X-ray crystallography is the most prolific method to determine the structure of biological macromolecules – i.e. proteins, DNA, RNA and complexes thereof. It is limited by the strong damage inflicted to biological molecules by exposure to X-rays. To mitigate damage progression, crystallographic data collection has for the past decades been carried out mostly at cryogenic temperatures, yet at the risk of blocking conformational heterogeneity that can be central to biological function. The advent of serial crystallography – whereby each crystal is only exposed once, enabling distribution of the dose over a myriad of crystals – has yet allowed crystallographic experiments at room temperature to become more and more frequent, with the long-term promise of permitting time-resolved experiments on virtually all crystalline systems. The pre-requisite is, however, to have determined the maximal X-ray dose that can be safely deposited onto a crystal at room-temperature without fear of compromising the biological information. Using a new approach to raster-scanning serial crystallography, and taking advantage of the availability at ESRF-ID13 of both a highly-brilliant micro-focused X-ray beam and a latest generation detector, researchers at the IBS, the ESRF and the ILL, in collaboration with colleagues from the Universities of Oxford, San Francisco and Notre Dame, have been able to determine this dose limit and to visualize specific damage caused by X irradiation to biological molecules at room-temperature. This dose limit will serve as a yardstick for future room-temperature serial crystallography experiments to be performed at 4th generation synchrotrons. ESRF-EBS is the first of these.
Radiation damage and dose limits in serial synchrotron crystallography at cryo- and room temperatures. Eugenio de la Mora, Nicolas Coquelle, Charles S. Bury, Martin Rosenthal, James M. Holton, Ian Carmichael, Elspeth F. Garman, Manfred Burghammer, Jacques-Philippe Colletier, and Martin Weik . PNAS; doi.org/10.1073/pnas.1821522117