Protein , association interfaces

In the insulin-L/CL complexes, it is evident from the dimensions of the lamellar liquid crystalline phase that insulin is simply associated electrostatically with the L/CL bilayer and that it replaces water (13). The amounts depend on the number of charges (see Figure 8). The limit of protein association is reached when no more surface is available at the bilayer-water interface. 

Hygroscopic Substance. Perhaps the most distinctive and vitally important surface property of SC is its capacity to absorb up to six times its own weight in water (16, 89, 90). Attempts have been made to associate this property with protein surfaces (20, 91), protein-lipid interfaces (38, 63, 66), or with lipids alone (66, 92). Recently, investigators have emphasized the joint importance of lipids and proteins, or proteoglycan complexes, in hygroscopic properties (16, 66, 92). 

Thus, the overall free energy change AG associated with creating the protein-water interface by transferring the water molecules from the bulk to the interface is... 

In the mixed systems, the behavior was similar to that observed for surface pressure. In the presence of surface-active PGA (Figure 25.3a and b) at low concentrations in the bulk phase (0.1 wt%), competition between the biopolymers at the interface results in a lower Ed than that expected from the observation of the single components. However, at higher concentrations of PS and long adsorption times, a cooperative adsorption can be deduced. This result could be explained by a concentration of (3-lg at the interface caused by the incompatibility with different biopolymers (that is more evident at higher concentrations). These phenomena would lead to an increase in the protein association in the film with the resultant increase in viscoelasticity. 

The enzyme associates with the peroxisomal membrane." Several positive residues create an electropositive patch on the surface of the protein" that could bind with the negatively charged heads of membrane lipids. The release of fatty acid product and the entrance of the fatty alcohol substrate is proposed to occur at the protein-membrane interface because residues in the gating helix contribute to the membrane-binding positive patch. 

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