The lack of intramolecular hydrogen bonding and the side chain effect in alanine conformers

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• 作者：Rodrigo A. Cormanich ; Lucas C. Ducati ; Roberto Rittner ; ^{rittner@iqm.unicamp.br}
• 关键词：Conformational analysis ; Amino acids ; Alanine ; Hydrogen bonding ; Intramolecular interactions
• 刊名：Journal of Molecular Structure
• 出版年：2012
• 期刊代码：62_00222860
• 类别：ch
• 出版时间：25 April, 2012
• 卷：1014
• 期：Complete
• 页码：12-16
• 文件大小：660 K

摘要

Although amino acids are considered one of the most important classes of compounds found in Nature, the literature has few reports that have been made to understand the intramolecular interactions that govern their conformational energies and geometries. Actually, it has been arbitrarily assigned that possible intramolecular hydrogen bonding is the responsible force that dictates amino acid conformational preferences. In this paper, calculations at B3LYP/aug-cc-pVDZ level of theory within the NBO and QTAIM frameworks have shown that hyperconjugation and steric effects interplay, not H-bonding, are the intramolecular interactions that govern alanine conformational preferences. It is also shown that the steric interactions between the alanine methyl group side chain and its main chain influences its energies and geometries.