title: Oligosaccharide trans-glycoside 3JCOCC Karplus curves are not equivalent: effect of internal electronegative substituents.
abstract: Density functional theory (DFT) calculations show that internal electronegative substituents perturb 3JCOCC Karplus curves by phase shifting them with respect to analogous pathways devoid of this substitution. Thus, the J-coupling maximum, which normally is observed near 180 degrees , is shifted by approximately 15 degrees . These findings suggest that the two types of inter-residue C-O-C-C coupling pathways observed in many oligosaccharides cannot be treated using a generalized 3JCOCC Karplus equation. Quantitative interpretations of trans-glycoside J-couplings to evaluate linkage conformations will need to take this effect into account.
authors: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556-5670, USA.
authors: Hongqiu
authors: H
authors: Zhao
authors: Ian
authors: I
authors: Carmichael
authors: Anthony S
authors: AS
authors: Serianni
mesh_terms: D004583:Electrons; D006027:Glycosides / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009844:Oligosaccharides / Q000737:chemistry*; D044367:Phase Transition
chemical_list: D006027:Glycosides; D009844:Oligosaccharides