An introduction to stereochemical restraints

Conformation-dependent restraints for polynucleotides: I. Clustering of the geometry of the phosphodiester group

The refinement of macromolecular structures is usually aided by prior stereochemical knowledge in the form of geometrical restraints. Such restraints are also used for the flexible sugar-phosphate backbones of nucleic acids. However, recent highly accurate structural studies of DNA suggest that the phosphate bond angles may have inadequate description in the existing stereochemical dictionaries...

Stereochemical restraints revisited: how accurate are refinement targets and how much should protein structures be allowed to deviate from them?

The Protein Data Bank and Cambridge Structural Database were analyzed with the aim of verifying whether the restraints that are most commonly used for protein structure refinement are still appropriate 15 years after their introduction. From an analysis of selected main-chain parameters in well ordered fragments of ten highest resolution protein structures, it was concluded that some of the cur...

Accurate macromolecular crystallographic refinement: incorporation of the linear scaling, semiempirical quantum-mechanics program DivCon into the PHENIX refinement package.

Macromolecular crystallographic refinement relies on sometimes dubious stereochemical restraints and rudimentary energy functionals to ensure the correct geometry of the model of the macromolecule and any covalently bound ligand(s). The ligand stereochemical restraint file (CIF) requires a priori understanding of the ligand geometry within the active site, and creation of the CIF is often an er...

Comment on Stereochemical restraints revisited: how accurate are refinement targets and how much should protein structures be allowed to deviate from them? by Jaskolski, Gilski, Dauter & Wlodawer (2007).

Effect of anisotropy and anharmonicity on protein crystallographic refinement. An evaluation by molecular dynamics.

Molecular dynamics simulations are employed to determine the errors introduced by anharmonicity and anisotropy in the structure and temperature factors obtained for proteins by refinement of X-ray diffraction data. Simulations (25 ps and 300 ps) of metmyoglobin are used to generate time-averaged diffraction data at 1.5 A resolution. The crystallographic restrained-parameter least-squares refine...