Academic literature on the topic 'Biological membranes; Membrane proteins'

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Journal articles on the topic "Biological membranes; Membrane proteins"

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Ma, Yuanqing, Elizabeth Hinde, and Katharina Gaus. "Nanodomains in biological membranes." Essays in Biochemistry 57 (February 6, 2015): 93–107. http://dx.doi.org/10.1042/bse0570093.

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Lipid rafts are defined as cholesterol- and sphingomyelin-enriched membrane domains in the plasma membrane of cells that are highly dynamic and cannot be resolved with conventional light microscopy. Membrane proteins that are embedded in the phospholipid matrix can be grouped into raft and non-raft proteins based on their association with detergent-resistant membranes in biochemical assays. Selective lipid–protein interactions not only produce heterogeneity in the membrane, but also cause the spatial compartmentalization of membrane reactions. It has been proposed that lipid rafts function as platforms during cell signalling transduction processes such as T-cell activation (see Chapter 13 (pages 165–175)). It has been proposed that raft association co-localizes specific signalling proteins that may yield the formation of the observed signalling microclusters at the immunological synapses. However, because of the nanometre size and high dynamics of lipid rafts, direct observations have been technically challenging, leading to an ongoing discussion of the lipid raft model and its alternatives. Recent developments in fluorescence imaging techniques have provided new opportunities to investigate the organization of cell membranes with unprecedented spatial resolution. In this chapter, we describe the concept of the lipid raft and alternative models and how new imaging technologies have advanced these concepts.
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Whited, A. M., and A. Johs. "The interactions of peripheral membrane proteins with biological membranes." Chemistry and Physics of Lipids 192 (November 2015): 51–59. http://dx.doi.org/10.1016/j.chemphyslip.2015.07.015.

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Branton, Daniel. "Fracture faces of frozen membranes: 50th anniversary." Molecular Biology of the Cell 27, no. 3 (February 2016): 421–23. http://dx.doi.org/10.1091/mbc.e15-05-0287.

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In 1961, the development of an improved freeze-etching (FE) procedure to prepare rapidly frozen biological cells or tissues for electron microscopy raised two important questions. How does a frozen cell membrane fracture? What do the extensive face views of the cell’s membranes exposed by the fracture process of FE tell us about the overall structure of biological membranes? I discovered that all frozen membranes tend to split along weakly bonded lipid bilayers. Consequently, the fracture process exposes internal membrane faces rather than either of the membrane’s two external surfaces. During etching, when ice is allowed to sublime after fracturing, limited regions of the actual membrane surfaces are revealed. Examination of the fractured faces and etched surfaces provided strong evidence that biological membranes are organized as lipid bilayers with some proteins on the surface and other proteins extending through the bilayer. Membrane splitting made it possible for electron microscopy to show the relative proportion of a membrane’s area that exists in either of these two organizational modes.
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Simunovic, Mijo, and Patricia Bassereau. "Reshaping biological membranes in endocytosis: crossing the configurational space of membrane-protein interactions." Biological Chemistry 395, no. 3 (March 1, 2014): 275–83. http://dx.doi.org/10.1515/hsz-2013-0242.

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Abstract Lipid membranes are highly dynamic. Over several decades, physicists and biologists have uncovered a number of ways they can change the shape of membranes or alter their phase behavior. In cells, the intricate action of membrane proteins drives these processes. Considering the highly complex ways proteins interact with biological membranes, molecular mechanisms of membrane remodeling still remain unclear. When studying membrane remodeling phenomena, researchers often observe different results, leading them to disparate conclusions on the physiological course of such processes. Here we discuss how combining research methodologies and various experimental conditions contributes to the understanding of the entire phase space of membrane-protein interactions. Using the example of clathrin-mediated endocytosis we try to distinguish the question ‘how can proteins remodel the membrane?’ from ‘how do proteins remodel the membrane in the cell?’ In particular, we consider how altering physical parameters may affect the way membrane is remodeled. Uncovering the full range of physical conditions under which membrane phenomena take place is key in understanding the way cells take advantage of membrane properties in carrying out their vital tasks.
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Epand, Richard M. "Membrane Fusion." Bioscience Reports 20, no. 6 (December 1, 2000): 435–41. http://dx.doi.org/10.1023/a:1010498618600.

