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European Biophysics Journal: EBJ

Olivier Mignen, Bruno Constantin, Marie Potier-Cartereau, Aubin Penna, Mathieu Gautier, Maxime Guéguinou, Yves Renaudineau, Kenji F Shoji, Romain Félix, Elsa Bayet, Paul Buscaglia, Marjolaine Debant, Aurélie Chantôme, Christophe Vandier
Tight control of basal cytosolic Ca(2+) concentration is essential for cell survival and to fine-tune Ca(2+)-dependent cell functions. A way to control this basal cytosolic Ca(2+) concentration is to regulate membrane Ca(2+) channels including store-operated Ca(2+) channels and secondary messenger-operated channels linked to G-protein-coupled or tyrosine kinase receptor activation. Orai, with or without its reticular STIM partner and Transient Receptor Potential (TRP) proteins, were considered to be the main Ca(2+) channels involved...
May 17, 2017: European Biophysics Journal: EBJ
Luka Mesarec, Wojciech Góźdź, Samo Kralj, Miha Fošnarič, Samo Penič, Veronika Kralj-Iglič, Aleš Iglič
Biological membranes are composed of different components and there is no a priori reason to assume that all components are isotropic. It was previously shown that the anisotropic properties of membrane components may explain the stability of membrane tubular protrusions even without the application of external force. Our theoretical study focuses on the role of anisotropic membrane components in the stability of membrane tubular structures generated or stabilized by actin filaments. We show that the growth of the actin cytoskeleton inside the vesicle can induce the partial lateral segregation of different membrane components...
May 9, 2017: European Biophysics Journal: EBJ
Marc-Antoine Sani, Siobhan Carne, Sarah A Overall, Alexandre Poulhazan, Frances Separovic
Antimicrobial peptides (AMPs) may act by targeting the lipid membranes and disrupting the bilayer structure. In this study, three AMPs from the skin of Australian tree frogs, aurein 1.2, maculatin 1.1 and caerin 1.1, were investigated against Gram-negative Escherichia coli, Gram-positive Staphylococcus aureus, and vesicles that mimic their lipid compositions. Furthermore, equimolar mixtures of the peptides were tested to identify any synergistic interactions in antimicrobial activity. Minimum inhibition concentration and minimum bactericidal concentration assays showed significant activity against S...
May 6, 2017: European Biophysics Journal: EBJ
Eva Žerovnik
Cystatins and crystallins are both neuroprotective proteins. Except for their function as cysteine cathepsins inhibitors, cystatins are Aβ binding proteins and presumably protect neurons from intracellular Aβ and extracellular Aβ plaques. Pathological mutations of cystatin C cause amyloid angiopathy. Crystallins, known as small heat shock proteins, bind not only Aβ peptide but also other crystallins in the eye lens and prevent their aggregation. Mutations in crystallins cause cataracts and myopathies. Cross-interactions between amyloidogenic proteins, intrinsically disordered and folded proteins, can also occur...
May 6, 2017: European Biophysics Journal: EBJ
S S Voznesenskiy, A Yu Popik, E L Gamayunov, T Yu Orlova, V Zh Markina, I V Postnova, A Yu Shchipunov
The biocompatible silica precursor tetrakis(2-hydroxyethyl)orthosilicate with ethylene glycol residues was used instead of the common alcohol-containing tetraethoxysilane for the first time to prepare a biorecognition element by entrapping the marine microalga Porphyridium purpureum into a silica matrix by a one-stage sol-gel procedure at conditions (pH, ionic strength, and temperature) appropriate for living cells. We show that the microalga immobilized in this way fully maintains its viability and functionality...
May 5, 2017: European Biophysics Journal: EBJ
Anna B Druzhko, Tatyana V Dyukova, Sergey K Pirutin
This review presents the results of studies concerning some factors that affect the process of photoinduced hydroxylaminolysis (PHA) in bacteriorhodopsin (BR) and different BR-based media. We consider the peculiar properties of the PHA reaction in water suspensions of BR and BR-based media depending on variation in PHA ingredients, and in particular the use of O-substituted hydroxylamines instead of hydroxylamine hydrochloride. In addition, we discuss how such factors as preliminary ultra-sonication affect the reaction of PHA in the course of BR bleaching and following the reconstitution of bacterioopsin...
May 4, 2017: European Biophysics Journal: EBJ
Jiří Kozelka
Lone pair-π interactions are now recognized as a supramolecular bond whose existence in biological systems is documented by a growing number of examples. They are commonly attributed to electrostatic forces. This review attempts to highlight some recent discoveries evidencing the important role which lone pair-π interactions, and anion-π interactions in particular, play in stabilizing the structure and affecting the function of biomolecules. Special attention is paid to studies exploring the physical origin of these at first glance counterintuitive interactions between a lone pair of electrons of one residue and the π-cloud of another...
