Parametrizing a polarizable force field from ab initio data. I. The fluctuating point charge model

We have developed a polarizable force held for peptides, using all-atom OPL S (OPLS-AA) nonelectrostatic terms and electrostatics based on a fluctuatin g charge model and fit to ab initio calculations of polarization responses. We discuss the fitting procedure, and specific techniques we have develope d that are necessary in order to obtain an accurate, stable model. Our mode l is comparable to the best existing molecular mechanics force fields in re producing quantum-chemical peptide energetics. It also accurately reproduce s many-body effects in many cases. We believe that straightforward extensio ns of our linear-response electrostatic model will significantly improve th e accuracy for those cases that the present model does not adequately addre ss. (C) 1999 American Institute of Physics. [S0021-9606(99)52402-1].