Hydration theory for molecular biophysics.

Publisher Summary Protein stabilization by the presence of water may in part be a manifestation of hydration water destabilizing the unfolded state. This chapter presents a molecular theory of hydration that highlights the role of water in protein stabilization. The focus is on potential distribution theorem whose physical basis and statistical thermodynamic framework with applications to protein solution thermodynamics and protein folding is discussed. The chapter also presents the derivation of an extension of the potential distribution theorem, the quasi-chemical theory, and proposes its implementation to the hydration of folded and unfolded proteins. The perspective and current optimism are justified by the understanding gained from successful applications of the potential distribution theorem to the hydration of simple solutes. The developments shown in the chapter illustrate a thoroughgoing reconstruction of molecular statistical thermodynamic theory of solutions. There are several motivations for this effort, but particularly, the conventional molecular theories are not compelling for biophysical applications and do not make strong connections to the molecular intuitions involved in consideration of simulation and experiment. Some of the discussion treats basic elements of statistical thermodynamics, known in specialized settings but weightier than is typical for this setting. The chapter includes examples to clarify and reinforce the basic concepts.

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