Hydrophobic bonding parameter

The coefficients of tt in Equations (66) and (67) indicate that the hydrophobic bonding parameter contributes little to the inhibiting activity and this is confirmed by the low correlation coefficient in Equation (66). The electronic contribution is not likely to be important since the correlation coefficient in Equation (65) is low, and the improvement in the correlation coefficient in moving from Equation (64) to (67) is very small. The predominant effect is therefore steric, confirmed by the high correlation coefficients of the equations E (p. 1 %). 

With alkali halide-TBA-W or alkali halide-PD-W systems, the parameters Bne are negative for volumes and heat capacities (see Figures 1-5 and 10). This sign seems to be the one usually observed for the interaction of a hydrophobic with a hydrophilic solute (6). At intermediate cosolvent concentration, AYe°(W — W + TBA) and AYe°(W — W + PD) deviate in the direction we would expect for hydrophobic association the volume increases sharply, and the heat capacity decreases further. Inorganic electrolytes lower the critical micelle concentration of surfactants by salting out the monomers, thus favoring micellization (25) in a similar way, in the co-sphere of a hydrophilic ion, the hydrophobic bonding between the cosolvent molecules may be enhanced. 

T is the defining parameter of both the thermodynamic and kinetic states of polysaccharide dispersions. With declining T, T increases and vf decreases until Vj = 0 when all macromolecular motion ceases and the dispersion becomes essentially frozen with the onset of brittleness. With increases in T, the hydrogen-bond strength decreases, a poor solvent may become good, and a good solvent may become better. The strength of the hydrophobic bond increases with T (Ben-Naim, 1980). 

Improvements of the Pohtzer hydrophobic model were later proposed using additional quantum-chemical descriptors derived from the molecular electrostatic potential, dipole moment, and ionization energies. These descriptors were searched for to give the best estimations of the cavity term, polarity/dipolarizability term, and hydrogen-bond parameters defined in -> linear solvation energy relationships [Haeberlein and Brinck, 1997]. 

In a detailed structure-activity study Gil and Wilkinson (1977) found that of 47 substituted 1,2,3-benzothiodiazoles the 6-butyI derivative 19 is the most active inhibitor of microsomal oxidation. Regression analyses have shown that the activity of the S-, 6- and 3,6-substituted compounds can be satisfactorily described in terms of the hydrophobic bonding constant n and the Hammett constant r whereas that of the 4-substituted derivatives depend on n and the Taft s steric parameter ,. 

The actions of the two chondroitinases AC have been compared via steady-state kinetics carried out at pH 6.0. The Arthrobacter enzyme was susceptible to salt activation/regression and bivalent metal ions such as Ca +, Co +, Mg +, and Ba + were more effective for activation than virulent ions such as Na+ and K+. Various kinetic parameters of the actions of the enzymes was determined and thermodynamic parameters were calculated. The results obtained suggested that the driving force of enzyme-substrate complex formation could be attributed to ionic interaction for Arthrobacter chondroitinase AC and to hydrophobic bonding for Flavobacterium chondroitinase AC. 

As noted above, surfactant adsorption may be described in terms of simple interaction parameters. However, in some cases these interaction parameters may involve ill-defined forces, such as hydrophobic bonding, solvation forces and chemisorption. In addition, the adsorption of ionic surfactants involves electrostatic forces, particularly with polar surfaces containing ionogenic groups. Thus, the adsorption of ionic and nonionic surfactants will be treated separately. Surfaces (substrates) can be also hydrophobic or hydrophilic and these may be treated separately. 

H hydrophobic interaction parameter 5 steric selectivity parameter A H-bond donor (acidity) parameter B H-bond acceptor (basicity) parameter C cation-exchange parameter (at dissociated silanols)... 

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