PARENT SESSION
Posters P4Aa Chlorophyll and bilin based antenna systems. Abstracts (239-271)

Molecular modeling and simulation of the Photosystem II core complex in its natural lipid-water environment. Serguei Vassiliev^*,1, Doug Bruce¹, ¹ Brock University, St. Catharines, Ontario, Canada

ABSTRACT- The dynamic interaction of chromophores and electron transfer cofactors with their protein environment affects their electronic structures and is critical for efficient photosynthetic function. In this contribution we give an account of our ongoing effort to understand excited state dynamics, trapping and charge separation in photosystem II at the atomic level. We have used Density Functional Theory calculations to develop force field parameteres for all PSII electon transfer cofactors (Chla, Pheoa, beta-carotene, plastoquinone-9, bicarbonate and oxygen-evolving complex) and components of the photosynthetic membrane surrounding PSII core complex (phosphatidylglycerol, monogalactosyl diacylglycerol and digalactosyl diacylglycerol) compatible with the AMBER molecular mechanical force field. We describe the preparation and initial equilibration of the simulation system, consisting of the PSII core, lipid bilayer and water. The complete simulation system along with PSII core components contained a total of 226,000 atoms. 538 lipids, 178 sodium ions and 38425 water residues were required to prepare the simulation system. The ongoing molecular dynamics simulation will allow us to evaluate temporal fluctuations of chromophore-protein interactions, chromophore conformations, orientations and inter-chromophore distances caused by thermal motion of protein. This information will be ultimately included in the kinetic model for excited state dynamics, trapping and charge separation in photosystem II.

KEY WORDS: molecular modeling , photosystem II, excited state dynamics