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Acta Crystallogr D Biol Crystallogr. 2015 Mar;71(Pt 3):646-66. doi: 10.1107/S1399004714028132. Epub 2015 Feb 26.

FEM: feature-enhanced map.

Author information

1
Physical Biosciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, MS64R0121, Berkeley, CA 94720, USA.
2
Biology and Soft Matter Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831, USA.
3
Los Alamos National Laboratory, Mail Stop M888, Los Alamos, NM 87545, USA.
4
Biochemistry and Molecular and Structural Biology, Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
5
Centre for Integrative Biology, IGBMC, CNRS-INSERM-UdS, 1 Rue Laurent Fries, BP 10142, 67404 Illkirch, France.

Abstract

A method is presented that modifies a 2mFobs - DFmodel σA-weighted map such that the resulting map can strengthen a weak signal, if present, and can reduce model bias and noise. The method consists of first randomizing the starting map and filling in missing reflections using multiple methods. This is followed by restricting the map to regions with convincing density and the application of sharpening. The final map is then created by combining a series of histogram-equalized intermediate maps. In the test cases shown, the maps produced in this way are found to have increased interpretability and decreased model bias compared with the starting 2mFobs - DFmodel σA-weighted map.

KEYWORDS:

FEM; Fourier map; OMIT; PHENIX; cctbx; density modification; feature-enhanced map; map improvement; map kurtosis; map sharpening; model bias

PMID:
25760612
PMCID:
PMC4356370
DOI:
10.1107/S1399004714028132
[Indexed for MEDLINE]
Free PMC Article

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