Improving the accuracy of macromolecular structure refinement at 7 Å resolution

Axel T. Brunger, Paul D. Adams, Petra Fromme, Raimund Fromme, Michael Levitt, Gunnar F. Schröder

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


In X-ray crystallography, molecular replacement and subsequent refinement is challenging at low resolution. We compared refinement methods using synchrotron diffraction data of photosystem I at 7.4 Å resolution, starting from different initial models with increasing deviations from the known high-resolution structure. Standard refinement spoiled the initial models, moving them further away from the true structure and leading to high R free-values. In contrast, DEN refinement improved even the most distant starting model as judged by Rfree, atomic root-mean-square differences to the true structure, significance of features not included in the initial model, and connectivity of electron density. The best protocol was DEN refinement with initial segmented rigid-body refinement. For the most distant initial model, the fraction of atoms within 2 Å of the true structure improved from 24% to 60%. We also found a significant correlation between R free values and the accuracy of the model, suggesting that R free is useful even at low resolution.

Original languageEnglish (US)
Pages (from-to)957-966
Number of pages10
Issue number6
StatePublished - Jun 6 2012

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


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