Hi Warren, Changing selenomethionine residues (MSE) to methionine (MET) is one of the options in Dock Prep (under Tools... Structure Editing). <http://www.cgl.ucsf.edu/chimera/docs/ContributedSoftware/dockprep/dockprep.h...

More generally, you can change the element or other things about an atom using the Modify Atom section of the Build Structure tool (also under Tools... Structure Editing). <http://www.cgl.ucsf.edu/chimera/docs/ContributedSoftware/editing/editing.htm...

I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. meng@cgl.ucsf.edu UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco http://www.cgl.ucsf.edu/home/meng/index.html On Mar 9, 2009, at 7:55 PM, Warren Menezes wrote:

** High Priority **

Hi! I was wondering if it is possible to replace a Selenium atom in a protein with a Sulfur atom? The reason is because Sulfur has parameters. Thanks! Warren M Chicago