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The fusion of biological membranes results in two bilayer-based membranes merging into a single membrane. In this process the lipids have to undergo considerable rearrangement. The nature of the intermediates that are formed during this rearrangement has been investigated. Certain fusion proteins facilitate this process. In many cases short segments of these fusion proteins have a particularly important role in accelerating the fusion process. Studies of the interaction of model peptides with membranes have allowed for increased understanding at the molecular level of the mechanism of the promotion of membrane fusion by fusion proteins. There is an increased appreciation of the roles of several independent segments of fusion proteins in promoting the fusion process. Many of the studies of the fusion of biological membranes have been done with the fusion of enveloped viruses with other membranes. One reason for this is that the number of proteins involved in viral fusion is relatively simple, often requiring only a single protein. For many enveloped viruses, the structure of their fusion proteins has certain common elements, suggesting that they all promote fusion by an analogous mechanism. Some aspects of this mechanism also appears to be common to intracellular fusion, although several proteins are involved in that process which is more complex and regulated than is fusion.
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Zhao, Hongxia, and Pekka Lappalainen. "A simple guide to biochemical approaches for analyzing protein–lipid interactions." Molecular Biology of the Cell 23, no. 15 (August 2012): 2823–30. http://dx.doi.org/10.1091/mbc.e11-07-0645.

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Eukaryotic cells contain many different membrane compartments with characteristic shapes, lipid compositions, and dynamics. A large fraction of cytoplasmic proteins associate with these membrane compartments. Such protein–lipid interactions, which regulate the subcellular localizations and activities of peripheral membrane proteins, are fundamentally important for a variety of cell biological processes ranging from cytoskeletal dynamics and membrane trafficking to intracellular signaling. Reciprocally, many membrane-associated proteins can modulate the shape, lipid composition, and dynamics of cellular membranes. Determining the exact mechanisms by which these proteins interact with membranes will be essential to understanding their biological functions. In this Technical Perspective, we provide a brief introduction to selected biochemical methods that can be applied to study protein–lipid interactions. We also discuss how important it is to choose proper lipid composition, type of model membrane, and biochemical assay to obtain reliable and informative data from the lipid-interaction mechanism of a protein of interest.
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MEREZHINSKAYA, Natasha, Gemma A. J. KUIJPERS, and Yossef RAVIV. "Reversible penetration of α-glutathione S-transferase into biological membranes revealed by photosensitized labelling in situ." Biochemical Journal 335, no. 3 (November 1, 1998): 597–604. http://dx.doi.org/10.1042/bj3350597.

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Fluorescent lipid analogue 3,3´-dioctadecyloxacarbocyanine incorporated into biological membranes was used to induce photoactivation of a hydrophobic probe 5-[125I]iodonaphthyl-1-azide (125INA) by energy transfer and to thereby confine subsequent radiolabelling of proteins to the lipid bilayer. This approach was applied in bovine chromaffin cells to discover cytosolic proteins that reversibly penetrate into membrane domains. α-Glutathione S-transferase (α-GST) was identified as the only labelled protein in bovine chromaffin-cell cytosol, indicating that it inserts reversibly into the membrane lipid bilayer. The selectivity of the labelling towards the lipid bilayer is demonstrated by showing that influenza virus haemagglutinin becomes labelled by 125INA only after the insertion of this protein into the target membrane. The molar 125INA:protein ratio was used as a quantitative criterion for evaluation of the penetration of proteins into the membrane lipid bilayer. This ratio was calculated for four integral membrane proteins and four soluble proteins that interact with biological membranes. The values for four integral membrane proteins (erythrocyte anion transporter, multidrug transporter gp-170, dopamine transporter and fusion-competent influenza virus haemagglutinin) were 1, 8, 2 and 2, respectively, whereas for soluble proteins (annexin VII, protein kinase C, BSA and influenza virus haemagglutinin) the values were 0.002, 0, 0.002 and 0.02, respectively. The molar ratio for α-GST was found to be 1, compatible with the values obtained for integral membrane proteins.
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Luchini, Alessandra, and Giuseppe Vitiello. "Mimicking the Mammalian Plasma Membrane: An Overview of Lipid Membrane Models for Biophysical Studies." Biomimetics 6, no. 1 (December 31, 2020): 3. http://dx.doi.org/10.3390/biomimetics6010003.

