the second extra cellular loop of the beta1-adrenoreceptor, brought about by the molecular mimicry between the acidic C-terminal peptides and the receptor's loop. To improve the understanding of the structural basis of the autoimmune response against heart receptors, the 3-dimensional structure of the C-terminal peptides of Trypanosoma cruzi ribosomal proteins P0 (EDDDDDFGMGALF) and P2beta (EEEDDDMGFGLFD) were solved using the Electrostaticaly Driven MonteCarlo method. Their structures were compared with the second extra-... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2439971 Wed, 27 May 2009 04:00:00 +0100 2439971 http://www.medworm.com/index.php?rid=2572775&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F2%2F4 The acidic C-terminal peptides from Trypanosoma cruzi ribosomal P proteins are the major target of the antibody response in patients suffering Chagas chronic heart disease. It has been proposed that the disease is triggered by the cross-reaction of these antibodies with the second extra cellular loop of the β1-adrenoreceptor, brought about by the molecular mimicry between the acidic C-terminal peptides and the receptor's loop. To improve the understanding of the structural basis of the autoimmune response against heart receptors, the 3-dimensional structure of the C-terminal peptides of Trypanosoma cruzi ribosomal proteins P0 (EDDDDDFGMGALF) and P2β (EEEDDDMGFGLFD) were solved using the Electrostaticaly Driven MonteCarlo method. Their structures were compared with the second extra-cellul... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2572775 Tue, 26 May 2009 23:00:00 +0100 2572775 http://www.medworm.com/index.php?rid=2340745&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F2%2F3 Lipids, the building blocks of cells, common to every living organisms, have the propensity to self-assemble into well-defined structures over short and long-range spatial scales. The driving forces have their roots mainly in the hydrophobic effect and electrostatic interactions. Membranes in lamellar phase are ubiquitous in cellular compartments and can phase-separate upon mixing lipids in different liquid-crystalline states. Hexagonal phases and especially cubic phases can be synthesized and observed in vivo as well. Membrane often closes up into a vesicle whose shape is determined by the interplay of curvature, area difference elasticity and line tension energies, and can adopt the form of a sphere, a tube, a prolate, a starfish and many more. Complexes made of lipids and polyelectrolyt... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2340745 Fri, 17 Apr 2009 04:00:00 +0100 2340745 http://www.medworm.com/index.php?rid=2327995&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F2%2F2 We describe and test an implicit solvent all-atom potential for simulations of protein folding and aggregation. The potential is developed through studies of structural and thermodynamic properties of 17 peptides with diverse secondary structure. Results obtained using the final form of the potential are presented for all these peptides. The same model, with unchanged parameters, is furthermore applied to a heterodimeric coiled-coil system, a mixed alpha/beta protein and a three-helix-bundle protein, with very good results. The computational efficiency of the potential makes it possible to investigate the free-energy landscape of these 49-67-residue systems with high statistical accuracy, using only modest computational resources by today's standards. PACS Codes: 87.14.E-, 87.15.A-, 87.15.... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2327995 Wed, 08 Apr 2009 04:00:00 +0100 2327995 http://www.medworm.com/index.php?rid=2164557&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F2%2F1 Correlation of lipid disorder with membrane protein dynamics has been studied with infrared spectroscopy, by combining data characterizing lipid phase, protein structure and, via hydrogen-deuterium (H/D) exchange, protein dynamics. The key element was a new measuring scheme, by which the combined effects of time and temperature on the H/D exchange could be separated. Cyanobacterial and plant thylakoid membranes, mammalian mitochondria membranes, and for comparison, lysozyme were investigated. In dissolved lysozyme, as a function of temperature, H/D exchange involved only reversible movements (the secondary structure did not change considerably); heat-denaturing was a separate event at much higher temperature. Around the low-temperature functioning limit of the biomembranes, lipids affected... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2164557 Fri, 06 Feb 2009 05:00:00 +0100 2164557 http://www.medworm.com/index.php?rid=2076893&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F1%2F7 Finding the global probabilistic nature of a non-equilibrium circadian clock is essential for addressing important issues of robustness and function. We have uncovered the underlying potential energy landscape of a simple cyanobacteria biochemical network, and the corresponding flux which is the driving force for the oscillation. We found that the underlying potential landscape for the oscillation in the presence of small statistical fluctuations is like an explicit ring valley or doughnut shape in the three dimensional protein concentration space. We found that the barrier height separating the oscillation ring and other area is a quantitative measure of the oscillation robustness and decreases when the fluctuations increase. We also found that the entropy production rate characterizing t... