Hi Mike et al. One issue that can crop up when you display CA balls + ribbon is that the CA atoms may appear to be floating away from the ribbon. This is because the default ribbon path is smoothed. You can make the ribbon go exactly through the CA atom positions by using cardinal spline instead of the default B-spline: ribspline card ... there are several command options for parameter tweaking, including smoothing just the beta-strands: ribspline card smooth strand Example image: <http://www.rbvi.ucsf.edu/chimera/features.html#ribspline> Further details: <http://www.rbvi.ucsf.edu/chimera/docs/ContributedSoftware/ribbonstyle/ribbon...> <http://www.rbvi.ucsf.edu/chimera/docs/UsersGuide/midas/ribspline.html> Best, Elaine ----- Elaine C. Meng, Ph.D. UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco