Exploration of the four-dimensional-conformational potential energy hypersurface of N-acetyl-L-aspartic acid N′-methylamide with its internally hydrogen bonded side-chain orientation

Joseph C.P. Koo, Gregory A. Chass, Andras Perczel, Ödon Farkas, Ladislaus L. Torday, Andras Varro, Julius Gy Papp, Imre G. Csizmadia

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Abstract

Side-chain conformational potential energy hypersurfaces have been generated and analyzed for each of the nine possible backbone conformers of N-acetyl-L-aspartic acid-N′ methylamide. A total of 37 out of the 81 possible conformers were found and optimized at the B3LYP/6-31G(d) level of theory. The relative energies as well as the stabilization exerted by the side-chain on the backbone have been calculated, at this level of theory, for the 37 optimized conformers. Various backbone-backbone (N-H⋯O=C) and backbone-side-chain (N-H⋯O=C; N-H⋯OH) hydrogen bonds were analyzed. The appearance of the notoriously absent αL backbone conformer was attributed to such a backbone-side-chain (BB-SC) hydrogen bonds as well as a very unusual backbone-backbone (BB-BB) hydrogen bond.

Original languageEnglish
Pages (from-to)6999-7009
Number of pages11
JournalJournal of Physical Chemistry A
Volume106
Issue number30
DOIs
Publication statusPublished - Aug 1 2002

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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