Preferred conformation of the glycosidic linkage of methyl-beta-mannose.

The conformational preference of the glycosidic linkage of methyl-beta-mannose was studied in the gas phase and in aqueous solution by ab initio calculations, and by molecular dynamics (MD) and Car-Parrinello molecular dynamics (CPMD) simulations. MD simulations were performed with various water potential functions to study the impact of the chosen water potential on the predicted conformational preference of the glycosidic linkage of the carbohydrate in solution. This study shows that the trans (t) orientation of the glycosidic linkage of methyl-beta-mannose is preferred over its gauche clockwise (g+) orientation in solution. CPMD simulations clearly indicate that this preference is due to intermolecular hydrogen bonding with surrounding water molecules, whereas no such information could be demonstrated by MD simulations. This study demonstrates the importance of ab initio molecular dynamics simulations in studying the structural properties of carbohydrate-water interactions.