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Cell membranes are very complex biological systems including a large variety of lipids and proteins. Therefore, they are difficult to extract and directly investigate with biophysical methods. For many decades, the characterization of simpler biomimetic lipid membranes, which contain only a few lipid species, provided important physico-chemical information on the most abundant lipid species in cell membranes. These studies described physical and chemical properties that are most likely similar to those of real cell membranes. Indeed, biomimetic lipid membranes can be easily prepared in the lab and are compatible with multiple biophysical techniques. Lipid phase transitions, the bilayer structure, the impact of cholesterol on the structure and dynamics of lipid bilayers, and the selective recognition of target lipids by proteins, peptides, and drugs are all examples of the detailed information about cell membranes obtained by the investigation of biomimetic lipid membranes. This review focuses specifically on the advances that were achieved during the last decade in the field of biomimetic lipid membranes mimicking the mammalian plasma membrane. In particular, we provide a description of the most common types of lipid membrane models used for biophysical characterization, i.e., lipid membranes in solution and on surfaces, as well as recent examples of their applications for the investigation of protein-lipid and drug-lipid interactions. Altogether, promising directions for future developments of biomimetic lipid membranes are the further implementation of natural lipid mixtures for the development of more biologically relevant lipid membranes, as well as the development of sample preparation protocols that enable the incorporation of membrane proteins in the biomimetic lipid membranes.
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Jacobs, Miranda L., Margrethe A. Boyd, and Neha P. Kamat. "Diblock copolymers enhance folding of a mechanosensitive membrane protein during cell-free expression." Proceedings of the National Academy of Sciences 116, no. 10 (February 13, 2019): 4031–36. http://dx.doi.org/10.1073/pnas.1814775116.

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The expression and integration of membrane proteins into vesicle membranes is a critical step in the design of cell-mimetic biosensors, bioreactors, and artificial cells. While membrane proteins have been integrated into a variety of nonnatural membranes, the effects of the chemical and physical properties of these vesicle membranes on protein behavior remain largely unknown. Nonnatural amphiphiles, such as diblock copolymers, provide an interface that can be synthetically controlled to better investigate this relationship. Here, we focus on the initial step in a membrane protein’s life cycle: expression and folding. We observe improvements in both the folding and overall production of a model mechanosensitive channel protein, the mechanosensitive channel of large conductance, during cell-free reactions when vesicles containing diblock copolymers are present. By systematically tuning the membrane composition of vesicles through incorporation of a poly(ethylene oxide)-b-poly(butadiene) diblock copolymer, we show that membrane protein folding and production can be improved over that observed in traditional lipid vesicles. We then reproduce this effect with an alternate membrane-elasticizing molecule, C12E8. Our results suggest that global membrane physical properties, specifically available membrane surface area and the membrane area expansion modulus, significantly influence the folding and yield of a membrane protein. Furthermore, our results set the stage for explorations into how nonnatural membrane amphiphiles can be used to both study and enhance the production of biological membrane proteins.
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Lee, Sarah C., and Naomi L. Pollock. "Membrane proteins: is the future disc shaped?" Biochemical Society Transactions 44, no. 4 (August 15, 2016): 1011–18. http://dx.doi.org/10.1042/bst20160015.

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The use of styrene maleic acid lipid particles (SMALPs) for the purification of membrane proteins (MPs) is a rapidly developing technology. The amphiphilic copolymer of styrene and maleic acid (SMA) disrupts biological membranes and can extract membrane proteins in nanodiscs of approximately 10 nm diameter. These discs contain SMA, protein and membrane lipids. There is evidence that MPs in SMALPs retain their native structures and functions, in some cases with enhanced thermal stability. In addition, the method is compatible with biological buffers and a wide variety of biophysical and structural analysis techniques. The use of SMALPs to solubilize and stabilize MPs offers a new approach in our attempts to understand, and influence, the structure and function of MPs and biological membranes. In this review, we critically assess progress with this method, address some of the associated technical challenges, and discuss opportunities for exploiting SMA and SMALPs to expand our understanding of MP biology.
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Dissertations / Theses on the topic "Biological membranes; Membrane proteins"

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Whitehead, L. "Computer simulation of biological membranes and membrane bound proteins." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297412.

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LADHA, PARAG. "POLYMERIC MEMBRANE SUPPORTED BILAYER LIPID MEMBRANES RECONSTITUTED WITH BIOLOGICAL TRANSPORT PROTEINS." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1145901880.

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Boulter, Jonathan Michael. "Structural and functional studies of the erythrocyte anion exchanger, band 3." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297079.

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Dewolf, Christine Elizabeth. "Properties of model biological membranes." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244082.

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Parton, Daniel L. "Pushing the boundaries : molecular dynamics simulations of complex biological membranes." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:7ab91b51-a5ae-46b4-b6dc-3f0dd3f0b477.

