Subject: Charges

From: "Andrey Bliznyuk" <[email-masked]>
Date: Sat, 1 Oct 1994 18:10:43

Dear Netters,

With great interest I have read the material about determination
of charges for MM calculations. It seems, that people forgot to
mention one more approach to the problem: fitting charges to
reproduce ab-initio energy of intermolecular interactions.
This method has been used in groups of Clementi and Jorgensen.
The last references I have on my table are:

M. Aida, G. Corongiu, E. Clementi "Ab initio force field for
simulations of proteins and nucleic acids"
Int. J. Quant. Chem. 1992, v.42, p.1353-1381

J. Pranata, S.G. Wierschke, W.L. Jorgensen "OPLS potential
functions for nuclear bases. Relative association constants
of hydrogen-bonded base pairs in chloroform"
J. Am. Chem. Soc., 1991, v.113, p.2810-2819.

From general point of view, this method seems more accurate than
obtaining charges from EP, because it includes polarization.
Unfortunately, it is computationaly more expensive and it is
not clear, that it gives better results. (Once again a problem
with comparing results from different force fields).

Dr. Andrey Bliznyuk
Department of Biochemistry
University of Sydney,
NSW 2006, Australia