COMPARISON OF 2 FORCE-FIELDS BY MOLECULAR-DYNAMICS SIMULATIONS OF GLUCOSE CRYSTALS - EFFECT OF USING EWALD SUMS

To compare the GROMOS force field with one designed by Ha et al., mole cular dynamics simulations of alpha-D-glucose anhydrate and monohydrat e crystals were performed. Also, the long-range interactions were calc ulated both with a cutoff approximation and with Ewald summations. The results are compared with results obtained experimentally by neutron and X-ray diffraction. The force-field parameters had been optimized w ith the cutoff approximation; this apparently led to worse results whe n the Ewald summations were used. However, in all simulations the symm etry was roughly preserved and the mean atomic coordinates and thermal parameters, bond angles, and dihedrals without hydrogen atoms were ra ther well reproduced. The dihedrals with hydrogen atoms exhibited conf ormational transitions, which resulted in a disordered hydrogen bondin g scheme. In general, the GROMOS force field performed better than the Ha force field. (C) 1993 by John Wiley & Sons, Inc.