Zero‐dose extrapolation as part of macromolecular synchrotron data reduction

Radiation damage to macromolecular crystals at third‐generation synchrotron sites constitutes a major source of systematic error in X‐ray data collection. Here, a computational method to partially correct the observed intensities during data reduction is described and investigated. The method consists of a redundancy‐based zero‐dose extrapolation of a decay function that is fitted to the intensities of all observations of a unique reflection as a function of dose. It is shown in a test case with weak anomalous signal that this conceptually simple correction, when applied to each unique reflection, can significantly improve the accuracy of averaged intensities and single‐wavelength anomalous dispersion phases and leads to enhanced experimental electron‐density maps. Limitations of and possible improvements to the method are discussed.