Acyl chains hydrophobic

Capryl derivatives proved to be efficient corrosion inhibitors. This indicates the sig-niricance of the hydrophobic side chain in the acyl moiety. It is likely that in the case of a shorter (C2-C6) acyl chain, hydrophobic bulkiness of the chemicals would probably not be sufficient to cover the metal surface as an insulator layer (Telegdi et al., 1995). C10 derivatives are effective the carboxyl group faces the metal surface and, similar to a micelle, the alkyl chains are at an appropriate angle to the iron and will save the metal from attack by aggressive ions in aqueous solution. 

The anthroyl fluorophore is located deep in the hydrophobic region of the lipid bilayer corresponding to the C9-C16 segment of the acyl chains. The excited-state lifetime, associated with a non-structured fluorescence spectrum with a maximum at 460 nm (to be compared to those shown in Figure 7.6), can be accounted for by interaction of the fluorophore with water molecules that diffuse across the bilayer. Information is thus obtained on the permeability of lipid bilayers to water and its modulation by cholesterol. 

Our proposed mechanism is outlined in Figure 6, with a tentative assumption that once the acyl chains of cardiolipin are peroxidized, their hydrophobicity will diminish and a resulting conformational change cannot be accommodated within the cavity between the heme plane and the iimer surface of cytochrome c. 

Several studies have dealt with the influence of lipids on conformational equilibria in cytochrome c via hydrophobic and electrostatic interactions. The binding of sodium dodecyl sulfate monomers and micelles was reported to cause a transition of cytochrome c to a state B2 which is of potential physiological relevance. The interplay between heme only state changes and secondary structure changes was analyzed by freeze-quench and stopped-flow experiments.276 The response of the heme spin state to lipid acyl chains in cytochrome c was... 

FIGURE 11-3 Fluid mosaic model for membrane structure. The fatty acyl chains in the interior of the membrane form a fluid, hydrophobic region. Integral proteins float in this sea of lipid, held by hydrophobic interactions with their nonpolar amino acid side chains. Both proteins and lipids are free to move laterally in the plane of the... 

Membranes are composed of lipids and proteins in varying combinations particular to each species, cell type, and organelle. The fluid mosaic model describes features common to all biological membranes. The lipid bilayer is the basic structural unit. Fatty acyl chains of phospholipids and the steroid nucleus of sterols are oriented toward the interior of the bilayer their hydrophobic interactions stabilize the bilayer but give it flexibility. 

The location of the acyl chain is of primary importance in the binding process because of its size. Due to the movement of lid during interfacial activation, a hydrophobic trench is created between the lid and enzyme surface. The trench size is ideal to accommodate the acyl chain. Interactions between the non-polar residues of the trench and the non-polar acyl chain stabilize the coupling. It has been postulated that the configuration of the trench is responsible for substrate specificity. This hypothesis seems plausible since lipases usually discriminate against certain acyl chain lengths, degrees of unsaturation, and location of double bonds in the chain. Any of these factors could affect the interaction between the acyl chain and the trench. 

The looping around of photoactivated fatty acyl chains to the membrane surface, with subsequent reaction there or at an intervening point, is a distinct possibility (Bayley and Knowles, 1978a). Such events would be analogous to the exchange of simple hydrophobic reagents into the aqueous phase resulting in the derivatization of peripheral proteins, but in the case... 

Fluorescence probes are frequently used to study changes in membrane organization and membrane fluidity induced by anesthetics, various drags, and insecticides. This technique measures fluidity as the rate and extent of phospholipid acyl chain excursion away from some initial chain orientation during the lifetime of the excited fluorescence state. Special techniques even allow the place of interaction to be localized, i.e. to the outer membrane region, the hydrophobic area, or the embedded proteins. 

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