Conformational analysis of sulfated disaccharides using the MM2 force-field

The conformational maps of six derivatives of the disaccharide alpha-D-Galp-(1 --> 3)-beta-D-Galp sulfated in different positions were obtained using variants of the MM2 force-field and compared to that of the non-sulfated disaccharide. The conformational flexibility of the glycosidic linkage is slightly affected by sulfation. While sulfation on position 4- of the beta-galactose unit shifts the global minimum to positive psi (defined by C1'-O3-C3-H3) angles, sulfation on position 2- of the same unit deepens the energy well at negative psi angles. On the other hand, sulfation on the alpha-galactose unit has little effect, if at all.