Just in the continuation of my previous mail i again want to ask few question on the metalloprotiens..Apart from factors like occupancy, B factor, coordination sphere and metal ion-ligand distances to distinguish Mg or calcium, can anomalous signal  tell the identity and the type of metal ion bound to the protein,  specifically in the case of Mg and Calcium..An anomalous data analyzed through Xtriage (phenix) gives a signal of 0.097 with Magnesium while the same gives a signal of 0.1062 with Caclium ( both data sets showing Anomalous flag as true )..can anybody shed some light on which is more true ?? the data has maximum resolution of 2.6A and i had kept Mg atom at the active site (  protein was incubated with 5mM MgCl2)..just because it is not matching a typical octahedral geometry and exact metal ion-oxygen distance as represented by Cambridge structural database (CSD) my reviewer has asked me to check anomalous signal for both Mg and Ca and ( he is expecting that scattering metal ion it to be Ca ) give appropriate reason for putting Mg there..please give suggestions..

your help would be greatly appreciated
--
Regards

Faisal
School of Life Sciences
JNU