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 'Journal of Biophysics' source. Fri, 19 Mar 2010 17:32:57 +0100 http://www.medworm.com/index.php?rid=3254011&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2Fjournals%2Fjbp%2F2009%2F819635.html Differential scanning calorimetry (DSC) has been used to estimate the effect of disc disease on the collagen helix-coil transition and morphology for tissue extracted from patients during surgical operation. Forty discs were obtained from patients with degenerative disc disease undergoing surgery for low back pain. The patients were in the age between 20 and 70 years old. The specimens were kept wet during DSC experiment. The data allow the comparison between thermal stability of collagen tissue from healthy patients and from patients suffering from disc disease. In the paper the comparison between thermal helix-coil transition for collagen fibers from patients suffering from disc disease and collagen fibers from healthy organisms has been discussed. The heating rate has an influence on th... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=3254011 Tue, 09 Feb 2010 16:34:54 +0100 3254011 http://www.medworm.com/index.php?rid=3239124&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2Fjournals%2Fjbp%2F2009%2F210485.html A number of proteins with intrinsically disordered (ID) regions/domains are reported to be found disproportionately higher in transcription factors. Available evidences suggest that presence of ID region/domain within a transcription factor plays an important role in its biological functions. These ID sequences provide large flexible surfaces that can allow them to make more efficient physical and functional interactions with their target partners. Since transcription factors regulate expression of target genes by interacting with specific coregulatory proteins, these ID regions/domains can be used as a platform for such large macromolecular interactions, and may represent a mechanism for regulation of cellular processes. The precise structural basis for the function of these ID regions/do... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=3239124 Thu, 04 Feb 2010 16:38:55 +0100 3239124 http://www.medworm.com/index.php?rid=2902729&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2Fjournals%2Fjbp%2F2009%2F380976.html A quantitative frequency-domain model of induction-based magnetoreception is presented for elasmobranch fishes. We show that orientation with respect to the geomagnetic field can be determined by synchronous detection of electrosensory signals at harmonics of the vestibular frequency. The sensitivity required for this compass-sense mechanism is shown to be less than that known from behavioral experiments. Recent attached-magnet experiments have called into doubt the induction-based mechanism for magnetoreception. We show that the use of attached magnets would interfere with an induction-based mechanism unless relative movement between the electrosensory system and the attached magnet is less than 100 μm. This suggests that further experiments may be required to eliminate indu... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=2902729 Sun, 18 Oct 2009 14:42:39 +0100 2902729 http://www.medworm.com/index.php?rid=2886090&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2Fjournals%2Fjbp%2F2009%2F380967.html Tropomyosin (Tm) consists of 7 quasiequivalent repeats known as “periods,” and its specific function may be associated with these periods. To test the hypothesis that either period 2 or 3 promotes force generation by inducing a positive allosteric effect on actin, we reconstituted the thin filament with mutant Tm in which either period 2 (Δ2Tm) or period 3 (Δ3Tm) was deleted. We then studied: isometric tension, stiffness, 6 kinetic constants, and the pCa-tension relationship. N-terminal acetylation of Tm did not cause any differences. The isometric tension in Δ2Tm remained unchanged, and was reduced to ~60% in Δ3Tm. Although the kinetic constants underwent small changes, the occupancy of strongly attached cross-bridges was not much different... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=2886090 Tue, 13 Oct 2009 15:10:20 +0100 2886090 http://www.medworm.com/index.php?rid=2550152&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2Fjournals%2Fjbp%2F2009%2F434038.html The crystal structure of a putative dipeptidase (Phdpd) from Pyrococcus horikoshii OT3 was solved using X-ray data at 2.4 Å resolution. The protein is folded into two distinct entities. The N-terminal domain consists of the general topology of the α/β fold, and the C-terminal domain consists of five long mixed strands, four helices, and two 310 helices. The structure of Phdpd is quite similar to reported structures of prolidases from P. furiosus (Zn-Pfprol) and P. horikoshii (Zn-Phdpd), where Zn ions are observed in the active site resulting in an inactive form. However, Phdpd did not contain metals in the crystal structure and showed prolidase activity in the absence of additional Co ions, whereas the specific activities increased by 5 times in the presence of a ... