Hydrophobic interaction, free energy

Fig. 1.4. Paramagnetic relaxation enhancement profiles for apomyoglobin unfolded at pH 2.3 with spin labels at the positions indicated by the arrows. The fitted, curves show the initial (pale gray) fits and the fits obtained after correction for differences in pairwise cluster interaction free energies (dark gray lines).The location of hydrophobic clusters defined from regions of high AABUF are indicated by bars at the top of the figure. Reproduced with permission from [17]...

The explanation of the hydrophobic effect and the resulting hydrophobic bonding is still a matter of some dispute. For instance, attraction due to dispersion forces may provide a considerable part of the interaction free energy of a hydrophobic bond, varying with the chemical constitution of the groups involved. 

As with SCRF-PCM only macroscopic electrostatic contribntions to the Gibbs free energy of solvation are taken into account, short-range effects which are limited predominantly to the first solvation shell have to be considered by adding additional tenns. These correct for the neglect of effects caused by solnte-solvent electron correlation inclnding dispersion forces, hydrophobic interactions, dielectric saturation in the case of... 

D. E. Smith and A. D. J. Haymet. Free energy, entropy and internal energy of hydrophobic interactions computer simulations. J. Chem. P/iys., 98 6445-6454,... 

Several different kinds of noncovalent interactions are of vital importance in protein structure. Hydrogen bonds, hydrophobic interactions, electrostatic bonds, and van der Waals forces are all noncovalent in nature, yet are extremely important influences on protein conformations. The stabilization free energies afforded by each of these interactions may be highly dependent on the local environment within the protein, but certain generalizations can still be made. 

Separations in hydrophobic interaction chromatography have been modeled as a function of the ionic strength of the buffer and of the hydrophobicity of the column, and tested using the elution of lysozyme and ovalbumin from octyl-, butyl- and phenyl-Sepharose phases.2 The theoretical framework used preferential interaction analysis, a theory competitive to solvophobic theory. Solvophobic theory views protein-surface interaction as a two-step process. In this model, the protein appears in a cavity in the water formed above the adsorption site and then adsorbs to the phase, with the free energy change... 

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