Molecular force field development for saccharides using the SPASIBA spectroscopic potential. Force field parameters for α- d-glucose

Abstract

Force field parameters for saccharides have been developed for the SPASIBA potential energy function. SPASIBA is derived from the amber potential energy expression to which a set of Urey-Bradley-Shimanouchi spectroscopic terms were added. Force field parameters have been refined in order to simultaneously reproduce experimental geometries from crystal structures and infrared and Raman vibrational spectra. These parameters which encompass structural and dynamical aspects can be used with confidence for further molecular mechanics and molecular dynamics studies. In the present work we concentrate on the development of parameters for α- d-glucose and water. In the first step of force field development, the monosaccharide α- d-glucose parameters were approximated based on intramolecular parameters previously established for the SPASIBA potential (alkanes, aliphatics, amino acids, alcohols and ethers). Because of the large influence of hydrogen bonds, always present in sugars, a system was studied that was composed of α- d-glucose + 6H 2O with 11 hydrogen bonds. Uncertainties with the assignments of the vibrational spectra of glucose complicate the determination of the parameters. On the other hand, the spectra of smaller molecules were correctly assigned. Hydrogen bond parameters were developed on a small system, methanol + H 2O, and then transferred to the glucose system.