Polysaccharide conformation. Part IX. Monte Carlo calculation of conformational energies for disaccharides and comparison with experiment

Abstract

The treatment of conformational energies that has already been tested for monosaccharides is now applied to disaccharides and tested against available evidence for the crystalline state and solutions. van der Waals, polar, and torsional terms are included as before, with thermodynamic averaging over all possible conformations of side groups. Inter-residue hydrogen bonding is also included, in a way that allows for non-linear hydrogen bonds and makes no assumptions about the particular oxygen atoms likely to participate. For the maltose residue, better agreement is obtained with experiment than has been possible with any cruder approaches used hitherto. It is possible for the first time to account simultaneously for the seven different crystal conformations and two different solution conformations. For the cellobiose residue the agreement is at least as good as any obtained before. For both systems it is possible to define the favourable regions of conformational space more closely than by any previous approach. A major disadvantage of the method is that it involves extended computation.