Mlce. Kouwijzer et al., AN EXTENSION OF THE GROMOS FORCE-FIELD FOR CARBOHYDRATES, RESULTING IN IMPROVEMENT OF THE CRYSTAL-STRUCTURE DETERMINATION OF ALPHA-D-GALACTOSE, Acta crystallographica. Section B, Structural science, 51, 1995, pp. 209-220
For carbohydrates the GROMOS force field has been extended to a more r
ealistic all-atom model, with the use of parameters from the force fie
ld proposed by Ha, Giammona, Field & Brady [Carbohydr. Res. (1988), 18
0, 207-221]. This extended and modified GROMOS force field has been us
ed to simulate the crystal structures of seven monosaccharides. The re
sults, compared with the experimental data, are satisfactory, and an o
verall improvement over those obtained with the comparable Ha force fi
eld. The experimentally determined positions of the H atoms should be
used with caution in this comparison, and the thermal parameters can o
nly be used as indicators for the preservation of the symmetry during
the simulation. The simulations gave rise to suspicion about the hydro
xyl H-atom positions in two of the sugars. These two structures were r
edetermined by X-ray diffraction at low temperature. For beta-D-glucos
e essentially the same structure was found as in the original publicat
ion. In the case of alpha-D-galactose, the new structure confirmed the
results from the simulation, in contrast to earlier experimental dete
rminations.