Molecular level studies of hydration phenomena relevant to biological self-assembly processes.

摘要

The biological structure, stability and function of biomolecules and biomolecular assemblies in aqueous solutions are governed predominately by the unique structural and thermodynamic properties of water. This thesis focuses primarily on the theoretical and computational studies of hydration of solutes in solution. In particular, hydration thermodynamics of solutes in aqueous solutions is mapped extensively as a function of the size and charge of the solute, and different solution conditions such as temperature, pressure, and the presence of additives. This work not only builds a fundamental understanding of solvation phenomena in condensed matter, but also provides useful insights into the role of key intermolecular interactions that drive biological self-assembly.; Hydrophobic and ionic interactions together comprise the key stabilizing forces for self-assembly. Here, exhaustive studies are presented of the hydration of solutes as a function of their geometry and chemistry and in different solutions conditions. In each case, the importance of the molecular nature of water to the thermodynamics of macroscopic processes is highlighted. For example, the molecular nature of water results in disparate hydration physics for small nonpolar solutes as compared to large hydrophobic interfaces. Similarly, the asymmetry in ionic hydration with respect to the charging direction is also connected to the molecular nature of water and the inherently asymmetric charge distribution on the water molecule itself. The significance of this asymmetry is indeed shown to be related directly to the strength of association of two oppositely charged ions as well, suggesting that ionic hydration studies could be used as a sensitive tool for the parametrization of water models and ion-water interaction potentials applied in biological context.; The studies of hydration and association of simple solutes in solutions are extended to explain macroscopic phenomena relevant to biology by building a molecular volcano plot that captures the ion-ion association strength as a function of the differences in the ionic hydration free energies. Specifically, the stability of micellar structures formed by cationic surfactants as a function of the size of the counter-ions is shown to be consistent with the volcano plot interpretation.