May 2, 2017: European Biophysics Journal: EBJ
Carla Pallavicini, Alejandro Monastra, Nicolás González Bardeci, Diana Wetzler, Valeria Levi, Luciana Bruno
Microtubules are filamentous biopolymers involved in essential biological processes. They form key structures in eukaryotic cells, and thus it is very important to determine the mechanisms involved in the formation and maintenance of the microtubule network. Microtubule bucklings are transient and localized events commonly observed in living cells and characterized by a fast bending and its posterior relaxation. Active forces provided by molecular motors have been indicated as responsible for most of these rapid deformations...
April 19, 2017: European Biophysics Journal: EBJ
G Kopylova, S Nabiev, D Shchepkin, S Bershitsky
Carbonylation induced by hyperthyroidism suppresses force generation of skeletal myosin and sliding velocity of actin filaments in an in vitro motility assay. However, its effects on cardiac myosin at the molecular level have not been studied. Hyperthyroidism induces a change in expression of myosin heavy chains in ventricles, which may mask the effect of oxidation. In contrast to ventricular myosin, expression of myosin heavy chains in the atrium does not change upon hyperthyroidism and enables investigation of the effect of oxidation on cardiac myosin...
April 13, 2017: European Biophysics Journal: EBJ
Martin B Ulmschneider, Jakob P Ulmschneider, J Alfredo Freites, Gunnar von Heijne, Douglas J Tobias, Stephen H White
Hydrophobic amino acids are abundant in transmembrane (TM) helices of membrane proteins. Charged residues are sparse, apparently due to the unfavorable energetic cost of partitioning charges into nonpolar phases. Nevertheless, conserved arginine residues within TM helices regulate vital functions, such as ion channel voltage gating and integrin receptor inactivation. The energetic cost of arginine in various positions along hydrophobic helices has been controversial. Potential of mean force (PMF) calculations from atomistic molecular dynamics simulations predict very large energetic penalties, while in vitro experiments with Sec61 translocons indicate much smaller penalties, even for arginine in the center of hydrophobic TM helices...
April 13, 2017: European Biophysics Journal: EBJ
Akira Sato, Chiemi Ueda, Ryu Kimura, Chisato Kobayashi, Yoji Yamazaki, Keiichi Ebina
Modifications of low-density lipoprotein (LDL), such as oxidation and aggregation, and angiotensin (Ang) peptides are involved in the pathogenesis of atherosclerosis. Here, we investigated the relationship between one of the Ang peptides, AngII, and two LDL modifications, oxidation and aggregation. Using polyacrylamide gel electrophoresis and aggregation assays, we noted that AngII markedly induced the aggregation of LDL and oxidized LDL (Ox-LDL), and bound to both the aggregated and non-aggregated forms. In contrast, a peptide (AngIII) formed by deletion of N-terminal Asp of AngII induced the aggregation of Ox-LDL but not LDL...
April 11, 2017: European Biophysics Journal: EBJ
Robert W Janes
Proteins tend to have defined conformations, a key factor in enabling their function. Atomic resolution structures of proteins are predominantly obtained by either solution nuclear magnetic resonance (NMR) or crystal structure methods. However, when considering a protein whose structure has been determined by both these approaches, on many occasions, the resultant conformations are subtly different, as illustrated by the examples in this study. The solution NMR approach invariably results in a cluster of structures whose conformations satisfy the distance boundaries imposed by the data collected; it might be argued that this is evidence of the dynamics of proteins when in solution...
April 3, 2017: European Biophysics Journal: EBJ
A Steuer, K Wende, P Babica, J F Kolb
Nanosecond pulsed electric fields (nsPEFs) applied to cells can induce different biological effects depending on pulse duration and field strength. One known process is the induction of apoptosis whereby nsPEFs are currently investigated as a novel cancer therapy. Another and probably related change is the breakdown of the cytoskeleton. We investigated the elasticity of rat liver epithelial cells WB-F344 in a monolayer using atomic force microscopy (AFM) with respect to the potential of cells to undergo malignant transformation or to develop a potential to metastasize...
April 1, 2017: European Biophysics Journal: EBJ
Maïwenn Beaugrand, Alexandre A Arnold, Steve Bourgault, Philip T F Williamson, Isabelle Marcotte
The hERG channel is a voltage-gated potassium channel found in cardiomyocytes that contributes to the repolarization of the cell membrane following the cardiac action potential, an important step in the regulation of the cardiac cycle. The lipids surrounding K(+) channels have been shown to play a key role in their regulation, with anionic lipids shown to alter gating properties. In this study, we investigate how anionic lipids interact with the pore helix of hERG and compare the results with those from Kv1...
