Phospholipid bilayer diagram

Fig. 20. Diagram showing a singlelength channel and a doublelength channel formed across a phospholipid bilayer by a circular cluster of nystatin or amphotericin B aggregates...

Fig. 10.5 Schematic diagrams a micelle consisting of ionized fatty acid molecules, a phospholipid bilayer and the vesicle bilayer of a liposome...

Phospholipid(s) 379, 380,382 - 387, 392. See also Specific substances bilayer diagram 391 head groups, functions of 396 inverted hexagonal phase 397 31P NMR 397 non-bilayer structures 397 Phosphomannomutase 654 Phosphomutases 526 Phosphonamidate 626s... 

FIGURE 6.1. Schematic diagram of a supported phospholipid bilayer membrane containing a covalently attached ligand molecule. 

Figure 3. Schematic representation of a phospholipid-water phase diagram. The temperature scale is arbitrary and varies from lipid to lipid. For the sake of clarity phase separations and other complexities in the 20-99% water region are not indicated. Structures proposed for the phospholipid bilayers at different temperatures are shown on the right-hand side. At low temperature, the lipids are arranged in tilted one-dimensional lattices. At the pre-transition temperature, two-dimensional arrangements are formed with periodic undulations. Above the main phase, transitions lipids revert to one-dimensional lattice arrangements, separated somewhat from each other, and assume mobile liquid-like conformations.

Fig. 6. r,/7-phase diagram for the main (chain-melting) transition of different phospholipid bilayer systems. The fluid (liquid-crystalline) L -phase is observed in the low-pressure, high-temperature region of the phase diagram. 

A condensed soft matter system like the phospholipid bilayer exhibits complex dynamic behavior that is strongly dependent upon composition and temperature. The thermal behavior of phosphohpid bilayers can be understood using simplified phase diagrams that correlate temperature and membrane composition. For typical mixtures of phosphatidylcholines with cholesterol three important phases exist over physiologically relevant temperatures (Figure 2a).Pure phosphatidylcholine bilayers will form a gel phase at low temperatures, which is often called the solid ordered (So) or phase. It is characterized by low lateral mobility of the lipids and strong interactions between lipids in the bilayer (diffusion rates of cm s ). ... 

Addition of 50 mol% cholesterol to selectively deuterated DPPC bilayers leads to an elimination of the gel-to-liquid crystal phase transition at 41 °C. In contrast, cholesterol is also found to enhance the tendency of the PC components to exhibit lateral segregation. These seemingly contradictory effects of cholesterol can be readily explained in light of the cholesterol-phospholipid phase diagrams. 

Figure 41-5. Diagram of a section of a bilayer membrane formed from phospholipid molecules. The unsaturated fatty acid tails are kinked and lead to more spacing between the polar head groups, hence to more room for movement. This in turn results in increased membrane fluidity. (Slightly modified and reproduced, with permission, from Stryer L Biochemistry, 2nd ed. Freeman, 1981.)...

Liposomes have been, and continue to be, of considerable interest in drug-delivery systems. A schematic diagram of their production is shown in Fig. 10. Liposomes are normally composed of phospholipids that spontaneously form multilamellar, concentric, bilayer vesicles, with layers of aqueous media separating the lipid layers. These systems, commonly referred to as multilamellar vesicles (MLVs), have diameters in the range of 15 pm. Sonication of MLVs... 

Figure19.1 A schematic diagram of a plasma membrane. Integral proteins are embedded in a bilayer composed of phospholipids (shown, for clarity, in much greater proportion than they have in biological membranes) and cholesterol. The carbohydrate components of glycoproteins and glycolipids occur only on the external face of the membrane. (Reproduced from D. Voet and J. G. Voet, Biochemistry, 3rd edn, 2004. 2004, Donald and Judith G Voet. Reprinted with permission of John Wiley and Sons, Inc.)...

MICELLAR SUBSTRATES. Phospholipids in micelles are frequently found to be more active substrates in lipolysis than those phospholipids residing in a lipid bilayer". Dennis first described the use of Triton X-100 to manipulate the amount of phospholipid per unit surface area of a micelle in a systematic analysis of the interfacial interactions of lipases with lipid micelles. Verger and Jain et al have presented cogent accounts of the kinetics of interfacial catalysis by phospholipases. The complexity of the problem is illustrated in the diagram shown in Fig. 2 showing how the enzyme in the aqueous phase can bind to the interface (designated by the asterisk) and then become activated. Once this is achieved, E catalyzes conversion of S to release P. ... 

Figure 18-8 Stereoscopic ribbon diagrams of the chicken bc1 complex (A) The native dimer. The molecular twofold axis runs vertically between the two monomers. Quinones, phospholipids, and detergent molecules are not shown for clarity. The presumed membrane bilayer is represented by a gray band. (B) Isolated close-up view of the two conformations of the Rieske protein (top and long helix at right) in contact with cytochrome b (below), with associated heme groups and bound inhibitors, stigmatellin, and antimycin. The isolated heme of cytochrome c, (left, above) is also shown. (C) Structure of the intermembrane (external surface) domains of the chicken bcx complex. This is viewed from within the membrane, with the transmembrane helices truncated at roughly the membrane surface. Ball-and-stick models represent the heme group of cytochrome cy the Rieske iron-sulfur cluster, and the disulfide cysteines of subunit 8. SU, subunit cyt, cytochrome. From Zhang et al.105...

To estimate the percentage of the surface covered by phospholipid, you would need to know (or estimate) the average cross-sectional area of a phospholipid in a bilayer (which you might learn from an experiment such as that diagrammed in Problem 1, above) and the average cross-sectional area of a 50 kDa protein. 

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