Hi, Yes -- the spheres show atomic VDW radii, and there are several ways to change VDW radii. One way is the command vdwdefine, for example: vdwdef +0.5 C (add 0.5 angstroms to VDW radii of carbons) ~vdwdef (go back to default VDW radii) Information on VDW radii in Chimera and several ways to change them: <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/vdwrad.html> Note that changing the VDW radii will affect other calculations such as "findclash" and molecular surface generation. It may be better to use the default radii for those purposes. 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 Jan 7, 2010, at 7:10 AM, Yasser Almeida Hernández wrote:

Hi... Can i change the radius of the sphere atoms representation ...?

Thanks