Wydział Chemii

Lum Wang

Holger Kruse

Oleg V. Sobolev

Nigel W. Moriarty

Mark P. Waller

Pavel V. Afonine

Małgorzata Biczysko

2020

Acta Crystallographica Section D: Structural Biology

76

1184-1191

10.1107/s2059798320013194

Naukowa

Angielski

Artykuł

Electron cryo-microscopy (cryo-EM) is rapidly becoming a major competitor to X-ray crystallography, especially for large structures that are difficult or impossible to crystallize. While recent spectacular technological improvements have led to significantly higher resolution three-dimensional reconstructions, the average quality of cryo-EM maps is still at the low-resolution end of the range compared with crystallography. A long-standing challenge for atomic model refinement has been the production of stereochemically meaningful models for this resolution regime. Here, it is demonstrated that including accurate model geometry restraints derived from ab initio quantum-chemical calculations (HF-D3/6-31G) can improve the refinement of an example structure (chain A of PDB entry 3j63). The robustness of the procedure is tested for additional structures with up to 7000 atoms (PDB entry 3a5x and chain C of PDB entry 5fn5) using the less expensive semi-empirical (GFN1-xTB) model. The necessary algorithms enabling real-space quantum refinement have been implemented in the latest version of qr.refine and are described here.

quantum refinement, protein, crystallography, cryo-EM, real-space refinement, phenix.comparama

http://dx.doi.org/10.1107/s2059798320013194