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=2550152 Sun, 28 Jun 2009 16:13:56 +0100 2550152 http://www.medworm.com/index.php?rid=2468508&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2Fjournals%2Fjbp%2F2008%2F602870.html Since thermal gradients are almost everywhere, thermosensation could represent one of the oldest sensory transduction processes that evolved in organisms. There are many examples of temperature changes affecting the physiology of living cells. Almost all classes of biological macromolecules in a cell (nucleic acids, lipids, proteins) can present a target of the temperature-related stimuli. This review discusses some features of different classes of temperature-sensing molecules as well as molecular and biological processes that involve thermosensation. Biochemical, structural, and thermodynamic approaches are applied in the paper to organize the existing knowledge on molecular mechanisms of thermosensation. Special attention is paid to the fact that thermosensitive function cannot be assig... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=2468508 Wed, 10 Jun 2009 05:18:46 +0100 2468508 http://www.medworm.com/index.php?rid=2468507&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2Fjournals%2Fjbp%2F2008%2F474205.html The targets for tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), and selective norepinephrine reuptake inhibitors (SNRIs) are known to be the serotonin and norepinephrine transport (reuptake) proteins which are embedded in presynaptic nerve terminals and function to bring these neurotransmitters from the synaptic cleft back into the presynaptic neuron. Using a combination of intrinsic and extrinsic fluorescence quenching, Stern-Volmer analysis, and protease protection assays, we have shown that therapeutics from each of these three classes of antidepressants bind to the extracellular S1S2 domain of the NR1-1b subunit of the NMDA receptor. These results are in agreement with recent work from our lab demonstrating the interaction of antidepressants with the ... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=2468507 Wed, 10 Jun 2009 05:18:46 +0100 2468507 http://www.medworm.com/index.php?rid=2468506&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2Fjournals%2Fjbp%2F2008%2F420963.html The purpose of this study was to investigate the time course of the volume-regulatory response and intracellular sodium concentration ([Na+]i) in the principal cells of rat kidney outer medulla collecting duct (OMCD) epithelia during acute swelling in hypotonic medium. Hypotonic shock was created by PBS diluted with 50% of water. Changes in cell volume were measured with calcein quenching method. Intracellular sodium concentration was studied with fluorescence dye Sodium Green. Principal cells of microdissected OMCD fragments swelled very fast. The characteristic time of swelling (τ1) was 0.65±0.05 seconds, and the volume increased more than 60% (92.9±5.6 and 151.3±9.8 μm3 control and peak volumes correspondently, P<.01). Afte... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=2468506 Wed, 10 Jun 2009 05:18:46 +0100 2468506 http://www.medworm.com/index.php?rid=2468505&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2Fjournals%2Fjbp%2F2008%2F267912.html Chemo- and phototaxis systems in bacteria and archaea serve as models for more complex signal transduction mechanisms in higher eukaryotes. Previous studies of the cytoplasmic fragment of the phototaxis transducer (pHtrII-cyt) from the halophilic archaeon Natronomonas pharaonis showed that it takes the shape of a monomeric or dimeric rod under low or high salt conditions, respectively. CD spectra revealed only approximately 24% helical structure, even in 4 M KCl, leaving it an open question how the rod-like shape is achieved. Here, we conducted CD, FTIR, and NMR spectroscopic studies under different conditions to address this question. We provide evidence that pHtrII-cyt is highly dynamic with strong helical propensity, which allows it to change from monomeric to dimeric helical co... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=2468505 Wed, 10 Jun 2009 05:18:46 +0100 2468505 http://www.medworm.com/index.php?rid=2468504&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2Fjournals%2Fjbp%2F2008%2F602639.html NADPH oxidase (NOX2) is a multisubunit membrane-bound enzyme complex that, upon assembly in activated cells, catalyses the reduction of free oxygen to its superoxide anion, which further leads to reactive oxygen species (ROS) that are toxic to invading pathogens, for example, the fungus Aspergillus fumigatus. Polymorphonuclear cells (PMNs) employ both nonoxidative and oxidative mechanisms to clear this fungus from the lung. The oxidative mechanisms mainly depend on the proper assembly and function of NOX2. We identified for the first time the NAD(P)H-dependent enzymes involved in such oxidative mechanisms by means of biexponential NAD(P)H-fluorescence lifetime imaging (FLIM). A specific fluorescence lifetime of 3670±140 picoseconds as compared to 1870 picoseconds for NAD(P)H bound t... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=2468504 Wed, 10 Jun 2009 05:18:46 +0100 2468504 http://www.medworm.com/index.php?rid=2468503&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2Fjournals%2Fjbp%2F2008%2F654672.html The species-area relationship is one of the central generalizations in ecology; however, its origin has remained a puzzle. Since ecosystems are understood as energy transduction systems, the regularities in species richness are considered to result from ubiquitous imperatives in energy transduction. From a thermodynamic point of view, organisms are transduction mechanisms that distribute an influx of energy down along the steepest gradients to the ecosystem's diverse repositories of chemical energy, that is, populations of species. Transduction machineries, that is, ecosystems assembled from numerous species, may emerge and evolve toward high efficiency on large areas that hold more matter than small ones. This results in the well-known logistic-like relationship between the area and t... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=2468503 Wed, 10 Jun 2009 05:18:46 +0100 2468503 http://www.medworm.com/index.php?rid=2468502&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2Fjournals%2Fjbp%2F2008%2F183516.html The malignancy of cancer disease depends on the ability of the primary tumor to metastasize to distant organs. The process of the metastasis formation has largely been analyzed, but still main pathways regarding the extravasation step at the end of the metastasis formation process are controversially discussed. An agreement has been reached about the importance of the endothelium to promote metastasis formation either by enhancing the growth of the primary tumor or by homing (targeting) the tumor cells to blood or lymph vessels. The mechanical properties of the invading tumor cells become the focus of several studies, but the endothelial cell mechanical properties are still elusive. This paper describes the different roles of the endothelium in the process of metastasis formation and focus... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=2468502 Wed, 10 Jun 2009 05:18:46 +0100 2468502 http://www.medworm.com/index.php?rid=2242159&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2FGetArticle.aspx%3Fdoi%3D10.1155%2F2008%2F183516 The malignancy of cancer disease depends on the ability of the primary tumor to metastasize to distant organs. The process of the metastasis formation has largely been analyzed, but still main pathways regarding the extravasation step at the end of the metastasis formation process are controversially discussed. An agreement has been reached about the importance of the endothelium to promote metastasis formation either by enhancing the growth of the primary tumor or by homing (targeting) the tumor cells to blood or lymph vessels. The mechanical properties of the invading tumor cells become the focus of several studies, but the endothelial cell mechanical properties are still elusive. This paper describes the different roles of the endothelium in the process of metastasis formation and focus... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=2242159 Sat, 07 Mar 2009 15:12:01 +0100 2242159 http://www.medworm.com/index.php?rid=2028827&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2FGetArticle.aspx%3Fdoi%3D10.1155%2F2008%2F654672 The species-area relationship is one of the central generalizations in ecology; however, its origin has remained a puzzle. Since ecosystems are understood as energy transduction systems, the regularities in species richness are considered to result from ubiquitous imperatives in energy transduction. From a thermodynamic point of view, organisms are transduction mechanisms that distribute an influx of energy down along the steepest gradients to the ecosystem's diverse repositories of chemical energy, that is, populations of species. Transduction machineries, that is, ecosystems assembled from numerous species, may emerge and evolve toward high efficiency on large areas that hold more matter than small ones. This results in the well-known logistic-like relationship between the area and t... