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                SEMINAR OF THE DYNAMICAL SYSTEMS GROUP
        Institute for Computational Sciences and Informatics
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 A computational study of enzyme (RNase A) catalyzed transphosphorylation

                            Morris Krauss
             CARB/ Center for Advanced Research in Biotechnology and
                National Institute of Standards and Technology
			    Gaithersburg, MD

	The transphosphorylation step in the enzyme-catalyzed hydrolysis of
phosphate esters by Ribonuclease A (RNase A) is explored using ab initio 
quantum chemical methods. All chemically active components in the active 
site are included in the all-electron model. The remainder of the active
site, including ten residues  and six bound water molecules, is treated 
using effective fragment potentials(EFP) incorporated directly into the 
Hamiltonian of the quantum system. The EFP's are constructed to represent 
the electrostatics and polarization fields of these residues. The 
stationary points on the reaction energy surface reveal several proton 
transfer steps between the substrate and active site residues with 
activation energies consistent with experiment. The reaction energy 
surface is calculated at the Hartree-Fock level but the effect of electron 
correlation is explored with Moller-Plesset perturbation (MP2) and density 
functional methods.
		        Monday , November 20, 1995
			         5:30 pm
		         Room 206, Science & Tech. I
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