Hi William,

The way I go about the sigma level contouring in Chimera, though it's somewhat ham-fisted but perhaps less complicated than Tom's suggestion, is to contour the region of interest at the desired sigma level in Coot or O and then play with the contouring in Chimera until both maps look as similar as possible (the maps rarely look identical for technical differences in the contouring techniques, I think). It works.

   Cheers,

               Boaz



Boaz Shaanan, Ph.D.
Dept. of Life Sciences
Ben-Gurion University of the Negev
Beer-Sheva 84105
Israel
Phone: 972-8-647-2220 ; Fax: 646-1710
Skype: boaz.shaanan