AMBER Archive (2004)

Subject: AMBER: RESP charges in Fe+3 heme system

From: Sebastian Fernandez Alberti (seba_at_unq.edu.ar)
Date: Thu Aug 26 2004 - 12:43:08 CDT

Dear all,
I am calculating partial charges for a heme-Fe+3 system. The Fe atom is
bounded to the 4 pirrolic N, a SH2 as ligand and the proximal histidine.
The total charge or the system is +1. Using a BLYP/6-31G* basis, I have
obtained a MK partial charge for the Fe atom= 1.36. But RESP partial
charges at the same lavel of approximation, give me a Fe partial charge=
-1.9. That is unreasonable for a Fe+3 atomic center. I am using the RED
program and a Fe atomic radius of 1.8. I would like to use RESP partial
charge in order to define atomic similarities and groups of atoms with
a net total partial charges. Can anybody suggest me what could be wrong
in the RESP calculation?
Thanks in adavance,
Sebastian Fernandez Alberti

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