Hello, Currently there is no "force field" functionality within Chimera, and thus no minimization/dynamics. At this point you would need to use AMBER or SYBYL to perform those types of calculations. We plan to have such capability in the future, but it is a nontrivial operation. Elaine =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Elaine C. Meng, R.Ph., Ph.D. Babbitt Lab and Computer Graphics Lab meng@cgl.ucsf.edu http://www.cgl.ucsf.edu/home/meng/index.html =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=