Easing Exhaustive Rigid-Body And Flexible Fitting In Ucsf Chimera

Build macromolecular models from cryo-electron microscopy (EM) density maps requires fitting strategies to localize available atomic structures. To this end, we developed several approaches that are efficient enough to run as command line tools on commodity hardware. For rigid-body fitting, ADP_EM employed spherical harmonics to speed up the rotational part of the exhaustive, whereas for flexible fitting, iMODFIT exploit Normal Model Analysis to reduce the explored conformational space. Here we present the update and integration of such tools into UCSF Chimera enabling interactive macromolecular fitting into this powerful visualization tool which is the facto standard of the EM community.