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Biophysical Journal

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https://www.readbyqxmd.com/read/28821322/saxs-versus-fret-a-matter-of-heterogeneity
#1
Kiersten M Ruff, Alex S Holehouse
No abstract text is available yet for this article.
August 15, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28803626/putting-the-piezolyte-hypothesis-under-pressure
#2
Christina M Papini, Pranav P Pandharipande, Catherine A Royer, George I Makhatadze
A group of small molecules that stabilize proteins against high hydrostatic pressure has been classified as piezolytes, a subset of stabilizing cosolutes. This distinction would imply that piezolytes counteract the effects of high hydrostatic pressure through effects on the volumetric properties of the protein. The purpose of this study was to determine if cosolutes proposed to be piezolytes have an effect on the volumetric properties of proteins through direct experimental measurements of volume changes upon unfolding of model proteins lysozyme and ribonuclease A, in solutions containing varying cosolute concentrations...
August 10, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28801104/n-alcohol-length-governs-shift-in-lo-ld-mixing-temperatures-in-synthetic-and-cell-derived-membranes
#3
Caitlin E Cornell, Nicola L C McCarthy, Kandice R Levental, Ilya Levental, Nicholas J Brooks, Sarah L Keller
A persistent challenge in membrane biophysics has been to quantitatively predict how membrane physical properties change upon addition of new amphiphiles (e.g., lipids, alcohols, peptides, or proteins) in order to assess whether the changes are large enough to plausibly result in biological ramifications. Because of their roles as general anesthetics, n-alcohols are perhaps the best-studied amphiphiles of this class. When n-alcohols are added to model and cell membranes, changes in membrane parameters tend to be modest...
August 9, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28797705/effects-of-hiv-1-gp41-derived-virucidal-peptides-on-virus-like-lipid-membranes
#4
Pablo Carravilla, Antonio Cruz, Itziar Martin-Ugarte, Itziar R Oar-Arteta, Johanna Torralba, Beatriz Apellaniz, Jesús Pérez-Gil, José Requejo-Isidro, Nerea Huarte, José L Nieva
Membrane fusion induced by the envelope glycoprotein enables the intracellular replication of HIV-1; hence, this process constitutes a major target for antiretroviral compounds. It has been proposed that peptides having propensity to interact with membrane interfaces might exert broad antiviral activity against enveloped viruses. To test this hypothesis, in this contribution we have analyzed the antiviral effects of peptides derived from the membrane-proximal external region and the transmembrane domain of the envelope glycoprotein subunit gp41, which display different degrees of interfacial hydrophobicity...
August 7, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28755756/brain-extracellular-space-the-final-frontier-of%C3%A2-neuroscience
#5
REVIEW
Charles Nicholson, Sabina Hrabětová
Brain extracellular space is the narrow microenvironment that surrounds every cell of the central nervous system. It contains a solution that closely resembles cerebrospinal fluid with the addition of extracellular matrix molecules. The space provides a reservoir for ions essential to the electrical activity of neurons and forms an intercellular chemical communication channel. Attempts to reveal the size and structure of the extracellular space using electron microscopy have had limited success; however, a biophysical approach based on diffusion of selected probe molecules has proved useful...
July 26, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28755755/tension-and-elasticity-contribute-to-fibroblast-cell-shape-in-three-dimensions
#6
Christoph A Brand, Marco Linke, Kai Weißenbruch, Benjamin Richter, Martin Bastmeyer, Ulrich S Schwarz
The shape of animal cells is an important regulator for many essential processes such as cell migration or division. It is strongly determined by the organization of the actin cytoskeleton, which is also the main regulator of cell forces. Quantitative analysis of cell shape helps to reveal the physical processes underlying cell shape and forces, but it is notoriously difficult to conduct it in three dimensions. Here we use direct laser writing to create 3D open scaffolds for adhesion of connective tissue cells through well-defined adhesion platforms...
July 26, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28750887/probing-the-interplay-between-dendritic-spine-morphology-and-membrane-bound-diffusion
#7
Max Adrian, Remy Kusters, Cornelis Storm, Casper C Hoogenraad, Lukas C Kapitein
Dendritic spines are protrusions along neuronal dendrites that harbor the majority of excitatory postsynapses. Their distinct morphology, often featuring a bulbous head and small neck that connects to the dendritic shaft, has been shown to facilitate compartmentalization of electrical and cytoplasmic signaling stimuli elicited at the synapse. The extent to which spine morphology also forms a barrier for membrane-bound diffusion has remained unclear. Recent simulations suggested that especially the diameter of the spine neck plays a limiting role in this process...
