Consistent force fields for saccharides

Consistent force fields for carbohydrates were hitherto developed by extensive optimization ofpotential energy function parameters on experimental data and on ab initio results. A wide range of experimental data is used: internal structures obtained from gas phase electron diffraction and from x-ray and neutron diffraction, vibrational frequencies, dipolemoments, unit cell dimensions and lattice energies. The range of model compounds covered so far includes alkanes, ethers, alcohols, ketones and mono- and disaccharides. Electrostatic interactions are handled by fractional charges assigned to individual atoms. Charges are modeled such that Mulliken population analyses are reproduced. Morse functions are used for all bonded interactions; experimentally deriveddissociation energies are used as parameters. Van der Waals interactions are modeled with Lennard-Jones 12-6 functions.The anomeric and exo-anomeric effects are accounted for without addition of specific terms. The work is done in the framework of the Consistent Force Field which originatedin Israel and was further developed in Denmark. The actual methods and strategies employed havebeen described previously. Extensive testing of the force field is reported, and ways and means ofimprovement are indicated. Principles of mapping of conformational space are discussed, and adiscussion on which properties to preferentially reproduce in modeling is invited.