Hi Dan, As far as I know there isn't a command or script to do this. The center can can be calculated with "define centroid" (works on atoms, can be mass-weighted or not) or "measure center" (works on density maps or atoms, mass-weighted only), but to my surprise I couldn't find a way to do the rest of the calculation, other than to write your own python script. <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/define.html#centroid> <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/measure.html#center> Maybe someone with python skills can suggest a complete route. Sorry about that, 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 Feb 14, 2012, at 12:06 PM, Daniel Gurnon wrote:

Hi all, Can Chimera determine (or has a script been written to determine) the radius of gyration for a pdb structure? Dan