CC* - Linking crystallographic model and data quality

Kay Diederichs

University of Konstanz, Protein Crystallography and Molecular Bioinformatics, 78457 Konstanz, Germany
Kay.Diederichs@uni-konstanz.de

 

Historically, Rmerge (also called Rsym) has been considered as an indicator of X-ray data quality, and e.g. decisions about exposure time, total rotation range, and suitability of datasets for refinement were based on it. Recently it has been pointed out [1] that the high-resolution value of Rmerge is not related to Rwork/Rfree of a crystallographic model, and is therefore unsuitable to define a resolution cutoff. Å more meaningful indicator (CC1/2) has been suggested and a derived quantity (CC*) was shown to be limiting for CCwork/CCfree of a crystallographic model. As a consequence, crystallographers are now in a position to better understand the properties of their data, which may be used to obtain more accurate crystallographic models.

 

1.       Karplus P. A. and Diederichs K., Science, 2012, 336, 1030-1033