Title: "How Do Long-ranged Interactions Affect Hydrophobic Hydration and Association: An LMF Study"
Abstract:
Hydrophobic interactions play a key role in phenomena raging from oil-water demixing to biological processes like protein folding and membrane formation. The hydrophobicity of solutes originates from the distortion and disruption of local hydrogen bonds and the unbalanced long ranged forces acting on the interfacing waters. The slowly varying nature of long ranged Coulomb and van der Waals forces makes it possible to use local molecular field (LMF) theory, a mean-field- like approach, to theoretically account for their contribution to the hydrophobicity. In this talk, I will show how the application of a new symmetric version of LMF theory helps clarify the roles VdW attractions and long-ranged electrostatic interactions play in the solvation and association of apolar solutes in water. In the LMF approach, a minimal model of the aqueous solution with "short" water is used as a reference and LMF equations are used to show that modified solute-water and solute-solute interactions can be chosen to make the solutes have the "correct" hydrophobicity. In addition to computational advantages, LMF theory provides a simple physical picture and a conceptual framework for understanding the basic phenomena of solvent-induced effective interactions between solutes. The theory is tested for both small solutes around which the local hydrogen bonds are mainly intact and large solutes around which the local hydrogen bonds are completely broken.