Energy of hydrophobic interaction

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,... 

Molecular descriptors based on hydrophobic interaction energy between nonpolar surfaces of ligand and receptor. The energy of hydrophobic interactions derives from the disruption of the water structme around nonpolar surfaces resulting in a gain of entropy [Abraham and Kellogg, 1993]. 

Numerous studies have been designed to reveal the entropy and energy of hydrophobic interactions. The simplest approach used in these studies is to investigate the temperature dependence of aggregation in finite-concentration solutions. Skipper reported the first such calculation on methane solutions. Fie observed that aggregation became more favorable as T was increased, indicating that the process is endothermic. Interpretation of this type of study is obfuscated by the contribution of many-body solute-solute effects, however. Smith and co-workers reported the first calculations of the entropy and the... 

Internal Energy of Hydrophobic Interactions Computer Simulations. 

The free energy of hydrophobic interaction, AGh<, is the sum of several contributions, the free energy corresponding to the structural change of water (AGw) and the free energy corresponding to the change of states of the side chains (AGs) ... 

The character of hydrophobic interactions is revealed by their temperature dependence. At low temperature, their stability increases in temperature, contrary to what is observed for hydrogen bonds (Nemethy and Scheraga, 1962a,b,c, Nemethy et aU 1963 Scheraga et al, 1962). The variation of free energy of hydrophobic interactions as a function of temperature is described by the following equation ... 

Solute adsorption can be minimized most effectively by capillary wall coating, thereby decreasing the free energy of hydrophobic or ionic interactions. Coating can be achieved either by covalently bonded organic modifiers, e.g., polyacrylamides, sulfonic acids, polyethylene glycols, maltose, and polyvinyl pyrolidinone, or by dynamic deactivation (i.e., addition of... 

As mentioned earlier, proteins are subject to cold denaturation because they exhibit maximal stability at temperatures greater than 0°C. The basis of this effect is the reduction in the stabilizing influence of hydrophobic interactions as temperature is reduced. Recall that the burial of hydrophobic side-chains in the folded protein is favored by entropy considerations (AS is positive), but that the enthalpy change associated with these burials is unfavorable (AH, too, is positive). Thus, as temperature decreases, there is less energy available to remove water from around hydrophobic groups in contact with the solvent. Furthermore, as temperature is reduced, the term [— TAS] takes on a smaller absolute value. For these reasons, the contribution of the hydrophobic effect to the net free energy of stabilization of a protein is reduced at low temperatures, and cold-induced unfolding of proteins (cold denaturation) may occur. 

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