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A range of simulations have been conducted to investigate the behaviour of a diverse set of complex biological membrane systems. The processes of interest have required simulations over extended time and length scales, but without sacrifice of molecular detail. For this reason, the primary technique used has been coarse-grained molecular dynamics (CG MD) simulations, in which small groups of atoms are combined into lower-resolution CG particles. The increased computational efficiency of this technique has allowed simulations with time scales of microseconds, and length scales of hundreds of nm. The membrane-permeabilizing action of the antimicrobial peptide maculatin 1.1 was investigated. This short α-helical peptide is thought to kill bacteria by permeabilizing the plasma membrane, but the exact mechanism has not been confirmed. Multiscale (CG and atomistic) simulations show that maculatin can insert into membranes to form disordered, water-permeable aggregates, while CG simulations of large numbers of peptides resulted in substantial deformation of lipid vesicles. The simulations imply that both pore-forming and lytic mechanisms are available to maculatin 1.1, and that the predominance of either depends on conditions such as peptide concentration and membrane composition. A generalized study of membrane protein aggregation was conducted via CG simulations of lipid bilayers containing multiple copies of model transmembrane proteins: either α-helical bundles or β-barrels. By varying the lipid tail length and the membrane type (planar bilayer or spherical vesicle), the simulations display protein aggregation ranging from negligible to extensive; they show how this biologically important process is modulated by hydrophobic mismatch, membrane curvature, and the structural class or orientation of the protein. The association of influenza hemagglutinin (HA) with putative lipid rafts was investigated by simulating aggregates of HA in a domain-forming membrane. The CG MD study addressed an important limitation of model membrane experiments by investigating the influence of high local protein concentration on membrane phase behaviour. The simulations showed attenuated diffusion of unsaturated lipids within HA aggregates, leading to spontaneous accumulation of raft-type lipids (saturated lipids and cholesterol). A CG model of the entire influenza viral envelope was constructed in realistic dimensions, comprising the three types of viral envelope protein (HA, neuraminidase and M2) inserted into a large lipid vesicle. The study represents one of the largest near-atomistic simulations of a biological membrane to date. It shows how the high concentration of proteins found in the viral envelope can attenuate formation of lipid domains, which may help to explain why lipid rafts do not form on large scales in vivo.
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Enders, Oliver. "Structural analysis of biological membranes and proteins by atomic force microscopy." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972570497.

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Moës, Elien. "Theiler's murine encephalomyelitis protein 2C and its effect on membrane trafficking." Thesis, St Andrews, 2008. http://hdl.handle.net/10023/540.

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Rhonemus, Troy A. "Reagents for protein analysis and modification." Virtual Press, 1998. http://liblink.bsu.edu/uhtbin/catkey/1115753.

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Spelbrink, Robert G. "The role of the yeast GRD20 protein in membrane trafficking and actin organization /." free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9974686.

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Millman, Jonathan Scott Andrews David. "Characterization of membrane-binding by FtsY, the prokaryote SRP receptor /." *McMaster only, 2002.

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Books on the topic "Biological membranes; Membrane proteins"

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Dr, Janáček Karel, and Koryta Jiři, eds. Biophysical chemistry of membrane functions. Chichester: Wiley, 1988.

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Society of General Physiologists. Symposium. Cytoskeletal regulation of membrane function: Society of General Physiologists 50th annual symposium, Marine Biological Laboratory, Woods Hole, Massachusetts, 5-7 September 1996. New York: Rockefeller University Press, 1997.

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Frishman, Dmitrij. Structural bioinformatics of membrane proteins. Wien: Springer, 2010.

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Jans, David A. The mobile receptor hypothesis: The role of membrane receptor lateral movement in signal transduction. Austin: R.G. Landes, 1997.

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Tong xing wai mo dan bai zhi sheng wu xin xi xue. Beijing Shi: Guo fang gong ye chu ban she, 2007.

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Channels, carriers, and pumps: An introduction to membrane transport. San Diego: Academic Press, 1990.

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Simon, Sidney A. Current topics in membranes: Mechanosensitive Ion Channels : Part A. Burlington: Elsevier, 2007.

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Winkle, Lon J. Van. Biomembrane transport. San Diego, Calif: Academic Press, 1999.

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Winkle, Lon J. Van. Biomembrane transport. San Diego: Academic Press, 1999.

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Biomembrane transport. San Diego, Calif: Academic, 1999.

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Book chapters on the topic "Biological membranes; Membrane proteins"

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Seaton, Barbara A., and Mary F. Roberts. "Peripheral Membrane Proteins." In Biological Membranes, 355–403. Boston, MA: Birkhäuser Boston, 1996. http://dx.doi.org/10.1007/978-1-4684-8580-6_12.

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Heimburg, Thomas, and Derek Marsh. "Thermodynamics of the Interaction of Proteins with Lipid Membranes." In Biological Membranes, 405–62. Boston, MA: Birkhäuser Boston, 1996. http://dx.doi.org/10.1007/978-1-4684-8580-6_13.

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Démery, Vincent, and David Lacoste. "Mechanical Factors Affecting the Mobility of Membrane Proteins." In Physics of Biological Membranes, 191–211. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-00630-3_8.

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von Heijne, Gunnar. "Assembly of Integral Membrane Proteins." In Biological Membranes: Structure, Biogenesis and Dynamics, 199–205. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-78846-8_19.

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Garland, Peter B., and Pauline Johnson. "Rotational Diffusion of Membrane Proteins Optical Methods." In The Enzymes of Biological Membranes, 421–39. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4684-4598-5_13.

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Hu, Xiche, Dong Xu, Kenneth Hamer, Klaus Schulten, Juergen Koepke, and Hartmut Michel. "Prediction of the Structure of an Integral Membrane Protein: The Light-Harvesting Complex II of Rhodospirillum molischianum." In Biological Membranes, 503–33. Boston, MA: Birkhäuser Boston, 1996. http://dx.doi.org/10.1007/978-1-4684-8580-6_15.

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Williams, R. J. P. "The Nature of Proteins in Membranes." In Recent Advances in Biological Membrane Studies, 17–28. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4684-4979-2_2.

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Wickner, Bill, and Marilyn Rice Leonard. "How do Proteins Cross a Membrane?" In Biological Membranes: Structure, Biogenesis and Dynamics, 207–14. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-78846-8_20.

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Devaux, Philippe F. "Conventional ESR Spectroscopy of Membrane Proteins: Recent Applications." In The Enzymes of Biological Membranes, 259–85. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4684-4598-5_7.

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Watts, Anthony. "Non-Crystallographic Methods to Study Membrane Proteins." In Biological Membranes: Structure, Biogenesis and Dynamics, 131–38. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-78846-8_13.

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Conference papers on the topic "Biological membranes; Membrane proteins"

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Cuppoletti, John. "Composite Synthetic Membranes Containing Native and Engineered Transport Proteins." In ASME 2008 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2008. http://dx.doi.org/10.1115/smasis2008-449.

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Our membrane transport protein laboratory has worked with material scientists, computational chemists and electrical and mechanical engineers to design bioactuators and sensing devices. The group has demonstrated that it is possible to produce materials composed native and engineered biological transport proteins in a variety of synthetic porous and solid materials. Biological transport proteins found in nature include pumps, which use energy to produce gradients of solutes, ion channels, which dissipate ion gradients, and a variety of carriers which can either transport substances down gradients or couple the uphill movement of substances to the dissipation of gradients. More than one type of protein can be reconstituted into the membranes to allow coupling of processes such as forming concentration gradients with ion pumps and dissipating them with an ion channel. Similarly, ion pumps can provide ion gradients to allow the co-transport of another substance. These systems are relevant to bioactuation. An example of a bioactuator that has recently been developed in the laboratory was based on a sucrose-proton exchanger coupled to a proton pump driven by ATP. When coupled together, the net reaction across the synthetic membrane was ATP driven sucrose transport across a flexible membrane across a closed space. As sucrose was transported, net flow of water occurred, causing pressure and deformation of the membrane. Transporters are regulated in nature. These proteins are sensitive to voltage, pH, sensitivity to a large variety of ligands and they can be modified to gain or lose these responses. Examples of sensors include ligand gated ion channels reconstituted on solid and permeable supports. Such sensors have value as high throughput screening devices for drug screening. Other sensors that have been developed in the laboratory include sensors for membrane active bacterial products such as the anthrax pore protein. These materials can be self assembled or manufactured by simple techniques, allowing the components to be stored in a stable form for years before (self) assembly on demand. The components can be modified at the atomic level, and are composed of nanostructures. Ranges of sizes of structures using these components range from the microscopic to macroscopic scale. The transport proteins can be obtained from natural sources or can be produced by recombinant methods from the genomes of all kingdoms including archea, bacteria and eukaryotes. For example, the laboratory is currently studying an ion channel from a thermophile from deep sea vents which has a growth optimum of 90 degrees centigrade, and has membrane transport proteins with very high temperature stability. The transport proteins can also be genetically modified to produce new properties such as activation by different ligands or transport of new substances such as therapeutic agents. The structures of many of these proteins are known, allowing computational chemists to help understand and predict the transport processes and to guide the engineering of new properties for the transport proteins and the composite membranes. Supported by DARPA and USARMY MURI Award and AFOSR.
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Hsieh, Yi-Cheng, Huinan Liang, and Jeffrey D. Zahn. "Microdevices for Microdialysis and Membrane Separations." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-55052.

