Hi Shu-hao Liou, You could manually build the spin label onto the cysteine atom by atom, or if you had a separate spin label structure already, you could open it as a separate model and then attach it to the cysteine of your protein. Probably the latter would be easier, if you already have such a structure. If you have a structure with the spin label on some other protein, you could just delete the other protein first. Manually building atom by atom would be with Build Structure (in menu under Tools… Structure Editing), the Modify Structure section. Joining the separate parts would be with Build Structure, the Join Models section. See the Build Structure docs for details: <http://www.rbvi.ucsf.edu/chimera/docs/ContributedSoftware/editing/editing.ht...> I hope this helps, Elaine ---------- Elaine C. Meng, Ph.D. UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco

On Aug 10, 2015, at 2:53 PM, Shu-Hao Liou <sliou@ucdavis.edu> wrote:

Hi, Thank you for reading this email. I'd like to have a rough protein structure with certain spin label on one of the cysteine. Is chimera be able to provide the reasonable structure for that? Sincerely, Shu-hao Liou UC Davis