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Modeling of methyl transfer reactions in S-Adenosyl-L-Methionine dependent enzymesVelichkova, Polina January 2006 (has links)
<p>A very important trend for studying biomolecules is computational chemistry. In particular, nowadays it is possible to use theoretical methods to figure out the catalytic mechanism of enzyme reactions. Quantum chemistry has become a powerful tool to achieve a description of biological processes in enzymes active sites and to model reaction mechanisms.</p><p>The present thesis uses Density Functional Theory (DFT) to investigate catalytic mechanism of methyltransferase enzymes. Two enzymes were studied – Glycine N-MethylTransferase (GNMT) and Guanidinoacetate Methyltransferase (GAMT). Different models of the enzyme active sites, consisting of 20 to 100 atoms, are employed. The computed energetics are compared and are used to judge the feasibility of the reaction mechanisms under investigation.</p><p>For the GNMT enzyme, the methyl transfer reaction was found to follow an SN2 reaction mechanism. The calculations demonstrate that the mechanism is thermodynamically reasonable. Based on the calculations it was concluded that hydrogen bonds to the amino group of the glycine substrate lower the reaction barrier, while hydrogen bonds to carboxylate group raise the barrier.</p><p>In the GAMT enzyme the methyl transfer reaction was found to follow a concerted asynchronous mechanism which includes transfer of a methyl group accompanied by a proton transfer taking place simultaneously in the same kinetic step. The calculated barrier agrees well with the experimental rate constant. i</p>
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The generalized valence bond description of the PI electron states of conjugated moleculesLevin, George B. January 1900 (has links)
Thesis (Ph. D.)--California Institute of Technology, 1974. UM #74-21,599. / Title from home page. Viewed 01/15/2010. Includes bibliographical references.
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A generalized valence bond description of vacancy and impurity states in diamond and siliconSurratt, Grover Timothy. Goddard, William A., January 1976 (has links)
Thesis (Ph. D.)--California Institute of Technology, 1976. UM #76-13,137. / Advisor names found in the Acknowledgements pages of the thesis. Title from home page. Viewed 01/15/2010. Includes bibliographical references.
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I. The generalized valence bond theory of electronic structure. II. An orbital interpretation of superexchange in antiferromagnetic insulatorsHay, Philip Jeffrey. Goddard, William A., January 1972 (has links)
Thesis (Ph. D.)--California Institute of Technology, 1972. UM #72-22,603. / Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 01/20/2010. Includes bibliographical references.
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New concepts of metallic bondingMcAdon, Mark Herbert. Goddard, William A., January 1988 (has links)
Thesis (Ph. D.)--California Institute of Technology, 1988. UM #88-03,406. / Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 01/20/2010. Includes bibliographical references.
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I. Projected G1 wavefunctions for He₂. II. Localized wavefunctions for H₂O, OH, and OGuberman, S. Goddard, William A., January 1900 (has links)
Thesis (Ph. D.)--California Institute of Technology, 1973. UM #73-14,307. / Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 01/21/2010. Includes bibliographical references.
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I. Theoretical studies of photoionization II. The electronic structure of linear polyenes /Nascimento, Marco Antonio Chaer. Goddard, William A., January 1978 (has links)
Thesis (Ph. D.)--California Institute of Technology, 1978. UM #78-15,981. / Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 01/21/2010. Includes bibliographical references.
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I. Orbital interpretation and properties of the X¹Sigma⁺, a³Pi, A ³Pi and ³Sigma⁺ states of BH. II. Gas phase reactions of fluoromethyl cations with ethylene and benzeneBlint, Richard Joseph. Goddard, William A., Beauchamp, Jesse L. January 1900 (has links)
Thesis (Ph. D.)--California Institute of Technology, 1972. UM #73-01,525. / Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 02/01/2010. Includes bibliographical references.
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Theoretical and experimental assessment of the viability of 1,4,6,9-spiro[4.4]nonatetrayl as a reactive intermediateMcElwee-White, Lisa. Goddard, William A., Dougherty, Dennis A., January 1984 (has links)
Thesis (Ph. D.)--California Institute of Technology, 1984. UM #84-04,516. / Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 02/01/2010. Includes bibliographical references.
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I. The electron structure of the Criegee intermediates. II. The electronic structure of pyrazine. III. Approximate integral methods and correlated wavefunctionsWadt, Willard Rogers. Goddard, William A., January 1975 (has links)
Thesis (Ph. D.)--California Institute of Technology, 1975. UM #75-09,542. / Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 02/08/10. Includes bibliographical references.
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