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Membrane curvature

Jeevan B Gc, Bernard S Gerstman, Robert V Stahelin, Prem P Chapagain
The Ebola virus is a lipid-enveloped virus that obtains its lipid coat from the plasma membrane of the host cell it infects during the budding process. The Ebola virus protein VP40 localizes to the inner leaflet of the plasma membrane and forms the viral matrix, which provides the major structure for the Ebola virus particles. VP40 is initially a dimer that rearranges to a hexameric structure that mediates budding. VP40 hexamers and larger filaments have been shown to be stabilized by PI(4,5)P2 in the plasma membrane inner leaflet...
October 19, 2016: Physical Chemistry Chemical Physics: PCCP
Joseph D Unsay, Katia Cosentino, Katharina Sporbeck, Ana J García-Sáez
Bcl-2 proteins are key regulators of the mitochondrial outer membrane (MOM) permeabilization that mediates apoptosis. During apoptosis, Bid is cleaved (cBid) and translocates to the MOM, where it activates Bax. Bax then oligomerizes and induces MOM permeabilization. However, little is known about how these proteins affect membrane organization aside from pore formation. In previous studies, we have shown that both cBid and Bax are able to remodel membranes and stabilize curvature. Here, we dissected the independent effects of Bax and cBid on supported lipid structures mimicking the mitochondrial composition by means of atomic force spectroscopy...
October 15, 2016: Biochimica et Biophysica Acta
Zhiming Chen, Chen Zhu, Curtis J Kuo, Jaclyn Robustelli, Tobias Baumgart
N-BAR proteins such as endophilin are thought to bend lipid membranes via scaffolding (the molding of membranes through the crescent protein shape) and membrane insertion (also called wedging) of amphipathic helices. However, the contributions from these distinct mechanisms to membrane curvature generation and sensing have remained controversial. Here we quantitatively demonstrate that the amphipathic N-terminal H0 helix of endophilin is important for recruiting this protein to the membrane, but does not contribute significantly to its intrinsic membrane curvature generation capacity...
October 18, 2016: Journal of the American Chemical Society
Juul Verberne, Frank Risis, Luke Campbell, Scott Chambers, Stephen O'Leary
HYPOTHESIS: Scala tympani morphology influences the insertion dynamics and intra-scalar position of straight electrode arrays. BACKGROUND: Hearing preservation is the goal of cochlear implantation with current thin straight electrode arrays. These hug the lateral wall, facilitating full, atraumatic insertions. However, most studies still report some postoperative hearing loss. This study explores the influence of scala tympani morphology on array position relative to the basilar membrane and its possible contribution to postoperative hearing loss...
October 12, 2016: Otology & Neurotology
Xuejuan Liu, Falin Tian, Tongtao Yue, Xianren Zhang, Chongli Zhong
The shape deformation of membrane nanotubes is studied by a combination of theoretical analysis and molecular simulation. First we perform free energy analysis to demonstrate the effects of various factors on two ideal states for the pearling transition, and then we carry out dissipative particle dynamics simulations, through which various types of membrane tube deformation are found, including membrane pearling, buckling, and bulging. Different models for inducing tube deformation, including the osmotic pressure, area difference and spontaneous curvature models, are considered to investigate tubular instabilities...
October 17, 2016: Soft Matter
Adam Kawałek, Chandhuru Jagadeesan, Ida J van der Klei
The non-bilayer forming lipids cardiolipin (CL) and phosphatidylethanolamine (PE) modulate membrane curvature, facilitate membrane fusion and affect the stability and function of membrane proteins. Yeast peroxisomal membranes contain significant amounts of CL and PE. We analysed the effect of CL deficiency and PE depletion on peroxisome biogenesis and proliferation in Saccharomyces cerevisiae. Our data indicate that deletion of CRD1, which encodes cardiolipin synthase, does not affect peroxisome biogenesis or abundance, both at peroxisome repressing (glucose) or inducing (oleate) growth conditions...