July 24, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28738989/membrane-curvature-and-lipid-composition-synergize-to-regulate-n-ras-anchor-recruitment
#8
Jannik B Larsen, Celeste Kennard, Søren L Pedersen, Knud J Jensen, Mark J Uline, Nikos S Hatzakis, Dimitrios Stamou
Proteins anchored to membranes through covalently linked fatty acids and/or isoprenoid groups play crucial roles in all forms of life. Sorting and trafficking of lipidated proteins has traditionally been discussed in the context of partitioning to membrane domains of different lipid composition. We recently showed that membrane shape/curvature can in itself mediate the recruitment of lipidated proteins. However, exactly how membrane curvature and composition synergize remains largely unexplored. Here we investigated how three critical structural parameters of lipids, namely acyl chain saturation, headgroup size, and acyl chain length, modulate the capacity of membrane curvature to recruit lipidated proteins...
July 21, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28734478/ph-dependent-membrane-interactions-of-the-histidine-rich-cell-penetrating-peptide-lah4-l1
#9
Justine Wolf, Christopher Aisenbrey, Nicole Harmouche, Jesus Raya, Philippe Bertani, Natalia Voievoda, Regine Süss, Burkhard Bechinger
The histidine-rich designer peptide LAH4-L1 exhibits antimicrobial and potent cell-penetrating activities for a wide variety of cargo including nucleic acids, polypeptides, adeno-associated viruses, and nanodots. The non-covalent complexes formed between the peptide and cargo enter the cell via an endosomal pathway where the pH changes from neutral to acidic. Here, we investigated the membrane interactions of the peptide with phospholipid bilayers and its membrane topology using static solid-state NMR spectroscopy...
July 19, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28734477/polarity-sensitive-probes-for-superresolution-stimulated-emission-depletion-microscopy
#10
Erdinc Sezgin, Falk Schneider, Victoria Zilles, Iztok Urbančič, Esther Garcia, Dominic Waithe, Andrey S Klymchenko, Christian Eggeling
The lateral organization of molecules in the cellular plasma membrane plays an important role in cellular signaling. A critical parameter for membrane molecular organization is how the membrane lipids are packed. Polarity-sensitive dyes are powerful tools to characterize such lipid membrane order, employing, for example, confocal and two-photon microscopy. The investigation of potential nanodomains, however, requires the use of superresolution microscopy. Here, we test the performance of the polarity-sensitive membrane dyes Di-4-ANEPPDHQ, Di-4-AN(F)EPPTEA, and NR12S in superresolution stimulated emission depletion microscopy...
July 19, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28734476/quantifying-the-interaction-between-egfr-dimers-and-grb2-in-live-cells
#11
Nuala Del Piccolo, Kalina Hristova
Adaptor proteins are a class of cytoplasmic proteins that bind to phosphorylated residues in receptor tyrosine kinases and trigger signaling cascades that control critically important cellular processes, such as cell survival, growth, differentiation, and motility. Here, we seek to characterize the interaction between epidermal growth factor receptor (EGFR) and the cytoplasmic adaptor protein growth factor receptor-bound protein 2 (Grb2) in a cellular context. To do so, we explore the utility of a highly biologically relevant model system, mammalian cells under reversible osmotic stress, and a recently introduced Förster resonance energy transfer microscopy method, fully quantified spectral imaging...
July 19, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28732557/a-negative-slope-conductance-of-the-persistent-sodium-current-prolongs-subthreshold-depolarizations
#12
Cesar C Ceballos, Antonio C Roque, Ricardo M Leão
Neuronal subthreshold voltage-dependent currents determine membrane properties such as the input resistance (Rin) and the membrane time constant (τm) in the subthreshold range. In contrast with classical cable theory predictions, the persistent sodium current (INaP), a non-inactivating mode of the voltage-dependent sodium current, paradoxically increases Rin and τm when activated. Furthermore, this current amplifies and prolongs synaptic currents in the subthreshold range. Here, using a computational neuronal model, we showed that the creation of a region of negative slope conductance by INaP activation is responsible for these effects and the ability of the negative slope conductance to amplify and prolong Rin and τm relies on the fast activation of INaP...
July 18, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28712640/resident-calmodulin-primes-nmda-receptors-for-ca-2-dependent-inactivation
#13
Gary J Iacobucci, Gabriela K Popescu
N-methyl-d-aspartate (NMDA) receptors are glutamate- and glycine-gated channels that flux Na(+) and Ca(2+) into postsynaptic neurons during synaptic transmission. The resulting intracellular Ca(2+) transient is essential to physiological and pathological processes related to synaptic development, plasticity, and apoptosis. It also engages calmodulin (CaM) to reduce subsequent NMDA receptor activity in a process known as Ca(2+)-dependent inactivation (CDI). Here, we used whole-cell electrophysiology to measure CDI and computational modeling to dissect the sequence of events that underlies it...
