Charges on the protein?

 Dear CCLers,
 It is well known that the electrostatic interactions is one of the most
 important features in ligand-receptor binding. To calculate it, partial
 charges of both the ligand and the receptor (usually a protein molecule)
 are needed to be integrated into the Coulomb formula. If the ligand is a
 small, common organic molecule, relatively reliable values could be
 obtained by using semi-empirical algorithm. But the charges on the protein
 remain as a stumbling block. At present, many people use residue charge
 templates, which are derived from the quantum mechanical results of three
 peptides.  The drawback of doing so is obvious.
 So my question is, is there any better way to get the partial charges on
 the protein? Any experience? Any ideas? Pointers to any literature are
 also appreciated.
 Best Wishes,
 Arthur
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 _/   Arthur Wang                     Doctoral Candidate   _/
 _/   Molecular Design Lab                                 _/
 _/   Institute of Physical Chemistry, Peking University   _/
 _/   Beijing 100871, P.R.China                            _/
 _/                                                        _/
 _/   E-mail: arthur;at;ipc.pku.edu.cn                        _/
 _/   Tel: 86-10-2501490    Fax: 86-10-2501725             _/
 _/   WWW: http://www.ipc.pku.edu.cn/arthur/home.htm       _/
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