It seems odd from energetic considerations that there would be a free-form amino acid when it "has a choice" to be involved in energetically favorable interaction. It sounds doubly odd in the case of a cystein involved in a disulfide bond. Could it be that you are observing the effects of radiation decay? If so, recollecting data with this in mind could help with refinement and with avoiding artifacts in interpretation. Sorry for not answering your question directly. Cheers, N.
Ruslan Sanishvili (Nukri), Ph.D. GM/CA-CAT, Bld. 436, D007 Biosciences Division, ANL 9700 S. Cass Ave. Argonne, IL 60439 Tel: (630)252-0665 Fax: (630)252-0667 [EMAIL PROTECTED] -----Original Message----- From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of Prasenjit Bhaumik Sent: Friday, July 06, 2007 12:46 PM To: [email protected] Subject: [ccp4bb] Double conformations of cysteine ! Hello, We are trying to refine a structure using REFMAC and we are facing problem in refining the double conformations of a cysteine residue. One conformation is involved in formation of a disulfide linkage and other conformation is free. Is there any way to define the restraints so that both the conformations can be refined. With kind regards, Prasenjit -- Prasenjit Bhaumik, Ph.D. Protein Structure Section Macromolecular Crystallography Laboratory National Cancer Institute at Frederick 1050 Boyles Street, Building-539, Room-145 P.O. Box B, Frederick, MD-21702, USA Phone: 301-846-1974, Fax: 301-846-7101 E-mail: [EMAIL PROTECTED] -------------------------------------------------
