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Or you could try crystallizing the protein in the presence of KI or NaI, and collect some in-house SAD data. You could also try to boost the concentration and number of ordered halide sites by quick soaking the crystals with a higher concentration of the iodide salt. In my limited experience with iodide soaks, the crystals often crack with high concentrations (close to 1.0 M) of the iodide salt, but lower concentrations (close to 0.1-0.2 M) of the salt don't result in a high enough anomalous signal to phase the structure. I've never tried it with such a small protein, so perhaps you will be successful. Diana On Sep 25, 2008, at 6:03 AM, amit sharma wrote: > > Dear CCP4bbers, > I have a protein molecule(~9.0 kDa) that crystallized in the > presence of 0.15M KBr and HEPES pH 7.0. Since there is no > homologuous structure present, I intend to perform heavy metal > derivatization. I read some literature which suggested that I could > carry out quick soak with 0.5M Sodium iodide. I was wondering if I > could soak my crystals with a similar concentration of NaBr and > collect some low resolution data at the in-house source? In addition > should I try to also introduce other heavy metals? it might be worth > mentioning that my protein carries no methionine/cys residues. > I have no prior experience in doing this. So, it would be of great > help if I could be directed towards literature/protocols pertaining > to this. Any advice/suggestions would be greatly appreciated. > > Thanks in advance > -- > Amit Sharma * * * * * * * * * * * * * * * * * * * * * * * * * * * * Diana R. Tomchick Associate Professor University of Texas Southwestern Medical Center Department of Biochemistry 5323 Harry Hines Blvd. Rm. ND10.214B Dallas, TX 75390-8816, U.S.A. Email: [log in to unmask] 214-645-6383 (phone) 214-645-6353 (fax)