RIDL: a tool to investigate radiation-induced density loss

An automated tool, RIDL (Radiation-Induced Density Loss), has been developed that enables user-independent detection and quantification of radiation-induced site-specific changes to macromolecular structures as a function of absorbed dose. RIDL has been designed to extract suitable per-atom descriptors of radiation damage, based on changes detectable in F-obs,F- n - F-obs,F- 1 Fourier difference maps between successive dose data sets. Subjective bias, which frequently plagues the interpretation of true damage signal versus noise, is thus eliminated. Metrics derived from RIDL have already proved beneficial for damage analysis on a range of protein and nucleic acid systems in the radiation damage literature. However, the tool is also sufficiently generalized for improving the rigour with which biologically relevant enzymatic changes can be probed and tracked during time-resolved crystallographic experiments.