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: [EMAIL PROTECTED]
214-645-6383 (phone)
214-645-6353 (fax)