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Microdialysis is a commonly used technique for separating small biomolecules within a complex biological mixture for continuous biochemical monitoring. Microdialysis is based upon controlling the mass transfer rate of small biomolecules diffusing across a semipermeable membrane into a dialysis fluid while excluding larger molecules such as proteins. These small molecules are subsequently sensed using a biosensor. Since many biosensors are extremely susceptible to fouling, their stability and lifetime can be extended if metabolites are filtered through a microdialysis membrane before the dialysis fluid is moved into the sensor. Dialysis is also used commonly in biological laboratories to desalt high ionic strength protein solutions. As biochemical analysis systems become more integrated for μTAS systems there is a need to automate this process. Thus, an on-chip dialysis system is useful for biochemical reaction engineering where very tight control of ionic conditions must be maintained for effective enzymatic activity. This work demonstrates the ability to integrate polymer microdialysis membranes with microfluidic systems. Microchannels are bonded with a regenerated cellulose membrane. After microchannels are produced using standard processing techniques, they are integrated with these membranes. The cellulose is activated in an oxygen plasma followed by a lamination bond to the microchannels at moderate pressure and elevated temperature. Devices were placed in a solution of rhodamine dye, and dialysis fluid was allowed to flow through the microchannels. The outlet dye concentration was measured by fluorescence intensity as a function of flow rate and follows analytically predicted results.
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Lykotrafitis, George, and He Li. "Two-Component Coarse-Grain Model for Erythrocyte Membrane." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-62133.

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Biological membranes are vital components of living cells as they function to maintain the structural integrity of the cells. Red blood cell (RBC) membrane comprises the lipid bilayer and the cytoskeleton network. The lipid bilayer consists of phospholipids, integral membrane proteins, peripheral proteins and cholesterol. It behaves as a 2D fluid. The cytoskeleton is a network of spectrin tetramers linked at the actin junctions. It is connected to the lipid bilayer primarily via Band-3 and ankyrin proteins. In this paper, we introduce a coarse-grained model with high computational efficiency for simulating a variety of dynamic and topological problems involving erythrocyte membranes. Coarse-grained agents are used to represent a cluster of lipid molecules and proteins with a diameter on the order of lipid bilayer thickness and carry both translational and rotational freedom. The membrane cytoskeleton is modeled as a canonical exagonal network of entropic springs that behave as Worm-Like-Chains (WLC). By simultaneously invoking these characteristics, the proposed model facilitates simulations that span large length-scales (∼ μm) and time-scales (∼ ms). The behavior of the model under shearing at different rates is studied. At low strain rates, the resulted shear stress is mainly due to the spectrin network and it shows the characteristic non-linear behavior of entropic networks, while the viscosity of the fluid-like lipid bilayer contributes to the resulting shear stress at higher strain rates. The apparent ease of this model in combining the spectrin network with the lipid bilayer presents a major advantage over conventional continuum methods such as finite element or finite difference methods for cell membranes.
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Sundaresan, Vishnu-Baba, and Sergio Salinas. "Integrated Bioderived-Conducting Polymer Membrane Nanostructures for Energy Conversion and Storage." In ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-8170.

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Conducting polymers are ionic active materials that can perform electro-chemo-mechanical work through redox reactions. The electro-chemo-mechanical coupling in these materials has been successfully applied to develop various application platforms (actuation systems, sensor elements and energy storage devices (super capacitors, battery electrodes)). Similarly, bioderived membranes are ionic active materials that have been demonstrated as actuators, sensors and energy harvesting devices. Bioderived membranes offer significant advantages over synthetic ionic active materials in energy conversion and the scientific community has put forward various system level concepts for application in engineering applications. The biological origins of these material systems and their subsequent mechanical, electrical and thermal properties have served as a key deterrent in applications. This article proposes a novel architecture that combines a conducting polymer and a bioderived membrane into an integrated material system in which the charge gradients generated from a biochemical reaction is stored and released in the conducting polymer through redox reactions. This paper discusses the fabrication and topographical characterization of the integrated bioderived-conducting polymer membrane nanostructures. The prototype comprises of an organized array of fluid-filled three-dimensional containers with an integrated membrane shell that performs energy conversion and storage owing to its multi-functional microstructure. The bioderived membrane is self-assembled into a hollow spherical container from synthetic membranes or bilayer lipid membranes with proteins and the conducting polymer membrane forms a wrapper around this container resulting in a three-dimensional assembly.
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Maftouni, Negin, Mehriar Amininasab, MohammadReza Ejtehadi, and Farshad Kowsari. "Multiscale Molecular Dynamics Simulation of Nanobio Membrane in Interaction With Protein." In ASME 2013 2nd Global Congress on NanoEngineering for Medicine and Biology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/nemb2013-93054.

