MOLECULAR-DYNAMICS SIMULATION OF CELLOBIOSE IN WATER

The conformational behavior of cellobiose was studied by molecular dyn amics simulation in a periodic box of waters. Several different initia l conformations were used and the results compared with equivalent vac uum simulations. The average positions and rms fluctuations within sin gle torsional conformations of cellobiose were affected only slightly by the solvent. However, water damped local torsional librations and t ransitions. The conformational energies of the solute and their fluctu ations were also sensitive to the presence of solvent. Intramolecular hydrogen bonding was weakened relative to that observed in vacuo due t o competition with solvating waters. All cellobiose hydroxyl groups pa rticipated in intermolecular hydrogen bonds with water, with approxima tely eight hydrogen bonds formed per glucose ring. The hydrogen bondin g was predominantly between water hydrogens and solute hydroxyl oxygen s. Intermolecular hydrogen bonding to ring and bridge oxygens was seld om present. The diffusion coefficients of both water and solute agree closely with experimental values. Water interchanged rapidly between t he solvating first shell and the bulk on the picosecond time scale.