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=2028827 Thu, 11 Dec 2008 15:03:00 +0100 2028827 http://www.medworm.com/index.php?rid=1964735&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2FGetArticle.aspx%3Fdoi%3D10.1155%2F2008%2F602639 NADPH oxidase (NOX2) is a multisubunit membrane-bound enzyme complex that, upon assembly in activated cells, catalyses the reduction of free oxygen to its superoxide anion, which further leads to reactive oxygen species (ROS) that are toxic to invading pathogens, for example, the fungus Aspergillus fumigatus. Polymorphonuclear cells (PMNs) employ both nonoxidative and oxidative mechanisms to clear this fungus from the lung. The oxidative mechanisms mainly depend on the proper assembly and function of NOX2. We identified for the first time the NAD(P)H-dependent enzymes involved in such oxidative mechanisms by means of biexponential NAD(P)H-fluorescence lifetime imaging (FLIM). A specific fluorescence lifetime of 3670±140 picoseconds as compared to 1870 picoseconds for NAD(P)H bound t... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=1964735 Mon, 17 Nov 2008 11:40:16 +0100 1964735 http://www.medworm.com/index.php?rid=1880834&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2FGetArticle.aspx%3Fdoi%3D10.1155%2F2008%2F267912 Chemo- and phototaxis systems in bacteria and archaea serve as models for more complex signal transduction mechanisms in higher eukaryotes. Previous studies of the cytoplasmic fragment of the phototaxis transducer (pHtrII-cyt) from the halophilic archaeon Natronomonas pharaonis showed that it takes the shape of a monomeric or dimeric rod under low or high salt conditions, respectively. CD spectra revealed only approximately 24% helical structure, even in 4 M KCl, leaving it an open question how the rod-like shape is achieved. Here, we conducted CD, FTIR, and NMR spectroscopic studies under different conditions to address this question. We provide evidence that pHtrII-cyt is highly dynamic with strong helical propensity, which allows it to change from monomeric to dimeric helical co... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=1880834 Thu, 16 Oct 2008 15:16:42 +0100 1880834 http://www.medworm.com/index.php?rid=1657556&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2FGetArticle.aspx%3Fdoi%3D10.1155%2F2008%2F420963 The purpose of this study was to investigate the time course of the volume-regulatory response and intracellular sodium concentration ([Na+]i) in the principal cells of rat kidney outer medulla collecting duct (OMCD) epithelia during acute swelling in hypotonic medium. Hypotonic shock was created by PBS diluted with 50% of water. Changes in cell volume were measured with calcein quenching method. Intracellular sodium concentration was studied with fluorescence dye Sodium Green. Principal cells of microdissected OMCD fragments swelled very fast. The characteristic time of swelling (τ1) was 0.65±0.05 seconds, and the volume increased more than 60% (92.9±5.6 and 151.3±9.8 μm3 control and peak volumes correspondently, P<.01). Afte... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=1657556 Sun, 27 Jul 2008 12:42:43 +0100 1657556 http://www.medworm.com/index.php?rid=1494941&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2FGetArticle.aspx%3Fdoi%3D10.1155%2F2008%2F474205 The targets for tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), and selective norepinephrine reuptake inhibitors (SNRIs) are known to be the serotonin and norepinephrine transport (reuptake) proteins which are embedded in presynaptic nerve terminals and function to bring these neurotransmitters from the synaptic cleft back into the presynaptic neuron. Using a combination of intrinsic and extrinsic fluorescence quenching, Stern-Volmer analysis, and protease protection assays, we have shown that therapeutics from each of these three classes of antidepressants bind to the extracellular S1S2 domain of the NR1-1b subunit of the NMDA receptor. These results are in agreement with recent work from our lab demonstrating the interaction of antidepressants with the ... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=1494941 Thu, 05 Jun 2008 18:40:07 +0100 1494941 http://www.medworm.com/index.php?rid=1489772&cid=s_37039_75_f&fid=37039&url=http%3A%2F%2Fwww.hindawi.com%2FGetArticle.aspx%3Fdoi%3D10.1155%2F2008%2F602870 Since thermal gradients are almost everywhere, thermosensation could represent one of the oldest sensory transduction processes that evolved in organisms. There are many examples of temperature changes affecting the physiology of living cells. Almost all classes of biological macromolecules in a cell (nucleic acids, lipids, proteins) can present a target of the temperature-related stimuli. This review discusses some features of different classes of temperature-sensing molecules as well as molecular and biological processes that involve thermosensation. Biochemical, structural, and thermodynamic approaches are applied in the paper to organize the existing knowledge on molecular mechanisms of thermosensation. Special attention is paid to the fact that thermosensitive function cannot be assig... Journal of Biophysics journals http://www.medworm.com/rss/comments.php?id=1489772 Tue, 03 Jun 2008 22:24:49 +0100 1489772