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Using the conformation-dependent geometry paradigm improves atomic resolution refinements

Acta Cryst. (2011). D67, 699–706 (

[Improved refinement] Improved refinement behavior using the CDL. For a test case at each resolution, the bars show the decrease in r.m.s.d. for the main-chain bond angles resulting from the refinement against the CDL as opposed to the single-value Engh & Huber restraint library. Blue bars show the improvement in assessed quality. Red bars show the real improvement.

A script has been created to allow protein refinements with SHELXL to use a conformation (φ/ψ) dependent library (CDL) of restraints. Tests at resolutions between 1.4 and 0.8 Å showed that models created using the CDL restraints had much improved geometry. For resolutions better than 0.8 Å, use of the CDL made little difference to the models, but their assessed quality was much improved. Results indicate the CDL improves refinement behavior at all resolutions. The script can be accessed at

D. E. Tronrud and P. A. Karplus