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Solving proteins at non‐atomic resolution by direct methods
Author(s) -
Burla Maria Cristina,
Carrozzini Benedetta,
Cascarano Giovanni Luca,
Giacovazzo Carmelo,
Polidori Giampiero
Publication year - 2015
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s1600576715016970
Subject(s) - phaser , ab initio , resolution (logic) , direct methods , probabilistic logic , electron density , set (abstract data type) , chemistry , atomic model , computational chemistry , molecular physics , atomic physics , algorithm , crystallography , physics , computer science , electron , quantum mechanics , optics , programming language , artificial intelligence
A new probabilistic formula estimating triplet invariants and capable of exploiting a model electron‐density map gradually created during the ab initio phasing process has been tested on a set of protein structures with data at non‐atomic resolution. All the structures contain heavy atoms larger than Ca, and show a structural complexity which may attain the level of about 8000 non‐hydrogen atoms in the asymmetric unit. It is shown that the majority of such structures may be solved by our direct methods procedure, which, in combination with a number of ancillary phasing tools, weakens the traditional expectation that atomic resolution is a necessary ingredient for the success of a direct ab initio phasing.