Subject: Heme charges

From: Emad Tajkhorshid <emad/at/ks.uiuc.edu>
Date: Tue, 5 Aug 2003 11:52:27 -0500 (CDT)

Hi,

We just optimized the geometry of a porphyrin ring using DFT and
calculated ESP charges for the molecule. The iron carries a significant
amoount of positive charge according to population analyses done on the
system (it is formally 2+), but the ESP charge for it is negative! The
iron atom is completely burried inside the molecule, and that may be one
reason of getting this strange result. Has anybody else had similar 
problems? Any comments, references, or suggestions are
appreciated.

Thanx a lot. 
Emad
------------------
Emad Tajkhorshid, Ph.D.        http://www.ks.uiuc.edu/~emad  
Assistant Director of Research
NIH Resource for Macromolecular Modeling and Bioinformatics

Theoretical and Computational Biophysics Group
Beckman Institute, 405 N. Mathews,  Urbana,  IL 61801,  USA
Tel:(217)244-4361 Fax:(217)244-6078 Email: emad/at/ks.uiuc.edu