Lipid/protein bilayer

Biosensors based on membrane receptors require the protein to be coupled both functionally and structurally with electrical substrates. The interface between the biological recognition element and the solid substrate must allow electrical signal transduction and provide an environment conducive to biological function. Both requirements are demanding. A significant barrier to production of this type of sensor has been the tremendous difficulty of preparing functional and stable lipid-protein bilayer membranes linked to... 

T. Schiirholz and H. Schindler, Formation of lipid-protein bilayers by micropipette guided contact of two monolayers, FEES Letters 152(2), 187-190, (1983). doi 10.1016/0014-5793(83)80376-7... 

Baumgartner and coworkers [145,146] study lipid-protein interactions in lipid bilayers. The lipids are modeled as chains of hard spheres with heads tethered to two virtual surfaces, representing the two sides of the bilayer. Within this model, Baumgartner [145] has investigated the influence of membrane curvature on the conformations of a long embedded chain (a protein ). He predicts that the protein spontaneously localizes on the inner side of the membrane, due to the larger fluctuations of lipid density there. Sintes and Baumgartner [146] have calculated the lipid-mediated interactions between cylindrical inclusions ( proteins ). Apart from the... 

Rytdmaa, M., and Kinnunen, P.K.J., 1995, ReversibUity of the binding of cytochrome c to Uposomes. Implications for lipid-protein interactions./. B/oZ. Chem., 270 3197-3202 Salamon, Z., and ToUin, G., 1996, Surface plasmon resonance studies of complex formation between cytochrome c and bovine cytochrome c oxidase incorporated into a supported planar Upid bUayer. II. Binding of cytochrome c to oxidase-containing cardiohpin /phosphatidylcholine membranes. Biophys. J., 71 858-867 Salamon, Z., and ToUin, G., 1997, Interaction ofhorse heart cytochrome c with Upid bilayer membranes effects on redox potentials. J. Bioenerg. Biomembr. 29 211-221 Scarlett, J.L., and Murphy, M.P., 1997, Release of apoptogenic proteins from the... 

Natural biological membranes consist of lipid bilayers, which typically comprise a complex mixture of phospholipids and sterol, along with embedded or surface associated proteins. The sterol cholesterol is an important component of animal cell membranes, which may consist of up to 50 mol% cholesterol. As cholesterol can significantly modify the bilayer physical properties, such as acyl-chain orientational order, model membranes containing cholesterol have been studied extensively. Spectroscopic and diffraction experiments reveal that cholesterol in a lipid-crystalline bilayer increases the orientational order of the lipid acyl-chains without substantially restricting the mobility of the lipid molecules. Cholesterol thickens a liquid-crystalline bilayer and increases the packing density of lipid acyl-chains in the plane of the bilayer in a way that has been referred to as a condensing effect. 

A retrovirus consists of double-stranded RNA (the genome) and a few proteins within a lipid envelope bilayer and... 

All biological membranes are constructed according to a standard pattern. They consist of a continuous bilayer of amphipathic lipids approximately 5 nm thick, into which proteins are embedded, in addition, some membranes also carry carbohydrates (mono- and oligosaccharides) on their exterior, which are bound to lipids and proteins. The proportions of lipids, proteins, and carbohydrates differ markedly depending on the type of cell and membrane (see p. 216). 

Often the cell accomphshes the association of signal proteins with the membrane by post-translationaUy affixed lipid anchors composed of hydrophobic residues, such as fatty acids, isoprenoids or complex glycolipids (see fig. 3.11). These lipid moieties of lipidated proteins favor membrane association by inserting themselves into the phospholipid bilayer. 

The structure of biological and model membranes is frequently viewed in the context of the fluid mosaic model [4], Since biological membranes are composed of a mixture of various lipids, proteins, and carbohydrates the supra-structure or lateral organization of the components is not necessarily random. In order to model biological membranes, lipid assemblies of increasing complexity were studied. Extensive investigation of multicomponent monolayers (at the air-water interface) as well as bilayers have been reported. 

Absorption is necessary for the chemical to exert a systemic biological/toxic effect and involves crossing membranes. Membranes are semipermeable phospholipid/protein bilayers. The phospholipids and proteins are of variable structure, and the membrane is selectively permeable. The physicochemical characteristics of foreign molecules that are important include size/shape, lipid solubility, structure, and charge/polarity. 

The low lipid-protein ratio of 0.5 together with the size of the sarcoplasmic vesicles implies that only approximately 30% of their membranes can be occupied by a regular lipid bilayer structure. Consequently, a large fraction of the membrane protein must interrupt the lipid bilayer and reach throughlt. The fact that only one polypeptide chain constitutes the structural unit of the calcium transport protein strong-... 

During the 1960s, various alternatives to the Davson-Danielli model were proposed. Some investigators abandoned the idea of a phospholipid bilayer and suggested instead that membranes consist of aggregates of lipid-protein complexes. However, in 1972, Jon Singer and Garth Nicol-... 

The possibility of obtaining information about lipid-protein interaction makes Raman spectroscopy a useful technique for structural studies of membranes. As an illustration of spectra recorded from biological samples, see the Raman spectrum of a frog sciatic nerve in Figure 11. The C-H stretching vibration region is characteristic of lipid bilayers in a... 

Although numerous models for the structure of membranes have been proposed, the structural features which are generally accepted at present are rather similar to the original Danielli-Davson model. There is convincing evidence that the structure is dominated by lipid bilayers. The state of order of the hydrocarbon chains is now being studied extensively by many groups (see below). Less is known about the proteins. Besides the proteins that are located on the outside according to the Danielli-Davson model, there are also proteins that are partly buried in the hydro-phobic interior of the lipid layer however, little is known about the lipid-protein interaction. 

Sanders, C.R.I., and G.C. Landis (1995) Reconstitution of membrane proteins into lipid-rich bilayered mixed micelles for NMR studies. Biochemistry 34,4030-4040. 

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