If you have a access to a synchrotron you can try double difference anomalous DDANO maps see Than et al. Acta Cryst. (2005). D61, 505–512 for an example
Best Roberto On 1 Jul 2014, at 16:10, Dhanasekaran Varudharasu <[email protected]<mailto:[email protected]>> wrote: Dear all, I have solved a structure (using molecular replacement) of metallo-enzyme which may have Zn or Ni at its active site. I collected data at in-house CuKa radiation. Now, I am able to locate the active site metal ion preciously but I am not able to differentiate whether it is Zn or Ni. I computed anomalous difference map and I got good anomalous map also. But still there is ambiguity, since Zn and Ni have closest F" values at CuKa radiation ( For Zn = 0.68 and For Ni = 0.51). But both, Zn and Ni have different F' values at CuKa radiation ( For Zn = -1.61 and For Ni = -3.07). My question is that, Can we used F' value information to differentiate metal ions?. Is it possible to find whether I have Zn or Ni at active site of my enzyme using crystallographic technique?. Thanks in advance -- Dhanasekaran Varudharasu Post-Doctoral Fellow Department of Oral Biology Rutgers school of Dental Medicine Rutgers Biomedical and Health Sciences Newark, NJ 07103 USA Roberto A. Steiner Group Leader Randall Division of Cell and Molecular Biophysics King's College London [email protected]<mailto:[email protected]> Room 3.10A New Hunt's House Guy's Campus SE1 1UL London Phone 0044 20 78488216 Fax 0044 20 78486435