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One of the most important biological components is lipid nanobio membrane. The lipid membranes of alive cells and their mechanical properties play an important role in biophysical investigations. Some proteins affect the shape and properties of the nanobio membrane while interacting with it. In this study a multiscale approach is experienced: first a 100ns all atom (fine-grained) molecular dynamics simulation is done to investigate the binding of CTX A3, a protein from snake venom, to a phosphatidylcholine lipid bilayer, second, a 5 micro seconds coarse-grained molecular dynamics simulation is carried out to compute the pressure tensor, lateral pressure, surface tension, and first moment of lateral pressure. Our simulations reveal that the insertion of CTX A3 into one monolayer results in an asymmetrical change in the lateral pressure and distribution of surface tension of the individual bilayer leaflets. The relative variation in the surface tension of the two monolayers as a result of a change in the contribution of the various intermolecular forces may be expressed morphologically and lead to deformation of the lipid membrane.
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Banneyake, B. M. R. U., and Debjyoti Banerjee. "Microfluidic Device for Synthesis of Lipid Bi-Layers." In ASME 2008 Fluids Engineering Division Summer Meeting collocated with the Heat Transfer, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/fedsm2008-55219.

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Lipid bi-layers are ubiquitous components of biological cells — and are found in variety of cell components ranging from cell membranes to membranes of organelles inside the cells. In biological membranes, lipid bi-layer membranes carry membrane proteins, which serve as single channel nanopores that are used to study transport of proteins and characterize the properties of proteins. However, lipid bi-layers have very short half lives, which are usually less than an hour. The lipid bi-layers are usually obtained by physico-chemical interactions between a lipid containing organic solvent, an aqueous buffer solution and a hydrophobic surface. We have developed a continuous flow through microfluidic device using pressure driven flow (by means of a tandem syringe pump system) for synthesis of lipid bi-layers. The microfluidic device consists of two glass substrates with micro-channels and microchambers microfabricated using photolithography and wet glass etching. The microchannels in each substrate is in the form of “+” shape and form a mirror image of each other. A Teflon sheet (∼200 microns thickness) is sandwiched between the glass substrates with a ∼200 microns diameter hole etched in the center to communicate with the two sets of microchannels. A lipid solution in an organic solvent (Pentane) and KCl buffer solution are alternately flown through the legs of the microchannel. The conductivity of the buffer is monitored using a current amplifier. The formation of the lipid bi-layer is confirmed by monitoring the resistivity and the impedance to high frequency electrical oscillations. The flow rate in the microfluidic device is optimized to obtain the lipid bi-layer.
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Taylor, Graham, Donald Leo, and Andy Sarles. "Detection of Botulinum Neurotoxin/A Insertion Using an Encapsulated Interface Bilayer." In ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-8101.

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Many signaling mechanisms in living cells occur at biological boundaries via cell surface receptors and membrane proteins embedded in lipid bilayers. The coordination of actions of sensory and motor neurons in the nervous system represents one example of many that heavily depends on lipid membrane bound receptor mediated signaling. As a result, chemical and biological toxins that disrupt these neural signals can have severe physiological effects, including paralysis and death. Botulinum neurotoxin Type A (BoNT/A) is a proteolytic toxin that inserts through vesicle membranes and cleaves membrane receptors involved with synaptic acetylcholine uptake and nervous system signal conduction. In this work, we investigate the use of a Bioinspired liquid-supported interface bilayer for studying the insertion of BoNT/A toxin molecules into synthetic lipid bilayers. DPhPC lipid bilayers are formed using the regulated attachment method (RAM), as developed by Sarles and Leo, and we perform current measurements on membranes exposed to BoNT/A toxin to characterize activity of toxin interacting with the synthetic bilayer. Control tests without toxin present are also presented. The results of these tests show an increase in the magnitude of current through the bilayer when the toxin is included. We interpret these initial results to mean that incorporation of BoNT/A toxin at a high concentration in an interface bilayer increases the permeability of the membrane as a result of toxin molecules spanning the thickness of the bilayer.
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Freeman, Eric, Lisa Mauck Weiland, and Wilson S. Meng. "Computational Study of Inclusion Burst via the Proton Sponge Hypothesis." In ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2010. http://dx.doi.org/10.1115/smasis2010-3756.

