Improved parameters for generating partial charges: Correlation with observed dipole moments

The Universal Force Field was initially combined with the Charge Equilibriu m Scheme in the molecular mechanics program AMMP in order to generate parti al charges for protein atoms. A new parameter set with improved generation of partial charges has been derived in order to analyse a wider range of at oms and compounds. The electrostatic parameters were modified to achieve be tter correlation with experimental dipole moments for a training set of 160 compounds, which included alkali metal halogenides, saturated and unsatura ted hydrocarbons, alcohols, ethers, amines, thiols, sulphides, oxo compound s, aromatic and heteroaromatic molecules. The correlation coefficient for t he calculated and experimental dipole moments was improved from 0.57 to 0.9 8. The new parameters were tested for another 149 compounds and the correla tion coefficient increased from 0.48 to 0.85. The newly generated Modified Parameter Set for AMMP (MOPSA) improves the predictive power of the program , especially in the area of the macromolecular modelling and drug design, w here the nonbonded energies play a crucial role.