Protein Hydration Dynamics and Hydrophobic Force Law

by Prof. Biman Bagchi (Indian Institute of Science, Bangalore, India)

Monday 29 May 2017, 15:00 → 16:00 Europe/Rome

Aula 5 (Dip. di Fisica - Edificio E. Fermi)

Dynamics of the hydration layer surrounding a protein has drawn intense attention in the last few years, even giving rise to considerable controversies and debates. The central issue seems to be the time scale of relaxation. The estimates vary from system to system and are found to depend on the technique used. For example, dielectric relaxation provides a time scale of the order of 50-100 ps while polar solvation energy relaxation gives 1-10 ps. NMR gives yet another estimate. In addition, uncertainties exist about the width of hydration layer. We shall first provide an overview of the area and subsequently combine simulations performed on different proteins to interrogate these issues. Particular attention shall be paid to the role of amino acid side chains in hydration layer dynamics. We shall discuss the nature of hydrophobic force experienced by two parallel plates immersed inside water. We find a sharp cross-over in the distance dependence of the hydrophobic force law.