Preferential solvation of biomolecules

This cannot be interpreted in terms of PS. Because of the long-range correlations imposed by the closure condition, these Gap are not the Kirkwood-Buff integrals. In the same sense, the relations (8.49), (8.51), and (8.53) hold true because of the closure condition with respect to the individual particles A and C. Clearly, one cannot conclude from (8.49) that the PS of W is zero. The sign of PS of W is determined by the difference GWa and Gwc, provided that GWa and GWc are evaluated in a system open with respect to the three components. 

One of the most important applications of the theory of PS is to biomolecules. There have been numerous studies on the effect of various solutes (which may be viewed as constituting a part of a solvent mixture) on the stability of proteins, conformational changes, aggregation processes, etc., (Arakawa and Timasheff 1985 Timasheff 1998 Shulgin and Ruckenstein 2005 Shimizu 2004). In all of these, the central quantity that is affected is the Gibbs energy of solvation of the biomolecule s. Formally, equation (8.26) or equivalently (8.28), applies to a biomolecule s in dilute solution in the solvent mixture A and B. However, in contrast to the case of simple, spherical solutes, the pair correlation functions gAS and gBS depend in this case on both the location and the relative orientation of the two species involved (figure 8.5). Therefore, we write equation (8.26) in an equivalent form as  

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