Identifying radiation damage and avoiding it in the first place - Elspeth Garman

Описание: Structural biology relies on X-ray crystallography to provide much of the three-dimensional information on proteins and other macromolecules that informs biological function, but radiation damage to the samples remains one of the major bottlenecks to accurate structure determined. The
radiation damage can manifest as `global’ changes resulting in the fading of the diffraction pattern with increasing dose, or as `specific’ structural and chemical changes in the protein structures obtained. It occurs during both room temperature (RT) and cryo-cooled X-ray crystallographic diffraction experiments, and is a main-stream concern [1,2]. Our understanding of its characteristics and its effects have significantly increased over the last 60 years since the first study of the phenomenon at
RT by Blake and Phillips in 1962 [3]. It has become clear that it is vital for crystallographers to be aware of the artefacts that can result from overexposing crystals, and also important that they have some knowledge of how to minimise/avoid the deleterious effects of the unavoidable absorption of the incident X-rays by the sample.
This contribution will present examples of the main symptoms of radiation damage and pointers on what can be inspected in the output from both diffraction analysis software and the modelling/refinement stages of the experiment to monitor possible radiation damage pathologies.
However, it is always better in the first place to try to reduce the rate of radiation damage to a minimum, if this is possible within the requirements of the particular experiment. Some practical suggestions on ways to achieve this will be covered, including the use of the RADDOSE-3D code [4]
(www.raddo.se) to estimate the absorbed dose and which is now implemented on a number of synchrotron beamlines round the world. A new RADDOSE-3D GUI is also available [5].

References
[1] EF Garman. (1999) Cool Data: Quantity and Quality. Acta Cryst. D55: 1641-1653.
[2] EF Garman & M Weik (2023) Radiation damage to biological macromolecules. Current Opinion Struct. Biol. 82: 102662
[3] CCF Blake & DC Phillips (1962) Effects of X-irradiation on single crystals of myoglobin. In ‘Biological Effects of Ionising Radiation at the Molecular Level’. IAEA Symposium, Vienna, P183.
[4] CS Bury, JC Brooks-Bartlett, SP Walsh & EF Garman (2018) Estimate your dose: RADDOSE-3D. Protein Science 27, 217–228
[5] https://github.com/jdickerson95/qt_RA... and paper in preparation.