From owner-chemistry@ccl.net Mon Oct 30 07:30:49 1995 Received: from bedrock.ccl.net for owner-chemistry@ccl.net by www.ccl.net (8.6.10/950822.1) id HAA08844; Mon, 30 Oct 1995 07:30:37 -0500 Received: from msi.com for Don_Gregory@msi.com by bedrock.ccl.net (8.6.10/950822.1) id HAA03915; Mon, 30 Oct 1995 07:30:35 -0500 Received: from qmail-gw.msi.com by msi.com (4.1/SMI-4.1) id AA17531; Mon, 30 Oct 95 07:24:35 EST Message-Id: Date: 30 Oct 1995 08:38:13 -0400 From: "Don Gregory" Subject: charges in CHARMm To: "Comp. Chem. Listserver" X-Mailer: Mail*Link SMTP-QM 3.0.2 Subject: Time:8:22 AM OFFICE MEMO charges in CHARMm Date:10/30/95 On 30 Oct., Dr. Andrey Bliznyuk wrote asking about CHARMM(m) charges. Partial atomic charges have been developed in the CHARMm force-field in a consistent way, basically involving the ESP method published in the literature, followed by scaling so as to fit the intermolecular energies (obtained from ab initio calculations) between waters placed nearby the model compound. This procedure is detailed in the beginning of the CHARMm parameter handbook. In addition, a great deal of effort has been put into a facility named the "parameter chooser" within Quanta, which uses a rule-based approach to nominate charges as a first approximation. These rules have been chosen to match, as closely as possible, those charges that have been developed in the above method, and allows then the user to extend to novel systems, by first deciding on atom-types in the local environment, then using the rules to suggest charges that the user can then change if so desired. Don Gregory Quanta/Protein Product Manager Biosym/Molecular Simulations