July 14, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28697898/fusion-domains-guide-the-oriented-insertion-of-light-driven-proton-pumps-into-liposomes
#14
Noah Ritzmann, Johannes Thoma, Stephan Hirschi, David Kalbermatter, Dimitrios Fotiadis, Daniel J Müller
One major objective of synthetic biology is the bottom-up assembly of minimalistic nanocells consisting of lipid or polymer vesicles as architectural scaffolds and of membrane and soluble proteins as functional elements. However, there is no reliable method to orient membrane proteins reconstituted into vesicles. Here, we introduce a simple approach to orient the insertion of the light-driven proton pump proteorhodopsin (PR) into liposomes. To this end, we engineered red or green fluorescent proteins to the N- or C-terminus of PR, respectively...
July 8, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28697897/measuring-protein-binding-to-lipid-vesicles-by-fluorescence-cross-correlation-spectroscopy
#15
Daniela Krüger, Jan Ebenhan, Stefan Werner, Kirsten Bacia
Fluorescence correlation spectroscopy has been previously used to investigate peptide and protein binding to lipid membranes, as it allows for very low amounts of sample, short measurement times and equilibrium binding conditions. Labeling only one of the binding partners, however, comes with certain drawbacks, as it relies on identifying binding events by a change in diffusion coefficient. Since peptide and protein aggregation can obscure specific binding, and since non-stoichiometric binding necessitates the explicit choice of a statistical distribution for the number of bound ligands, we additionally label the liposomes and perform dual-color fluorescence cross-correlation spectroscopy (dcFCCS)...
July 8, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28697896/binding-kinetics-and-lateral-mobility-of-hsv-1-on-end-grafted-sulfated-glycosaminoglycans
#16
Nadia Peerboom, Stephan Block, Noomi Altgärde, Olov Wahlsten, Stephanie Möller, Matthias Schnabelrauch, Edward Trybala, Tomas Bergström, Marta Bally
Many viruses, including herpes simplex (HSV), are recruited to their host cells via interaction between their envelope glycoproteins and cell-surface glycosaminoglycans (GAGs). This initial attachment is of a multivalent nature, i.e., it requires the establishment of multiple bonds between amino acids of viral glycoproteins and sulfated saccharides on the GAG chain. To gain understanding of how this binding process is modulated, we performed binding kinetics and mobility studies using end-grafted GAG chains that mimic the end attachment of these chains to proteoglycans...
July 8, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28647061/vesicle-fusion-mediated-by-solanesol-anchored-dna
#17
Kristina M Flavier, Steven G Boxer
Fusion between two lipid bilayers is one of the central processes in cell biology, playing a key role in endocytosis, exocytosis, and vesicle transport. We have previously developed a model system that uses the hybridization of complementary DNA strands to model the formation of the SNARE four-helix bundle that mediates synaptic vesicle fusion and used it to study vesicle fusion to a tethered lipid bilayer. Using single vesicle assays, 70% of observed fusion events in the DNA-lipid system are arrested at the hemifusion stage, whereas only 5% eventually go to full fusion...
June 21, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28629620/effects-of-inhibiting-vps4-support-a-general-role-for-escrts-in-extracellular-vesicle-biogenesis
#18
Charles E Jackson, Benjamin S Scruggs, Jean E Schaffer, Phyllis I Hanson
Extracellular vesicles (EVs) are proposed to play important roles in intercellular communication. Two classes of EVs can be distinguished based on their intracellular origin. Exosomes are generated within endosomes and released when these fuse with the plasma membrane, whereas ectosomes bud directly from the plasma membrane. Studies of EV function have been hindered by limited understanding of their biogenesis. Components of the endosomal sorting complex required for transport (ESCRT) machinery play essential roles in topologically equivalent processes at both the endosome and the plasma membrane and are consistently recovered in EVs, but whether they are generally required to produce EVs is still debated...
June 16, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28629619/slow-interconversion-in-a-heterogeneous-unfolded-state-ensemble-of-outer-membrane-phospholipase-a
#19
Georg Krainer, Pablo Gracia, Erik Frotscher, Andreas Hartmann, Philip Gröger, Sandro Keller, Michael Schlierf
Structural and dynamic investigations of unfolded proteins are important for understanding protein-folding mechanisms as well as the interactions of unfolded polypeptide chains with other cell components. In the case of outer-membrane proteins (OMPs), unfolded-state properties are of particular physiological relevance, because these proteins remain unfolded for extended periods of time during their biogenesis and rely on interactions with binding partners to support proper folding. Using a combination of ensemble and single-molecule spectroscopy, we have scrutinized the unfolded state of outer-membrane phospholipase A (OmpLA) to provide a detailed view of its structural dynamics on timescales from nanoseconds to milliseconds...
June 16, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28793229/response-to-comment-to-the-editor
#20
EDITORIAL
Theodore W Randolph
No abstract text is available yet for this article.
August 8, 2017: Biophysical Journal
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