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Membrane curvature

Kenneth Lindegaard Madsen, Rasmus Herlo
The shape and composition of a membrane directly regulate the localization, activity, and signaling properties of membrane associated proteins. Proteins that both sense and generate membrane curvature, e.g., through amphiphilic insertion motifs, potentially engage in recursive binding dynamics, where the recruitment of the protein itself changes the properties of the membrane substrate. Simple geometric models of membrane curvature interactions already provide prediction tools for experimental observations, however these models are treating curvature sensing and generation as separated phenomena...
February 8, 2017: Membranes
Abdallah Daddi-Moussa-Ider, Stephan Gekle
We use the image solution technique to compute the leading order frequency-dependent self-mobility function of a small solid particle moving perpendicular to the surface of a spherical capsule whose membrane possesses shearing and bending rigidities. Comparing our results with those obtained earlier for an infinitely extended planar elastic membrane, we find that membrane curvature leads to the appearance of a prominent additional peak in the mobility. This peak is attributed to the fact that the shear resistance of the curved membrane involves a contribution from surface-normal displacements, which is not the case for planar membranes...
January 2017: Physical Review. E
Yanjie Xu, Jixiang Xia, Suxuan Liu, Sam Stein, Cueto Ramon, Hang Xi, Luqiao Wang, Xinyu Xiong, Lixiao Zhang, Dingwen He, William Yang, Xianxian Zhao, Xiaoshu Cheng, Xiaofeng Yang, Hong Wang
Endocytosis is a cellular process mostly responsible for membrane receptor internalization. Cell membrane receptors bind to their ligands and form a complex which can be internalized. We previously proposed that F-BAR protein initiates membrane curvature and mediates endocytosis via its binding partners. However, F-BAR protein partners involved in membrane receptor endocytosis and the regulatory mechanism remain unknown. In this study, we established database mining strategies to explore mechanisms underlying receptor-related endocytosis...
March 1, 2017: Frontiers in Bioscience (Landmark Edition)
Shifra Rokach, Maria Francesca Ottaviani, Alexander I Shames, Abraham Aserin, Nissim Garti
Dendrimer nanostructures are of eminent interest in biomedical applications because of their uniform and well-defined molecular size and shape, and their ability to cross cell membranes and reduce the risk of premature clearance from the human body. Dendrimers perform as gene and drug carriers and have also shown significant therapeutic properties for treating cancer and neurodegenerative diseases. A complex drug delivery system, based on a dendrimer solubilized in the aqueous core of a water-in-oil (W/O) microemulsion (ME) along with the drug may combine the advantages of both dendrimers and MEs to provide better control of drug release...
February 14, 2017: Journal of Physical Chemistry. B
J-D Debus, M Mendoza, S Succi, H J Herrmann
Fluid dynamics in intrinsically curved geometries is encountered in many physical systems in nature, ranging from microscopic bio-membranes all the way up to general relativity at cosmological scales. Despite the diversity of applications, all of these systems share a common feature: the free motion of particles is affected by inertial forces originating from the curvature of the embedding space. Here we reveal a fundamental process underlying fluid dynamics in curved spaces: the free motion of fluids, in the complete absence of solid walls or obstacles, exhibits loss of energy due exclusively to the intrinsic curvature of space...
February 14, 2017: Scientific Reports
Jiali Zhai, Nhiem Tran, Sampa Sarkar, Celesta Fong, Xavier Mulet, Calum J Drummond
We report here the lyotropic liquid crystalline phase behaviour of two lipid nanoparticulate systems containing mixtures of monoolein, capric acid and saturated diacyl phosphatidylcholines dispersed by the Pluronic F127 block copolymer. Synchrotron small angle X-ray scattering (SAXS) was used to screen the phase behaviour of a library of lipid nanoparticles in a high-throughput manner. It was found that adding capric acid and phosphatidylcholines had opposing effects on the spontaneous membrane curvature of the monoolein lipid layer and hence the internal mesophase of the final nanoparticles...
