Professor Celeste Sagui
Department of Physics
North Carolina State University
Raleigh, NC

Monday, February 7, 2005
3:00 pm (CT)
3269 Beckman Institute

Abstract

An accurate and numerically efficient treatment of electrostatics is essential for biomolecular simulations, in particular, when a smooth interface to quantum chemical descriptions is needed. Force field used in biomolecular simulations such as AMBER and CHARMM assign ``partial charges" to every atom in a simulation in order to model the interatomic electrostatic forces. The respectiive charge values are obtained via least- squares fitting to the Coulombic potential produced by quantum chemical procedures Unfortunately, the fitting procedure for large, conformationally flexible molecules is under-determined, which is a major source of errors. There are two main problems associated with the treatment of classical electrostatics: (i) how does one eliminate artifacts associated with the point charges as used in force fields, and thereby improve the electrostatic potentials in a physically meaninful way?; (ii) how does one efficiently simulate the very costly long-range electrostatic interactions? Here, we present results on a recently developed distributed multipole method. This formalism which is based either on the Particle-Mesh Ewald summation method or on a multigrid method can treat interactions between electrostatic multipoles up to hexadecapoles without prohibitive additional computational costs. The required multipoles may be effectively computed via a new formalism based on maximally localized Wannier functions. The importance of these methods for large scale biomolecular simulations will be discussed.

Tea and coffee will be served in R3151 Beckman Institute at 2:15pm.