Hydrophobic interchange

The structures predicted for the fast and slow Ca -ATPase (Fig. 1) are 84 /o identical [8], There are 164 differences in the amino acid sequences between the two isoenzymes, 66 of which are conservative replacements, involving substitution of serine for threonine, aspartic for glutamic, lysine for arginine, or interchanges between aromatic or hydrophobic amino acids [8],... 

A comparahve analysis of coefficients and descriptors clarifies the relationship between lipophilicity and hydrophobicity (Y in Eq. 4 is the molar volume which assesses the solute s capacity to elicit nonpolar interactions (i.e. hydrophobic forces) which, as also clearly stated in the International Union of Pure and Applied Chemistry definitions [3] are not synonyms but, when only neutral species are concerned, may be considered as interchangeable. In the majority of partitioning systems, the lipophilicity is chiefly due to the hydrophobicity, as is clearly indicated by the finding that the product of numerical values of the descriptors V and of the coefficient v is larger in absolute value than the corresponding product of other couples of descriptors/coefficients [9]. This explains the very common linear rela-... 

Bioadhesion to the vaginal substrate implies knowledge and demonstration of the mechanism of interaction. In the present case, mucoadhesion, bioadhesion, and substantivity can be used interchangeably when evaluating the mucosa as a substrate. Several forces may be active, such as electrostatic, hydrophobic, and hydrogen bonding, giving rise to surface interactions between the polymer and the mucosal substrate or diffusion into the mucus layer [48,49]. 

STEREOCHEMICAL TERMINOLOGY, lUPAC RECOMMENDATIONS Apical and equatorial ligand interchange, PSEUDOROTATION APICOPHILIOITY APOACTIVATOR Apolar side-chain interactions, HYDROPHOBIC EFFECT Apparent equilibrium constant,... 

Catsimpoolas et al. (2) and Hermansson ( ) have found that the reaction leading to formation of the soluble aggregates is reversible. Recently, Takagi et al. ( ) found that hydrophobic interactions are primarily responsible for the formation of the soluble aggregates which are subsequently irreversibly insolu-bilized through intermolecular disulfide bond interchange. 

There is another phenomenon, regarded as a deteriorative change in the protein of soy milk, caused also by the evaporation of water. This is a film formation on the surface of soy milk, which occurs when heated soy milk is kept open to the air. This phenomenon is observed not only in heated soy milk but also in heated cow s milk. Film formation of soy milk occurs only when the soy milk is heated above 60°C and there is evaporation of water from the surface of the soy milk. The mechanism of protein insolubilization is basically the same as that of soy milk powder produced from heated soy milk (10. When water is removed from the surface of heated soy milk by evaporation, the molecular concentration of protein near the surface increases locally and the exposed reactive groups of the denatured molecules come close enough to interact intermolecularly both by hydrophobic interactions and through the sulfhydryl/disulfide interchange reaction to form a polymerization (film) on the surface. The upper side of the film contains more hydrophobic amino acids because of orientation of the hydrophobic portions of the unfolded molecules to the atmosphere rather than into the aqueous solution. 

Denaturation of whey proteins has been shown to unfold their polypeptide chains and convert thexx conformation from a globular to an extended form that facilitates their self interaction (aggregation) and interaction with K-casein by disulfide interchange, ionic and hydrophobic bonding (4). 

Throughout the discussion, the terms surface active agent, surfactant, and detergent are used interchangeably to refer to amphiphilic substances which form association colloids or micelles in solution. Amphiphilic substances or amphiphiles are molecules possessing distinct regions of hydrophobic and hydrophilic character. 

It is therefore understandable that the aminotriazole- or BrCN-modified enzyme no longer participates in ligand interchange reactions, particularly if, as implied, YH acts as a general acid-base catalyst. That HA rather than Ar is the reactive species may therefore indicate that the distal site, embedded in a hydrophobic environment, is largely inaccessible to anions and cations. 

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