February 13, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Mouhedine Cheniour, Jonathan Brewer, Luis Bagatolli, Olivier Marcillat, Thierry Granjon
BACKGROUND: Mitochondrial Creatine kinase (mtCK) is highly abundant in mitochondria; its quantity is equimolecular to the Adenylic Nucleotide Translocator and represents 1% of the mitochondrial proteins. It is a multitask protein localized in the mitochondria intermembrane space where it binds to the specific cardiolipin (CL) phospholipid. If mtCK was initially thought to be exclusively implicated in energy transfer between mitochondria and cytosol through a mechanism referred to as the phosphocreatine shuttle, several recent studies suggested an additional role in maintaining mitochondria membrane structure...
February 6, 2017: Biochimica et Biophysica Acta
Sebastian Kruss, Daniel P Salem, Lela Vuković, Barbara Lima, Emma Vander Ende, Edward S Boyden, Michael S Strano
Intercellular communication via chemical signaling proceeds with both spatial and temporal components, but analytical tools, such as microfabricated electrodes, have been limited to just a few probes per cell. In this work, we use a nonphotobleaching fluorescent nanosensor array based on single-walled carbon nanotubes (SWCNTs) rendered selective to dopamine to study its release from PC12 neuroprogenitor cells at a resolution exceeding 20,000 sensors per cell. This allows the spatial and temporal dynamics of dopamine release, following K(+) stimulation, to be measured at exceedingly high resolution...
February 8, 2017: Proceedings of the National Academy of Sciences of the United States of America
J M H Kroes, A Fasolino, M I Katsnelson
Using density functional theory, we study proton permeation through graphene and hexagonal boron nitride. We consider several factors influencing the barriers for permeation, including structural optimization, the role of the solvent, surface curvature and proton transport through hydrogenated samples. Furthermore, we discuss the ground state charge transfer from the membrane to the proton and the strong tendency for bond formation. If the process is assumed to be slow we find that none of these effects lead to a satisfactory answer to the observed discrepancies between theory and experiment...
February 8, 2017: Physical Chemistry Chemical Physics: PCCP
Zhiwei Wang, Zengming Zhang, Wei Liu, Zhong Lin Wang
We report an approach developed for deriving 3D structural information of 2D membrane folds based on the recently-established quantitative transmission electron microscopy (TEM) in combination with density functional theory (DFT) calculations. Systematic multislice simulations reveal that the membrane folding leads to sufficiently strong electron scattering which enables a precise determination of bending radius. The image contrast depends also on the folding angles of 2D materials due to the variation of projection potentials, which however exerts much smaller effect compared with the bending radii...
January 12, 2017: Micron: the International Research and Review Journal for Microscopy
Deepti Dabral, Jens R Coorssen
Membrane fusion is a fundamental molecular mechanism by which two apposed membrane bilayers coalesce in rapid, transient steps that enable the successive merging of the outer and inner leaflets allowing lipid intermixing and subsequent mixing of the two previously separate compartments. The actual membrane merger mechanism - fusion, by definition - is conceptualized to be protein- or lipid-centric. According to the widely vetted stalk-pore hypothesis, membrane fusion proceeds via high curvature lipid intermediates...
January 25, 2017: International Journal of Biochemistry & Cell Biology
Barry W Ninham, Kåre Larsson, Pierandrea Lo Nostro
Hofmeister, specific ion effects, hydration and van der Waals forces at and between interfaces are factors that determine curvature and microstructure in self assembled aggregates of surfactants and lipids; and in microemulsions. Lipid and surfactant head group interactions and between aggregates vary enormously and are highly specific. They act on the hydrophilic side of a bilayer, micelle or other self assembled aggregate. It is only over the last three decades that the origin of Hofmeister effects has become generally understood...
January 15, 2017: Colloids and Surfaces. B, Biointerfaces
Remo Friedrich, Stephan Block, Mohammadreza Alizadehheidari, Susanne Heider, Joachim Fritzsche, Elin K Esbjörner, Fredrik Westerlund, Marta Bally
We present a nanofluidic device for fluorescence-based detection and characterization of small lipid vesicles on a single particle basis. The device works like a nano flow cytometer where individual vesicles are visualized by fluorescence microscopy while passing through parallel nanochannels in a pressure-driven flow. An experiment requires less than 20 μl sample volume to quantify both the vesicle content and the fluorescence signals emitted by individual vesicles. We show that the device can be used to accurately count the number of fluorescent synthetic lipid vesicles down to a vesicle concentration of 170 fM...
