MOLECULAR-FORCE FIELD DEVELOPMENT FOR SACCHARIDES USING THE SPASIBA SPECTROSCOPIC POTENTIAL - FORCE-FIELD PARAMETERS FOR ALPHA-D-GLUCOSE

Force field parameters for saccharides have been developed for the SPA SIBA potential energy function. SPASIBA is derived from the AMBER pote ntial energy expression to which a set of Urey-Bradley-Shimanouchi spe ctroscopic terms were added. Force field parameters have been refined in order to simultaneously reproduce experimental geometries from crys tal structures and infrared and Raman vibrational spectra. These param eters which encompass structural and dynamical aspects can be used wit h confidence for further molecular mechanics and molecular dynamics st udies. In the present work we concentrate on the development of parame ters for alpha-D-glucose and water. In the first step of force held de velopment, the monosaccharide alpha-D-glucose parameters were approxim ated based on intramolecular parameters previously established for the SPASIBA potential (alkanes, aliphatics, amino acids, alcohols and eth ers). Because of the large influence of hydrogen bonds, always present in sugars, a system was studied that was composed of alpha-D-glucose + 6H(2)O with 11 hydrogen bonds. Uncertainties with the assignments of the vibrational spectra of glucose complicate the determination of th e parameters. On the other hand, the spectra of smaller molecules were correctly assigned. Hydrogen bond parameters were developed on a smal l system, methanol + H2O, and then transferred to the glucose system. (C) 1997 Elsevier Science B.V.