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Quantum chemical studies of a model for peptide bond formation. 3. Role of magnesium cation in formation of amide and water from ammonia and glycineThe SN2 reaction between glycine and ammonia molecules with magnesium cation Mg2+ as a catalyst has been studied as a model reaction for Mg(2+)-catalyzed peptide bond formation using the ab initio Hartree-Fock molecular orbital method. As in previous studies of the uncatalyzed and amine-catalyzed reactions between glycine and ammonia, two reaction mechanisms have been examined, i.e., a two-step and a concerted reaction. The stationary points of each reaction including intermediate and transition states have been identified and free energies calculated for all geometry-optimized reaction species to determine the thermodynamics and kinetics of each reaction. Substantial decreases in free energies of activation were found for both reaction mechanisms in the Mg(2+)-catalyzed amide bond formation compared with those in the uncatalyzed and amine-catalyzed amide bond formation. The catalytic effect of the Mg2+ cation is to stabilize both the transition states and intermediate, and it is attributed to the neutralization of the developing negative charge on the electrophile and formation of a conformationally flexible nonplanar five-membered chelate ring structure.
Document ID
20040120355
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Oie, T.
(The Rockefeller University, Molecular Theory Laboratory Palo Alto, California 94304, United States)
Loew, G. H.
Burt, S. K.
MacElroy, R. D.
Date Acquired
August 22, 2013
Publication Date
January 1, 1984
Publication Information
Publication: Journal of the American Chemical Society
Volume: 106
Issue: 26
ISSN: 0002-7863
Subject Category
Exobiology
Funding Number(s)
CONTRACT_GRANT: NCC2-196
Distribution Limits
Public
Copyright
Other

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