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2076893 Tue, 30 Dec 2008 05:00:00 +0100 2076893 http://www.medworm.com/index.php?rid=2048742&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F1%2F6 Analysis of fluorescent spectra from complex biological systems containing various fluorescent probes with overlapping emission bands is a challenging task. Valuable information can be extracted from the full spectra, however, by using multivariate analysis (MA) of measurements at different wavelengths. We applied MA to spectral data of purified Torpedo nicotinic acetylcholine receptor (AChR) protein reconstituted into liposomes made up of dioleoylphosphatidic acid (DOPA) and dioleoylphosphatidylcholine (DOPC) doped with two extrinsic fluorescent probes (NBD-cholesterol/pyrene-PC). Forster resonance energy transfer (FRET) was observed between the protein and pyrene-PC and between pyrene-PC and NBD-cholesterol, leading to overlapping emission bands. Partial least squares analysis was applie... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2048742 Thu, 18 Dec 2008 05:00:00 +0100 2048742 http://www.medworm.com/index.php?rid=2000154&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F1%2F5 We discuss a stochastic approach for reconstructing the native structures of proteins from the knowledge of the "effective connectivity'', which is a one-dimensional structural profile constructed as a linear combination of the eigenvectors of the contact map of the target structure. The structural profile is used to bias a search of the conformational space towards the target structure in a Monte Carlo scheme operating on a C_alpha-chain of uniform, finite thickness. Structure information thus enters the folding dynamics via the effective connectivity, but the interaction is not restricted to pairs of amino acids that form native contacts, resulting in a free energy landscape which does not rely on the assumption of minimal frustration. Moreover, effective connectivity vectors can be pred... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2000154 Wed, 26 Nov 2008 05:00:00 +0100 2000154 http://www.medworm.com/index.php?rid=2000158&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F1%2F1 Welcome to PMC Biophysics, an international, peer-reviewed, open access journal devoted to biological physics in all its myriad forms. The journal has been launched in response to two significant trends in publishing and research. (Source: PMC Biophysics) PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2000158 Wed, 05 Nov 2008 05:00:00 +0100 2000158 http://www.medworm.com/index.php?rid=2000157&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F1%2F2 Calculations of electrostatic properties of protein-protein complexes are usually done within framework of a model with a certain set of parameters. In this paper we present a comprehensive statistical analysis of the sensitivity of the electrostatic component of binding free energy (DDGel) with respect with different force fields (Charmm, Amber, and OPLS), different values of the internal dielectric constant, and different presentations of molecular surface (different values of the probe radius). The study was done using the largest so far set of entries comprising 260 hetero and 2148 homo protein-protein complexes extracted from a previously developed database of protein complexes (ProtCom). To test the sensitivity of the energy calculations with respect to the structural details, all st... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2000157 Wed, 05 Nov 2008 05:00:00 +0100 2000157 http://www.medworm.com/index.php?rid=2000156&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F1%2F3 The environmental impact of metal complexes such as organotin(IV) compounds is of increasing concern. Genotoxic effects of organotin(IV) compounds (0.01 microg/ml, 0.1 microg/ml or 1.0 microg/ml) were measured using the alkaline single-cell gel electrophoresis (comet) assay to measure DNA single-strand breaks (SSBs) and the cytokinesis-block micronucleus (CBMN) assay to determine micronucleus formation. Biochemical-cell signatures were also ascertained using attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. In the comet assay, organotin(IV) carboxylates induced significantly-elevated levels of DNA SSBs. Elevated micronucleus-forming activities were also observed. Following interrogation using ATR-FTIR spectroscopy, infrared spectra in the biomolecular range (9... PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2000156 Wed, 05 Nov 2008 05:00:00 +0100 2000156 http://www.medworm.com/index.php?rid=2000155&cid=s_38191_75_f&fid=38191&url=http%3A%2F%2Fwww.physmathcentral.com%2F1757-5036%2F1%2F4 A purely electrical sensing scheme is presented that determines the concentration of macromolecules in solution by measuring the capacitance between planar microelectrodes. Concentrations of DNA in the ng/mL range have been used in samples of 1 microL volume. The method has been applied to the characterisation of the dielectrophoretic response of DNA without the need for any chemical modifications. The influence of electrical parameters like duty cycle, voltage and frequency has been investigated. The results are in good agreement with data from dielectrophoretic studies on fluorescently labelled DNA. Extension of the method down to the single molecule level appears feasible. PACS: 87.50.ch, 87.80.Fe, 87.85.fK (Source: PMC Biophysics) PMC Biophysics journals http://www.medworm.com/rss/comments.php?id=2000155 Wed, 05 Nov 2008 05:00:00 +0100 2000155