March 17, 2017: European Biophysics Journal: EBJ
Patricia S Kumagai, Ricardo DeMarco, Jose L S Lopes
The unordered secondary structural content of an intrinsically disordered protein (IDP) is susceptible to conformational changes induced by many different external factors, such as the presence of organic solvents, removal of water, changes in temperature, binding to partner molecules, and interaction with lipids and/or other ligands. In order to characterize the high-flexibility nature of an IDP, circular dichroism (CD) spectroscopy is a particularly useful method due to its capability of monitoring both subtle and remarkable changes in different environments, relative ease in obtaining measurements, the small amount of sample required, and the capability for sample recovery (sample not damaged) and others...
March 3, 2017: European Biophysics Journal: EBJ
Ying Wang, Helene Schellenberg, Volker Walhorn, Katja Toensing, Dario Anselmetti
Fluorescent dyes are broadly used in many biotechnological applications to detect and visualize DNA molecules. However, their binding to DNA alters the structural and nanomechanical properties of DNA and, thus, interferes with associated biological processes. In this work we employed magnetic tweezers and fluorescence spectroscopy to investigate the binding of PicoGreen to DNA at room temperature in a concentration-dependent manner. PicoGreen is an ultrasensitive quinolinium nucleic acid stain exhibiting hardly any background signal from unbound dye molecules...
March 1, 2017: European Biophysics Journal: EBJ
Patrizia Iavicoli, François Rossi, Baptiste Lamarre, Angelo Bella, Maxim G Ryadnov, Luigi Calzolai
Peptide-lipid interactions support a variety of biological functions. Of particular interest are those that underpin fundamental mechanisms of innate immunity that are programmed in host defense or antimicrobial peptide sequences found virtually in all multicellular organisms. Here we synthetically modulate antimicrobial peptide-lipid interactions using an archetypal helical antimicrobial peptide and synthetic membranes mimicking bacterial and mammalian membranes in solution. We probe these interactions as a function of membrane-induced folding, membrane stability and peptide-lipid ratios using a correlative approach encompassing light scattering and spectroscopy measurements such as circular dichroism spectroscopy, fluorescence and nuclear magnetic resonance spectroscopy...
May 2017: European Biophysics Journal: EBJ
Anatoliy I Dragan, Christopher M Read, Colyn Crane-Robinson
Structural modifications to interacting systems frequently lead to changes in both the enthalpy (heat) and entropy of the process that compensate each other, so that the Gibbs free energy is little changed: a major barrier to the development of lead compounds in drug discovery. The conventional explanation for such enthalpy-entropy compensation (EEC) is that tighter contacts lead to a more negative enthalpy but increased molecular constraints, i.e., a compensating conformational entropy reduction. Changes in solvation can also contribute to EEC but this contribution is infrequently discussed...
May 2017: European Biophysics Journal: EBJ
Wallance Moreira Pazin, Danilo da Silva Olivier, Neus Vilanova, Ana Paula Ramos, Ilja Karina Voets, Ademilson Espencer Egea Soares, Amando Siuiti Ito
Green propolis, a mixture of beeswax and resinous compounds processed by Apis mellifera, displays several pharmacological properties. Artepillin C, the major compound in green propolis, consists of two prenylated groups bound to a phenyl group. Several studies have focused on the therapeutic effects of Artepillin C, but there is no evidence that it interacts with amphiphilic aggregates to mimic cell membranes. We have experimentally and computationally examined the interaction between Artepillin C and model membranes composed of dimyristoylphosphatidylcholine (DMPC) because phosphatidylcholine (PC) is one of the most abundant phospholipids in eukaryotic cell membranes...
May 2017: European Biophysics Journal: EBJ
Anna Mularski, Jonathan Wilksch, Eric Hanssen, Jian Li, Takehiro Tomita, Sacha James Pidot, Tim Stinear, Frances Separovic, Dick Strugnell
Atomic force microscopy measurements of capsule thickness revealed that that the wild-type Klebsiella pneumoniae AJ218 capsular polysaccharides were rearranged by exposure to colistin. The increase in capsule thickness measured near minimum inhibitory/bactericidal concentration (MIC/MBC) is consistent with the idea that colistin displaces the divalent cations that cross-bridge adjacent lipopolysaccharide (LPS) molecules through the capsule network. Cryo-electron microscopy demonstrated that the measured capsule thickness at near MIC/MBC of 1...
May 2017: European Biophysics Journal: EBJ
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