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Home | Seminars and Symposia | Past seminars/symposia: Thursday, February 28, 2002

DTC Seminar Series

Computer Simulations of Biological Systems: From Opsin Shifts to Enzymatic Reaction


Jiali Gao
Department of Chemistry

Thursday, February 28, 2002
1:00 pm

402 Walter Library

Professor Gao has employed a combined quantum mechanical and molecular mechanical (QM/MM) simulation method to investigate the origin of the opsin shift in bacteriorhodops in (bR) in the membrane matrix. Professor Gao found that both solvation and interactions with the protein significantly shifts the absorption maximum of the retinal protonated Schiff base, but the effects are much more pronounced in polar solvents than in the protein environment. Structural analysis of the PSB binding site in the lipid membrane revealed the specific interactions that make contributions to the observed opsin shift. In addition, the effects of amino acid mutations on the absorption energy in the visual pigment rhodopsin have been analyzed. Present studies of enzymatic reactions, including the reaction mechanism of orotidine 5'-monophosphate (OMP) decarboxylase will also be discussed. OMP decarboxylase is the most proficient enzyme known today, which catalyzes the last decarboxylation step in pyrimidine nucleotide biosynthesis. This computational study reveals that ground state destabilization effects provide the dominant contribution to the enzymatic rate acceleration, whereas, transition state stabilization only plays a minor role.


Professor Gao received a B.S. from Beijing University in 1982, and his Ph.D. from Purdue University in 1987 under the direction of William L. Jorgensen. After post-doctoral research at Harvard University with Professor Martin Karplus, he joined the faculty in the Department of Chemistry at the State University of New York at Buffalo in 1990, where he remained as Professor of Chemistry until 1999. He moved to the University of Minnesota in 2000. His research interests include development and applications of computational methods for studies of chemical reactions in solution and enzymes.