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Do you have N-formyl methionine? In bacteria, the initiator Met is formylated on its nitrogen. The formyl is typically removed by peptide deformylase, but there are exceptions to this rule. Cheers, Artem -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dominique Monferrer Ventura Sent: Tuesday, September 26, 2006 12:21 PM To: ccp4 Subject: [ccp4bb]: methionines of the N-terminus *** For details on how to be removed from this list visit the *** *** CCP4 home page http://www.ccp4.ac.uk *** Dear all, I am at the stage of refinement of a structure and there is extra positive electron density at the N-terminii of both chains which I don't know how to explain. I have 1M mercaptoethanol in the buffer, and 2M sodium formate in the crystallization condition. The unexplained blob fits quite well with mercaptoethanol, but I wonder if this compound could have reacted with the methionines of the N-terminus? What about the formate? Thankyou for any suggestions, Dominique -- Dominique Monferrer Departament de Biologia Estructural Institut de Biologia Molecular (CSIC) c/Jordi Girona 18 Barcelona 08034 ESPANYA Tel. +34 93 400 61 00 [EMAIL PROTECTED]
