Subject: questions about charges

From: [email-masked] (Charles Martin)
Date: Wed, 28 Sep 1994 09:36:53 -0600 (CDT)

Continung the discussion about charges

After reading several posts here and some of the papers suggested,
I have some questions for the experts

(1) Consider the RESP charge model.  First, is the following assement correct?
This model seems to reliably reproduce electrostatic charges of a single
nuclear configuration, however, in order to reproduce binding energetics,
model is refit over an average of nuclear configurations.
Second, if so, then how well does this (and related models) perform in MD
simulations designed to reproduce dynamical properties?

(2) How well do point charge models perfom in dynamical simulations as well?
Can this even be assesed with the current stages of technology?

(3) In molecule-protien interactions,  are there situations where the
binding molecule greatly alters the electrstatics of the protien?
For example, imagine a high polar molecule inside a protein.  Won't the
molecule polarize the surrounding medium?  Additionally, classical polarization
dies of as (1/r^3), so I would expect this effect to be fairly long ranged?
Have there been any studies which address this (e.g. large semi-empirical
calculations of a molecule inside a protein, where the protein is also polarizable?)
What kind of models are used to represent the polarizable protein?  A polarization
tensor centerd at each atom?

==================================================================
Charles H. Martin

email: [email-masked]

US Mail:
        c/o Freed Group
        The James Franck Institute and 
        The Department of Chemistry
        The University of Chicago
        5640 South Ellis Avenue
        Chicago, Illinois  60637

Work:  (312) 702-3457
Fax:   (312) 702-5863  
==================================================================