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Relaxed potential energy surfaces of N ‐linked oligosaccharides: The mannose‐α(1 → 3)‐mannose case
Author(s) -
Imberty Anne,
Tran Vinh,
Pérez Serge
Publication year - 1990
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.540110206
Subject(s) - glycosidic bond , disaccharide , conformational isomerism , chemistry , potential energy surface , potential energy , maxima and minima , computational chemistry , mannose , work (physics) , molecular dynamics , chemical physics , stereochemistry , thermodynamics , molecule , classical mechanics , physics , organic chemistry , mathematics , mathematical analysis , enzyme
We report calculations of potential energy surfaces where all the internal coordinates of the disaccharide Man‐α(1 → 3)‐Man‐α‐O‐Me were relaxed and minimized through an extensive molecular mechanics scheme. Flexibility within the mannopyranose rings plays a crucial role. Introduction of the relaxed principle into the conformational description of the disaccharide does not greatly alter the overall shape of the low‐energy domains but it reveals new local minima. However, its principle effect is the lowering of energy barriers in the potential energy surface. New conformational transitions about the glycosidic bonds appear, permiting pathways among the low energy sections. This occurs with only little variation of the classical 4 C 1 conformation of the mannopyranose residues. All the conformations observed in the solid state, along with those already predicted through the joint use of NMR and modeling techniques, fall into the populations of stable conformers calculated in the present work. Moreover, a satisfactory agreement is reached between previously observed NOE values, and the theoretical one, calculated from the averaging of more than 500 microstates. The present results reconciliate most of the apparently conflicting data previously reported; they provide strong support for the application of the concept of conformational averaging to solution behavior. Some limitations of the proposed methodology are also discussed.