Hi Andrew You don't say what your protein is crystallised in, or has seen during purification, but maybe S- MERCAPTOCYSTEINE might fit? (search for CSS in MSD CHEM) Do you have lower wavelength data that you might get a sulphur anomalous signal to check this?
S-methyl Cysteine might fit as well - but the difference peak and bond lengths look more S-S than S-C. Hope this helps, Dave 2008/5/22 Andrew Gulick <[EMAIL PROTECTED]>: > Greetings. > > I'm wondering if anyone has ever seen something like this. I have a 2.1 A > data set (synchrotron data) that is nearing completion. I see density that > appears to join a cysteine side chain to a lysine (30 residues away from > each other in primary sequence). There is a picture of the density here. > > http://labs.hwi.buffalo.edu/gulick/cyslys.html > > I have modeled this in as a Cysteine sulfenic acid (Side chain is Cb-Sg-OH) > and refined. There remains a bit of positive Fo-Fc density above the oxygen > and the lysine N and sulfenic acid hydroxyl are 1.8A away. > > I have some other crazy ideas but haven't been able to find any precedent in > the literature. Any thoughts on what this might be or if anyone has seen > something similar would be greatly appreciated. > Andy > > > > > > -- > Andrew M. Gulick, Ph.D. > ----------------------------------- > (716) 898-8619 > Hauptman-Woodward Institute > 700 Ellicott St > Buffalo, NY 14203 > ----------------------------------- > Senior Research Scientist > Hauptman-Woodward Institute > Dept. of Structural Biology, SUNY at Buffalo > > http://www.hwi.buffalo.edu/Faculty/Gulick/Gulick.html > http://labs.hwi.buffalo.edu/gulick > -- ============================ David C. Briggs PhD Father & Crystallographer http://www.dbriggs.talktalk.net AIM ID: dbassophile ============================
