Hi Anbang Li,
If you want to show the spheres in a relative size, you can use
set sphere_scale, 0.5
to scale down the size by half for example. To do this for a specific object, use
set sphere_scale, 0.5, object
Otherwise, if you want to change the actual radius, you can use
alter selection, vdw=newradius
Possibly you have to use rebuild to update the scene afterwards.
Tsjerk A. Wassenaar, M.Sc.
Groningen Biomolecular Sciences and Biotechnology Institute (GBB)
Dept. of Biophysical Chemistry
University of Groningen
9747AG Groningen, The Netherlands
+31 50 363 4336