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Biological proteins embedded in either a biological or an engineered membrane will actively maintain electrochemical balance across that membrane through transport of fluid and charge. While membrane studies are often planar, in nature they typically take the form of inclusions (∼spherical). Study and ultimately manipulation of the protein transporter types and density, and interior/exterior states of these inclusions lend insight into burst mechanisms appropriate to a broad array of engineering and biological applications, such as intracellular burst release of a vaccine. To explore these phenomena the governing equations of each transporter, as well as the membrane state are established. The result is a model requiring the simultaneous solution of a stiff system of differential equations. Presented is the computational solution of this system of equations for a specific burst scenario — the hypothesis that a proton sponge may be employed to expedite intracellular burst release of a DNA vaccine is explored.
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Kalyan, N. K., S. G. Lee, W.-T. Hum, R. Hartzell, M. Levner, and P. P. Hung. "IN VITRO STUDIES ON THE BINDING OF TISSUE-TYPE PLASMINOGEN ACTIVATOR (t-PA) AND UROKINASE (u-PA) TO LIVER MEMBRANES." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643603.

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The plasminogen activators, t-PA and u-PA, are glycoproteins known to be involved in homeostasis of the blood clotting system, and thus are of potential clinical use in the treatment of thrombosis. Several in vivo studies have shown that both t-PA and u-PA are quickly removed from the blood circulation, predominantly by the liver. The mechanism by which the liver removes these proteins is not understood. To delineate this, we conducted in vitro studies of binding of PAs or their derivatives to isolated mouse liver membranes utilizing a functional assay developed in our laboratory. The assay consisted of initial binding of t-PA to liver membranes followed by centrifugation to pellet the membranes and the assay of the activity of the membrane-bound t-PA by a fibrin-agar plate method. The bound t-PA, which retained complete enzymic activity, could be dissociated by SDS treatment in an undegraded form as shown by SDS-PAGE. The binding of t-PA as well as u-PA was very fast and did not compete with glycoproteins or sugars containing the terminal galactose, mannose and N-acetylglucosamine residues. Furthermore, the treatment of t-PA with neuraminidase and/or periodate oxidation did not affect its binding characteristics. These data suggest that the carbohydrate moieties of t-PA and u-PA, unlike many glycoproteins, do not mediate their binding to the liver. This raised the possibility of the liver binding sequence being located in the protein backbone, especially the non-protease domains which are known to determine the biological specificities of PAs. The relative binding of u-PA and its low molecular weight (LMW) derivative containing only the protease domain, to the liver membranes was studied. Unlike u-PA and t-PA, LMW-urokinase did not bind significantly. This suggests that the protein sequence containing the non-protease domains, rather than the carbohydrate moieties of PAs contain the information necessary for binding to the liver and possibly their clearance from the blood circulation.
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Hack, N., J. M. Wilkinson, and N. Crawford. "A MONOCLONAL ANTIBODY (PL/IM 430) THAT BLOCKS THE ACTIVE TRANSL0CATI0N OF Ca2+ INTO HUMAN PLATELET INTRACELLULAR MEMBRANE (ER) VESICLES." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644678.

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In earlier studies [1] we identified a number of important biological properties associated with highly purified human platelet intracellular membrane (ER), isolated by continuous flow electrophoresis. These included a high affinity Ca2+Mg2+ ATPase and protein phosghorylation both of which are involved inthe active uptake of Ca into ER vesicles. The stored Ca2+ could be released with inositol(1,4,5)trisphosphate, (IP ), (approx. 50% release in 30 s 1/2 max. for release - 0.253 μM IP3,) [2]. To probe the structure-function relationship of proteins in these ER vesicles, a panel of monoclonal antibodies (Mabs) has been raised, using the ER membrane preparation as immunogen. Four of these Mabs recognise a single 100 kDa polypeptide by immunoblotting. This protein is present in platelet membranes and can also be identified in cultured human monocyte, macrophage and endothelial cell lines. None of the M^bs showed any significant effect upon the ER membrane Ca2+ Mg2+ ATPase activity but one, PL/IM 430 (of IgGl subclass), inhibited the Ca2+sequestration by the vesicles significantly (approx. 70% inhibition at 10 μM IgG). This inhibition was independent of the ATP concentration over a range2of 0-2 mM ATP, but was2dose-dependent for external free Ca 2between 30-300 nM Ca2+, giving maximum inhibition at 300 nM Ca with 10 pM IgG2+ Binding of the antibody substantially lowers the Vmax for Ca2+for Ca2+ uptake but is without effect upon the Km. PL/IM 430 therefore appears to recognise a 100 kDa polypeptide closely involved with Ca2+ trnslocation but at a site which i, s without effect upon the Ca2+Mg− ATPase associated with the Ca pump.We are grateful to the Wellcome Trust and the British Heart Foundation for financial support for these studies.[1] Hack, N., Croset, M. and Crawford, N. (1986) Biochem. J. 233, 661-668.[2] Authi, K. S. and Crawford, N. (1985) Biochem. J. Z3O, 247-253
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