January 27, 2017: Lab on a Chip
Julian E Hassinger, George Oster, David G Drubin, Padmini Rangamani
A critical step in cellular-trafficking pathways is the budding of membranes by protein coats, which recent experiments have demonstrated can be inhibited by elevated membrane tension. The robustness of processes like clathrin-mediated endocytosis (CME) across a diverse range of organisms and mechanical environments suggests that the protein machinery in this process has evolved to take advantage of some set of physical design principles to ensure robust vesiculation against opposing forces like membrane tension...
January 26, 2017: Proceedings of the National Academy of Sciences of the United States of America
Srishti Dar, Sukrut C Kamerkar, Thomas J Pucadyil
The process of membrane fission is fundamental to diverse cellular processes such as nutrient uptake, synaptic transmission and organelle biogenesis, and it involves the localized application of curvature stress to a tubular membrane intermediate, forcing it to undergo scission. Alternative techniques for creating such substrates necessitate the use of micromanipulators or sophisticated optical traps and require a high level of technical expertise. We present a facile method to generate an array of membrane tubes supported on a passivated glass coverslip, which we refer to as supported membrane tubes (SMrTs)...
February 2017: Nature Protocols
Timur R Galimzyanov, Peter I Kuzmin, Peter Pohl, Sergey A Akimov
Phase separation in biological membranes plays an important role in protein targeting and transmembrane signaling. Its occurrence in both membrane leaflets commonly gives rise to matching liquid or liquid-ordered domains in the opposing monolayers. The underlying mechanism of such co-localization is not fully understood. The decrease of the line tension around the thicker ordered domain constitutes an important driving force. Yet, robust domain coupling requires an additional energy source, which we have now identified as thermal undulations...
January 24, 2017: Biophysical Journal
Karl Lohner
The increase of pathogens being resistant to antibiotics represents a global health problem and therefore it is a pressing need to develop antibiotics with novel mechanisms of action. Host defense peptides, which have direct antimicrobial activity (also termed antimicrobial peptides) or immune modulating activity, are valuable template structures for the development of such compounds. Antimicrobial peptides exhibit remarkably different structures as well as biological activity profiles with multiple targets...
2017: Current Topics in Medicinal Chemistry
Taylor B Updegrove, Kumaran S Ramamurthi
Bacterial cells are highly organized at a molecular level. Understanding how specific proteins localize to their proper subcellular address has been a major challenge in bacterial cell biology. One mechanism, which appears to be increasingly more common, is the use of 'geometric cues' for protein localization. In this model, certain shape-sensing proteins recognize, and preferentially embed into, either negatively or positively curved (concave or convex, respectively) membranes. Here, we review examples of bacterial proteins that reportedly localize by sensing geometric cues and highlight emerging mechanistic understandings of how proteins may recognize subtle differences in membrane curvature...
January 19, 2017: Current Opinion in Microbiology
Thomas G Meikle, Alexandru Zabara, Lynne J Waddington, Frances Separovic, Calum J Drummond, Charlotte E Conn
The inverse bicontinuous lipidic cubic phase offers a simple and robust membrane mimetic with the ability to encapsulate peptides, potentially increasing bioavailability, while also offering a platform from which functionalized, targeted nanoparticles can be developed. Herein we have investigated the use of a number of cubic phase nanoparticle systems with encapsulated antimicrobial peptides gramicidin A', melittin, and alamethicin. The optimal peptide loading ranges, over which cubic symmetry was retained, were determined using small angle X-ray scattering...
January 8, 2017: Colloids and Surfaces. B, Biointerfaces
William T Heller, Durgesh K Rai
HIV-1, like other enveloped viruses, undergoes fusion with the cell membrane to infect it. Viral coat proteins are thought to bind the virus to the membrane and actively fuse the viral and cellular membranes together. The actual molecular mechanism of fusion is challenging to visualize, resulting in the use of model systems. Here, the bilayer curvature modifying properties of a synthetic variant of the HIV-1 gp41 fusion peptide with lipid bilayer vesicles composed of a mixture of dimyristoyl phosphatidylcholine (DMPC) and dimyristoyl phosphatidylserine (DMPS) were studied...
January 16, 2017: Chemistry and Physics of Lipids
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