Radiation Damage in macromolecular Crystallography: why do we care?

Structural biology relies on X-ray crystallography to provide much of the three dimensional information on macromolecules that informs biological function [1]. We develop improved methods for macromolecular crystallography (MX) to enable problems not previously accessible to structure solution to be tackled. A notable example of this has been the progress in finding protocols to cryocool protein crystals prior to data 100K collection to reduce the rate of radiation damage by around a factor of 70 compared to that at room temperature [2]. However, the damage, even at 100 K, is still a limiting problem as it can prevent structure determination. It not only causes `global’ changes resulting in the fading of the diffraction pattern with increasing dose, but also induces `specific’ structural changes in the protein structures obtained. These changes can mislead the experimenter when interpreting the biology of the structure.
Current ongoing investigations include studies of 100K and RT radiation damage in macromolecular crystals in order to inform both our understanding and mitigation strategies, and full dose modelling of the diffraction experiment (RADDOSE-3D (www.raddo.se)) to allow data collection optimisation strategies [3,4].

References:

[1] EF Garman (2014).Developments in X-ray Crystallographic Structure Determination of Biological Macromolecules.
Science 343, 1102-1108
[2] EF Garman. (1999) Cool Data: Quantity and Quality. Acta Cryst D. D55, 1641-1653.
[3] OB Zeldin, M Gerstel & EF Garman (2013) RADDOSE-3D: time- and space-resolved modeling of dose in macromolecular crystallography Journal of Applied Crystallography 46, 1225-1230.
[4] OB Zeldin, S Brockhauser, J Bremridge, J Holton & EF Garman. (2013) Predicting the X-ray lifetime of protein crystals PNAS 110, 20551-20556