Hi Ed, Are there conformational changes in this process, or do chains simply move as rigid bodies? I had thought there were conformational changes within chains, but now looking at your movie again, I'm not sure. If each rigid body is a separate model, you would simply save the different configurations of the entire set as named positions with the command "savepos". Then you can reset to successive named over a specified number of frames with "reset" or smoothly interpolate over multiple saved positions with "fly". There have been recent improvements including addition of "fly" so I'd recommend a recent daily build if it sounds like this approach is doable. The process would then be scripted in a Chimera command file rather than appearing as playback in MD Movie. Once the command file generates the desired movie content, you could put a "movie record" command at the top and "movie stop" and "movie encode" commands at the bottom. example command files: http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/movies.html#examples I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. meng@cgl.ucsf.edu UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco http://www.cgl.ucsf.edu/home/meng/index.html