Molecular dynamics study on the conformational stability of laminaran oligomers in various solvents

Solution conformations of the (1-->3)-beta -D-glucan laminaran have been in vestigated by means of molecular mechanics and molecular dynamics simulatio ns in three solvents: water, dimethylformamide, and dimethyl sulfoxide. Con formational analysis of solvated laminarabiose was carried out to study the effect of specific solute-solvent interactions upon reactive hydroxyl grou ps. Dynamic trajectories of solvated laminarabiose have been interpreted in terms of average glycosidic-linkage conformation, hydrogen-bonding pattern , and coordination by solvent molecules. The analysis of radial distributio n functions, coordination functions, mean residency times, and time correla tion functions derived from the simulation trajectories furnished the neces sary insight. The results have been used to assess the steric accessibility of laminaran-C4-OH and -C6-OH hydroxyl groups in the considered solvents a nd to rationalize corresponding earlier experimental observations. The expe riments demonstrated that reaction equilibrium during chemical modification of laminaran oligomers with 2,2-dimethoxypropane involving the laminaran-C 4-OH and -C6-OH hydroxyl groups significantly depended on the solvent used.