It's also possible that there's oxidation in the buffer causing the yellow color. I'm not sure how common this is with HEPES. But I see it all the time with MOPS. Alternatively, does the yellow color bind the column during purification? If so, then it sounds like a co-purified flavin or protein.
Best regards, Reginald McNulty On Nov 5, 2011, at 5:57 PM, Caitlyn Claire Yeykal wrote: > Thanks for all the replies -- there are no suggestions in the literature or > in crystallized or predicted domain structures that this protein binds a > cofactor, and, although I did purify it in insect cells, PAGE gels and > activity assays support the assertion that it's not ferritin. Nobody has > seen any metal ions bound, either, but there are a few domains that haven't > been crystallized, so maybe. Again, thanks for all the possibilities; will > keep them in mind. > > Caitlyn > > On Nov 5, 2011, at 5:02 PM, Caitlyn Claire Yeykal wrote: > >> Hi -- has anyone had crystals that are colored in regular (unpolarized) >> light? Mine are yellow, and I'm not aware of anything in the buffer >> conditions that might cause this. I read online that glutaraldehyde can >> turn protein crystals a golden color, but as far as I know there isn't any >> of that in the well. Purified in HBS pH 7.2; crystallized in >> LiCl/PEG4K/Tris pH 8. Any explanations? >> >> Thanks! >> Caitlyn >> >> ____________________________________ >> Caitlyn C. Yeykal >> Mrksich Group/Adams Group >> Dept. of Biochemistry, University of Chicago >> 929 E. 57th St., Rm 547B >> Chicago, IL 60615 >> cait...@uchicago.edu >