October 13, 2016: Biochemical and Biophysical Research Communications
Jean Wolff, Shigeyuki Komura, David Andelman
We propose a model that accounts for the budding transition of asymmetric two-component lipid domains, where the two monolayers (leaflets) have different average compositions controlled by independent chemical potentials. Assuming a coupling between the local curvature and local lipid composition in each of the leaflets, we discuss the morphology and thermodynamic behavior of asymmetric lipid domains. The membrane free-energy contains three contributions: the bending energy, the line tension, and a Landau free-energy for a lateral phase separation...
September 2016: Physical Review. E
F G Dupuy, S P Fernández Bordín, B Maggio, R G Oliveira
Ceramides constitute a group of lipids with usually high melting temperature that also favor negative curvature in membranes when mixed with other lipids. The short chain C10:0 ceramide is an asymmetric lipid which consists of an 18 carbon sphingosine base N-acylated with decanoic acid. According to high sensitivity differential scanning calorimetry, it shows a minor exothermic peak at 61°C and a main endothermic transition at 75°C. By small angle X-ray scattering and polarized light microscopy we found that, at temperatures below the main transition, the fully hydrated lipid dispersions are arranged in a tridimensional structure corresponding to an inverted hexagonal phase...
October 5, 2016: Colloids and Surfaces. B, Biointerfaces
Colin James Stockdale Klaus, Krishnan Raghunathan, Emmanuele DiBenedetto, Anne K Kenworthy
Diffusion of particles in curved surfaces is inherently complex compared with diffusion in a flat membrane owing to the non-planarity of the surface. The consequence of such non-planar geometry on diffusion is poorly understood but is highly relevant in the case of cell membranes, which often adopt complex geometries. To address this question, we developed a new finite element approach to model diffusion on curved membrane surfaces based on solutions to Fick's law of diffusion and used this to study the effects of geometry on the entry of surface-bound particles into tubules by diffusion...
October 12, 2016: Molecular Biology of the Cell
Himani Agrawal, Liping Liu, Pradeep Sharma
Proteins embedded in soft biological membranes experience a long-range force mediated by elastic curvature deformations. The classical linearized Helfrich-Canham Hamiltonian based derivations reveal the nature of the force between a pair of proteins to be repulsive in the zero-temperature limit and the interaction potential is inversely proportional to the fourth power of the distance separating the inclusions. Such a result is the starting point to understand many-body interactions between proteins in biological membranes and the study of their clustering or, more broadly, self-organization...
October 11, 2016: Soft Matter
G C A da Hora, N L Archilha, J L S Lopes, D M Müller, K Coutinho, R Itri, T A Soares
Antimicrobial peptides (AMPs) are cationic peptides that kill bacteria with a broad spectrum of action, low toxicity to mammalian cells and exceptionally low rates of bacterial resistance. These features have led to considerable efforts in developing AMPs as an alternative antibacterial therapy. In vitro studies have shown that AMPs interfere with membrane bilayer integrity via several possible mechanisms, which are not entirely understood. We have performed the synthesis, membrane lysis measurements, and biophysical characterization of a novel hybrid peptide...
September 26, 2016: Soft Matter
Philip W Fowler, Jean Hélie, Anna Duncan, Matthieu Chavent, Heidi Koldsø, Mark S P Sansom
The ease with which a cell membrane can bend and deform is important for a wide range of biological functions. Peripheral proteins that induce curvature in membranes (e.g. BAR domains) have been studied for a number of years. Little is known, however, about the effect of integral membrane proteins on the stiffness of a membrane (characterised by the bending rigidity, Kc). We demonstrate by computer simulation that adding integral membrane proteins at physiological densities alters the stiffness of the membrane...
September 20, 2016: Soft Matter
A J Sodt, R M Venable, E Lyman, R W Pastor
The unique properties of the individual lipids that compose biological membranes together determine the energetics of the surface. The energetics of the surface, in turn, govern the formation of membrane structures and membrane reshaping processes, and thus they will underlie cellular-scale models of viral fusion, vesicle-dependent transport, and lateral organization relevant to signaling. The spontaneous curvature, to the best of our knowledge, is always assumed to be additive. We describe observations from simulations of unexpected nonadditive compositional curvature energetics of two lipids essential to the plasma membrane: sphingomyelin and cholesterol...
