title: Programming new geometry restraints: parallelity of atomic groups.
abstract: Improvements in structural biology methods, in particular crystallography and cryo-electron microscopy, have created an increased demand for the refinement of atomic models against low-resolution experimental data. One way to compensate for the lack of high-resolution experimental data is to usea prioriinformation about model geometry that can be utilized in refinement in the form of stereochemical restraints or constraints. Here, the definition and calculation of the restraints that can be imposed on planar atomic groups, in particular the angle between such groups, are described. Detailed derivations of the restraint targets and their gradients are provided so that they can be readily implemented in other contexts. Practical implementations of the restraints, and of associated data structures, in theComputational Crystallography Toolbox(cctbx) are presented.
authors: Lawrence Berkeley National Laboratory, One Cyclotron Road, MS64R0121, Berkeley, CA 94720, USA.
authors: Oleg V
authors: OV
authors: Sobolev
authors: Lawrence Berkeley National Laboratory, One Cyclotron Road, MS64R0121, Berkeley, CA 94720, USA.
authors: Pavel V
authors: PV
authors: Afonine
authors: Lawrence Berkeley National Laboratory, One Cyclotron Road, MS64R0121, Berkeley, CA 94720, USA ; Department of Bioengineering, University of California Berkeley, Berkeley, CA 94720, USA.
authors: Paul D
authors: PD
authors: Adams
authors: Centre for Integrative Biology, IGBMC, CNRS-INSERM-UdS, 1 rue Laurent Fries, BP 10142, 67404 Illkirch, France ; Département de Physique, Faculté des Sciences et des Technologies, Université de Lorraine, 54506 Vandoeuvre-lès-Nancy, France.
authors: Alexandre
authors: A
authors: Urzhumtsev
keywords: PHENIX; atomic model refinement; cctbx; gradient calculation; parallel planes; restraints