CHARACTERIZATION OF FORCE-FIELDS FOR LIPID MOLECULES - APPLICATIONS TO CRYSTAL-STRUCTURES

The nonbonded portion of a force field for lecithins was characterized by application to the study of the crystal packing geometry and energ etics of eight different molecules. The molecules were either lecithin fragments or chosen to isolate particular intermolecular features to test the accuracy of the force field specifically for those interactio ns. In particular, the hydrocarbon interactions, hydrogen bonding, ele ctrostatics, and phosphate interactions were critiqued. The results su pport previous findings that indicated that this force field is reason ably accurate for lecithins. For all molecules, a minimum was found ne ar the experimentally determined crystal structure. Using D-glucitol a s an example, it is shown that the structural effect of hydrogen bondi ng is better represented by a nonelectrostatic force-field model than by a purely electrostatic model. Results obtained with glycerylphospho choline and four smaller organic phosphate molecules suggest that furt her study of nonbonded interactions of phosphate groups is needed. (C) 1993 by John Wiley & Sons, Inc.