Acta Crystallographica Section D

Biological Crystallography

Volume 61, Part 12 (December 2005)

research papers

Acta Cryst. (2005). D61, 1643-1648 [ doi:10.1107/S0907444905033494 ]

Three-dimensional model-free experimental error correction of protein crystal diffraction data with free-R test

Z.-Q. Fu

Abstract: Experimental error correction and scaling is the last step in X-ray diffraction data processing. It is also critical in obtaining good-quality data. In this study, an algorithm is proposed to more generally and efficiently correct experimental error in X-ray crystal diffraction data. With this algorithm, the experimental error is represented by a symbolic three-dimensional function C( [xi] , [eta] , t) in the detecting space. Here, ( [xi] , [eta] ) are the coordinates of the diffraction spots on the image and t represents the data-collection time. While the theoretical form of C( [xi] , [eta] , t) is not known, it will be determined from the data through computer-aided analysis. The free R_merge is introduced to check the validity of the solution. The three-dimensional symbolic function does not carry any assumptions and thus can generally account for experimental errors in various X-ray crystal diffraction experiments that are normally too complicated to be described by any fixed formula. Tests will be given to compare the results from different algorithms.

Keywords: experimental error correction; data processing.