MOLECULAR-DYNAMICS SIMULATION OF SUCROSE IN AQUEOUS AND DIMETHYL-SULFOXIDE SOLUTION

Molecular dynamics simulations have been carried out to study the moti on of a single sucrose molecule in two solvents, water and dimethyl su lfoxide at 300 K. Starting from a crystal structure of sucrose, no maj or conformational transitions are observed for the dihedral angles of the glycosidic linkage, nor are they observed for any of the hydroxyme thyl groups in either of the solutions during 200 ps, the duration of the production part in both simulations. Hydroxyl groups usually show frequent transitions, except for those involved in hydrogen bonding be tween the two sugar residues in sucrose. Inter-residue hydrogen bondin g is observed between O5g and H'6f for more than half of the simulatio n time and between Olf and H'2g for about half of the simulation time both in water and in dimethyl sulfoxide. Radial distribution functions were calculated between oxygens or hydroxyl protons of the solute and solvent oxygen atoms. Radial distribution functions typical of hydrog en bonding to solvent are observed for the hydroxyl groups of sucrose except for those involved in inter-residue hydrogen bonding, where coo rdination numbers are reduced. Translational diffusion constants were calculated from the simulations and were far sucrose 1.2 x 10(-5) cm(2 ) s(-1) in water and 0.13 x 10(-5) cm(2) s(-1) in dimethyl sulfoxide.