[phenixbb] Additional residue info in coot

[Brown, Breann]

Hello, 
  I am currently refining a model of a zinc-binding protein and after refinement there is additional positive Fo-Fc density at the zinc site. This is the fourth independent structure of this particular protein solved in my lab so we are confident the metal is in fact zinc. I noticed that after refinement the "residue info" in Coot has two lines for the zinc atom. The first line reads "G/121 ZN/ZN 1.00 44.30" while the second line reads G/121 ZN/ 0.00 0.00. The occupancy for the second line cannot be changed and it only appears after refinement. I carried out the same refinement using a previously solved structure of the same protein and the extra residue info line was not present. My question is where does this extra line in the residue info come from and could the zero occupancy be causing additional Fo-Fc density at the metal site?
 
Thanks, 
 Breann

Breann L. Brown
Page Laboratory
Department of Molecular Pharmacology, Physiology and Biotechnology
Brown University
Providence, RI  02912