Open AccessLow‐resolution refinement tools in REFMAC 5
Author(s) -
Nicholls Robert A.,
Long Fei,
Murshudov Garib N.
Publication year - 2012
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s090744491105606x
Subject(s) - sharpening , deblurring , computer science , resolution (logic) , algorithm , reliability (semiconductor) , inverse , inverse problem , noise (video) , exploit , low resolution , image (mathematics) , high resolution , artificial intelligence , image processing , mathematics , physics , image restoration , mathematical analysis , power (physics) , geometry , computer security , remote sensing , quantum mechanics , geology
Two aspects of low‐resolution macromolecular crystal structure analysis are considered: (i) the use of reference structures and structural units for provision of structural prior information and (ii) map sharpening in the presence of noise and the effects of Fourier series termination. The generation of interatomic distance restraints by ProSMART and their subsequent application in REFMAC 5 is described. It is shown that the use of such external structural information can enhance the reliability of derived atomic models and stabilize refinement. The problem of map sharpening is considered as an inverse deblurring problem and is solved using Tikhonov regularizers. It is demonstrated that this type of map sharpening can automatically produce a map with more structural features whilst maintaining connectivity. Tests show that both of these directions are promising, although more work needs to be performed in order to further exploit structural information and to address the problem of reliable electron‐density calculation.