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
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>
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