[Chimera-users] Is it possible to change the protonation state of only one residue (histidine) of a protein ....

Hi all I'd like to know if it is possible to change the protonatation state of only one particular residue (histidine) in my protein.. I've been trying to do it using addh tool but with no success, I think it can only work with the protein as a whole, isn' it ? Please, any suggestion is welcomed Sergio -- Sergio Garay Dr. en Ciencias Biológicas Facultad de Bioquimica y Cs. Biológicas Universidad Nacional del Litoral Santa Fe - Argentina C.C. 242 - Ciudad Universitaria - C.P. S3000ZAA Argentina Ph. +54 (342) 4575-213 Fax. +54 (342) 4575-221