On Sat, Nov 5, 2011 at 3:02 PM, Caitlyn Claire Yeykal <cait...@uchicago.edu> 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?
Many cofactors can cause this - the ones I'm familiar with are LLP and NAD, but there are quite a few others, and they will often co-purify with the proteins that bind them. Possibly certain metals as well, but I'm less certain about that. You may be able to identify the responsible molecule from the absorbance across the visible light spectrum, although I found it difficult to track down information on peak absorbances when I last tried this several years ago. -Nat
