Nonpolar interactions, effect

Many substances do not dissolve in water. Pure water will not, for example, dissolve animal fat, because fat molecules are nonpolar and do not interact effectively with polar water molecules. In general, polar and ionic substances are expected to be more soluble in water than nonpolar substances. 

The polar ethanol and the nonpolar hexane molecules are not able to interact effectively. Thus the enthalpy of solution is positive, as is the deviation from Raoult s law. 

Hydrophobic interaction chromatography (HIC) is a method in which proteins in a high salt environment interact hydrophobically with nonpolar ligands. Effective salts are antichaotropic, meaning that they promote the ordering of water molecules at surfaces. Se-... 

In both cases, g depends simultaneously on the expansion factor % T) or (T) and on 2. The two effects are difficult to separate as very little is known about the expansion coefficients. Moreover if (jT) is equal to unity in all nonpolar solvents as it seems to be the case for polybutyl methacrylate dissolved in benzene and in carbon tetrachloride, the expansion observed in polar solvents may be due entirely to an interaction effect, so that f (T) and 2 are probably not independent of one another. More experimental work is necessary to confirm these views. As has already been said, comparison of the influence of various... 

GB/S A Generalized-Born/Surface-Area. A method for simulating solvation implicitly, developed by W.C. Still s group at Columbia University. The solute-solvent electrostatic polarization is computed using the Generalized-Born equation. Nonpolar solvation effects such as solvent-solvent cavity formation and solute-solvent van der Waals interactions are computed using atomic solvation parameters, which are based on the solvent accessible surface area. Both water and chloroform solvation can be emulated. 

Several structural factors have been considered as possible causes of the anomeric effect. In localized valence bond terminology, there is a larger dipole-dipole repulsion between the polar bonds at the anomeric carbon in the equatorial conformation This dipole-dipole interaction is reduced in the axial conformation and this factor contributes to the solvent dependence of the anomeric effect. The preference for the axial orientation is highest in nonpolar solvent effects, where the effect of dipolar... 

Of equal importance, the use of RPC and HIC techniques provides a very powerful avenue to explore the molecular basis of the hydrophobic effect per se that these biomacromolecules exhibit. Since the time of the initial attempts, commencing over 50 years ago, to exploit the hydrophobic effect as part of robust separation procedures, RPC and HIC have thus come to assume a dominant position for the isolation and analysis of many proteins and now represent the techniques par excellence for the purification and analysis of polypeptides prepared by solid- or solution-phase synthetic procedures. Equally, these techniques provide an opportunity to explore the role of the hydrophobic effect in the stabilization and folding of proteins and polypeptides, the molecular forces that are involved in these processes, the thermodynamics of their interaction with relatively well-defined nonpolar surfaces, and the biophysics of peptide or protein nonpolar interactions in general. 

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