Here is a link to a picture of some mystery difference density that I find in a low resolution (2.8 but high overall B and high avg. ADPs) nestled in an area where a beta strand buckles out.
I have circled three N-H groups that seem to be pointing at it. Two are backbone amides and one is a histidine. The crystallization medium is 6 M ammonium nitrate, Tris buffer, and glycerol for cryoprotection. It looks too elongated to be a metal it almost looks as if the histidine has an adduct. The top side of the pocket is hydrophobic (pro and Leu). Can anyone give a possibility other than evil sausage density? Laurie Betts https://docs.google.com/file/d/0Bx8-qQA_HKegekZKSng1ZEV2MHM/edit
