mm3 Potential energy surfaces of the 2-linked glucosyl trisaccharides α-kojitriose and β-sophorotriose Original Research Article

The adiabatic potential energy surfaces (PES) of two trisaccharides with 2-linkages (α-kojitriose and β-sophorotriose) were obtained using the mm3 force field, and are represented by a single 3D contour map for which the energy is plotted against the two ψ glycosidic angles. In spite of the proximity of the positions where the two monosaccharidic units are linked to the central monosaccharide, an almost independent behavior of both linkages was found for the α-linked trisaccharide α-kojitriose, i.e., the surfaces are those expected from the maps of the disaccharide containing the same linkage. A slight shift of the position of the global minimum is found to occur, due to a hydrogen bond between the third and first monosaccharide units, which also leads to an increase in flexibility. On the other hand, for the β-linked trisaccharide β-sophorotriose, the surface is sharply different from that expected by observation of the disaccharide map. Some of the expected minima cannot appear unless a serious deformation of the φ and/or ψ angles is produced. Furthermore, the global minimum corresponds to a combination of different conformations for each of the linkages, whereas another minimum with only slightly higher energy has both glycosidic linkages in a conformation less favored for the disaccharide, though close to that predicted in crystal diffraction studies.