Applications of a simple reaction force field for polarization, H-bonding, and proton transfer in peptides and water

PHYS 308

Seyit Kale, Graduate Program in Biophysics and Structural Biology, Brandeis University, Waltham, MA 02454 and Judith Herzfeld,, Department of Chemistry, Brandeis University, Waltham, MA 02454.
Interactions involving water depend on group polarizability, hydrogen bonding, and proton transfer. Recently we have shown that all of these phenomena are captured by a simple model of water inspired by the traditional Lewis construct. The model comprises explicit oxygen cores, valence electron pairs, and protons, all interacting via pair-wise pseudo-potentials that reflect Heisenberg uncertainty and Pauli exclusion. These independently mobile particles produce stable neutral, protonated and deprotonated water clusters. They also exhibit transport of protons and proton-holes through water chains. The corresponding model for ammonia also shows hydrogen bonding and the transport of protons. As a first step toward extending this approach to peptides and proteins, we have now built “Lewis” amino acids. In in vacuo simulations, zwitterionic forms of the amino acids evolve to non-ionic forms via an intramolecular proton transfer during which the proton undergoing transfer transiently interacts with both the amine nitrogen and a carboxyl oxygen.

PHYS Poster Session - Water Mediated Interactions
7:30 PM-10:00 PM, Wednesday, August 20, 2008 Pennsylvania Convention Center -- Hall C, Poster

Division of Physical Chemistry

The 236th ACS National Meeting, Philadelphia, PA, August 17-21, 2008