SOLUTION CONFORMATION OF MONOSYLLACTOSES AND DIFUCOSYLLACTOSES AS REVEALED BY ROTATING-FRAME NOE-BASED DISTANCE MAPPING AND MOLECULAR MECHANICS AND MOLECULAR-DYNAMICS CALCULATIONS

The solution conformation of two fucosyllactoses, Fucalpha(1 --> 2)Galbeta(1 --> 4)Glcalpha,beta and Galbeta(1 --> 4) [Fucalpha(1 --> 3)] Glcalpha,beta, and a difucosyllactose, Fucalpha(1 --> 2)Galbeta(1 --> 4) [Fucalpha(1 --> 3)] Glcalpha,beta, were investigated in Me2SO-d6 with the use of distance mapping, molecular mechanics (MM) energy minimization and molecular dynamics (MD) simulations. The distance mapping procedure, which was based on rotating-frame NOE constraints involving C- and O-linked protons, and hydrogen bonding constraints, suggested the occurrence of two conformations for each of the fucose residues. The MM calculations resulted in two minima that were located reasonably near to the regions demarcated in the PHI, PSI conformational space by distance mapping; 500 ps MD trajectories showed transitions between two conformations characterized by glycosidic angles PHI and PSI that only deviated insignificantly from those found by the first two methods. No similar transitions were observed for the Galbeta1 --> 4Glc linkage.