Published online by Cambridge University Press: 22 January 2016
Molecular replacement (MR) is a well-established computational method for phasing in macromolecular crystallography. In MR searches, spaces of motions are explored for determining the appropriate placement of rigid single-body (or articulated multi-rigid-body) models of macromolecules. By determining a priori which portions of motion space correspond to non-physical packing arrangements with symmetry mates in collision, it becomes feasible to construct more efficient MR techniques which avoid searching in these non-realizable regions of motion space. This paper investigates which portion of the motion space is physically realizable, given that packing of protein molecules in a crystal are subject to the constraint that they cannot interpenetrate, and gives explicit expressions for the volume of the non-realizable regions for crystals in two-dimensions.
(1) This paper is an expanded version of a paper delivered at the Workshop on Robotics Methods for Structural and Dynamic Modeling of Molecular Systems in July 2014 at Berkeley, CA (cs.unm.edu/amprg/rss14workshop/PAPERS/Chirikjian.pdf).