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Influence of N(1) protonation on the orientation of the N(6) substituent in hypermodified nucleic acid base N 6 ‐( N ‐glycylcarbonyl) adenine
Author(s) -
Tewari Ravindra
Publication year - 1997
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/(sici)1097-461x(1997)62:5<551::aid-qua11>3.0.co;2-8
Subject(s) - protonation , substituent , intramolecular force , chemistry , hydrogen bond , dihedral angle , stereochemistry , nucleic acid , crystallography , molecule , organic chemistry , ion , biochemistry
The influence of protonation at N(1) on the conformational preferences of the N(6) substituent in the modified nucleic acid base N 6 ‐( N ‐glycylcarbonyl) adenine, gc 6 Ade, was investigated by the quantum chemical perturbative configuration interaction using localized orbitals (PCILO) method. The preferred orientation of the glycylcarbonyl substituent changes on the protonation of N(1). In the preferred conformation, the carbonyl oxygen O(10) is placed on the same side as N(1)H and provides stabilization through intramolecular hydrogen bonding of O(10) with HN(1). The amino acid component is so oriented that the carboxyl oxygen O(13b) is aligned closely with the N(6)H direction. Thus, the preferred molecular orientation is further stabilized by intramolecular hydrogen bonding involving HN(6) with O(13b). The alternative conformation has 0.5 kcal/mol higher energy than has the preferred conformation. The preferred conformation is about 1 kcal/mol more stable than is the conformation obtained by the flipping of torsion angle β alone, from the favored orientation for the unprotonated gc 6 Ade. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 62: 551–556, 1997