September 23, 2016: Physical Review Letters
Afshin Vahid, Timon Idema
Membrane tubes and tubular networks are ubiquitous in living cells. Inclusions like proteins are vital for both the stability and the dynamics of such networks. These inclusions interact via the curvature deformations they impose on the membrane. We analytically study the resulting membrane mediated interactions in strongly curved tubular membranes. We model inclusions as constraints coupled to the curvature tensor of the membrane tube. First, as special test cases, we analyze the interaction between ring- and rod-shaped inclusions...
September 23, 2016: Physical Review Letters
David J Lea-Smith, Maite L Ortiz-Suarez, Tchern Lenn, Dennis J Nurnberg, Laura L Baers, Matthew P Davey, Lucia Parolini, Roland G Huber, Charles A R Cotton, Giulia Mastroianni, Paolo Bombelli, Petra Ungerer, Tim J Stevens, Alison G Smith, Peter J Bond, Conrad W Mullineaux, Christopher J Howe
Cyanobacteria are intricately organized, incorporating an array of internal thylakoid membranes, the site of photosynthesis, into cells no larger than other bacteria. They also synthesize C15-C19 alkanes and alkenes, which results in substantial production of hydrocarbons in the environment. All sequenced cyanobacteria encode hydrocarbon biosynthesis pathways, suggesting an important, undefined physiological role for these compounds. Here we demonstrate that hydrocarbon deficient mutants of Synechococcus sp...
October 5, 2016: Plant Physiology
Jordi Gómez-Llobregat, Federico Elías-Wolff, Martin Lindén
No abstract text is available yet for this article.
October 4, 2016: Biophysical Journal
David A Quint, Ajay Gopinathan, Gregory M Grason
Motivated to understand the behavior of biological filaments interacting with membranes of various types, we employ a theoretical model for the shape and thermodynamics of intrinsically helical filaments bound to curved membranes. We show that filament-surface interactions lead to a host of nonuniform shape equilibria, in which filaments progressively unwind from their native twist with increasing surface interaction and surface curvature, ultimately adopting uniform-contact curved shapes. The latter effect is due to nonlinear coupling between elastic twist and bending of filaments on anisotropically curved surfaces such as the cylindrical surfaces considered here...
October 4, 2016: Biophysical Journal
Jan Steinkühler, Jaime Agudo-Canalejo, Reinhard Lipowsky, Rumiana Dimova
We introduce an experimental setup for modulating adhesion of giant unilamellar vesicles to a planar substrate. Adhesion is induced by the application of an external potential to a transparent indium tin oxide-coated electrode (the substrate), which enables single-vesicle studies. We demonstrate tunable and reversible adhesion of negatively charged vesicles. The adhesion energy at different potentials is calculated from the vesicle shape assessed with confocal microscopy. Two approaches for these estimates are employed: one based on the whole contour of the vesicle and a second based on the contact curvature of the membrane in the vicinity of the substrate...
October 4, 2016: Biophysical Journal
Françoise Hullin-Matsuda, Asami Makino, Motohide Murate, Toshihide Kobayashi
In this mini-review, we summarize current knowledge about the lipid-binding characteristics of two types of toxins used to visualize the membrane distribution of phosphoethanolamine-containing lipid species: the glycerophospholipid, phosphatidylethanolamine (PE) and the sphingolipid, ceramide phosphoethanolamine (CPE). The lantibiotic cinnamycin and the structurally-related peptide duramycin produced by some Gram-positive bacteria were among the first toxins characterized by their specificity for PE which is widely present in animal kingdoms from bacteria to mammals...
September 28, 2016: Biochimie
Jesse G McDaniel, Sriteja Mantha, Arun Yethiraj
The dynamics of water confined to nanometer-sized domains is important in a variety of applications ranging from proton exchange membranes to crowding effects in biophysics. In this work, we study the dynamics of water in gemini surfactant-based lyotropic liquid crystals (LLCs) using molecular dynamics simulations. These systems have well characterized morphologies, for example, hexagonal, gyroid, and lamellar, and the surfaces of the confining regions can be controlled by modifying the headgroup of the surfactants...
October 11, 2016: Journal of Physical Chemistry. B
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