Hi everybody, I am working on a mutant protein structure which is 56 aminoacids long and solved the structure using SAD( Single wavelength anomalous dispersion) with zinc ions. We used SHELX software to locate the Zinc atoms and solved phases. We got the structure as a monomer. The resolution of the structure is 1.4 A0 .
The problem with the structure is, when i calculate the structure factors in COOT it always shows negative electron density around ZINC atoms which have been located by SHELX. I initially thought it was because my COOT software was very old and it doesn't recognize the Zinc atoms( I am new to crystallography) . I calculated the structure factors using FFT from CCP4 and it shows the same. I don't understand the problem. It refines well in Refmac and B-factors also look very good. Anyone know what the problem is? Thank You in advance Deepthi -- Deepthi
