Hello, In principle if you have access to a tuneable X-ray beam and that you go to higher wavelengths (towards 2.5 and higher) then you'd get significant anomalous signal for Calcium and no such significant anomalous signal for Mg. Not many of these beam lines (with high flux) around though. At lower wavelengths there is less signal and therefore it becomes more and more problematic (care must be taken to collect the data). Still ca. 1.3 electrons anomalous signal at 1.54 A wavelength for Ca. HTH, Fred. On 02/03/13 18:43, Daniel Slade wrote:
I have several structures that has multiple known calcium binding sites, and I found a new site that seems to accept calcium or magnesium. I say this because if a magnesium is put in the structure, the bond lengths are ~ 2.1. But if you put a calcium in it, they go to ~2.6. All of these refinements were done without ReadySet, which I recently used with metal restraints and it seemed to change the bond length of calcium to ~2.4. I'm a bit confused as to what to do here as either metal seems to be right. Worth noting, this is a very strong metal binding site that can't be removed with 10 mM EDTA.
Any help here on how to figure this out which ion this is would be great.
Thanks in advance
Dan
_______________________________________________ phenixbb mailing list [email protected] http://phenix-online.org/mailman/listinfo/phenixbb
-- Fred. Vellieux (B.Sc., Ph.D., hdr) IBS / ELMA 41 rue Jules Horowitz F-38027 Grenoble Cedex 01 Tel: +33 438789605 Fax: +33 438785494