13June 2023 ESRFnews

Lights, camera, action SYNCHROTRON SERIAL CRYSTALLOGRAPHY

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S beam to assemble a complete dataset, piece by piece. The technique avoids the risk of radiation damage to a single prized molecule, and, operating at room temperature, is able to expose functional conformations that might otherwise be obscured at unphysiological, cryogenic temperatures. More importantly, though, it opens up the possibility of time-resolving those conformations, by taking snapshots of the passing crystals at increasing time increments after a reaction within them is activated, for example by light, a change in pH or an interaction with a separate compound.

XFELs will always provide the highest time resolution for serial MX, as their X-ray pulses have a duration on the order of femtoseconds. However, dynamics on micro to millisecond timescales, as probed by synchrotron X-ray pulses, are relevant to the majority of molecular- biological systems, says Ivo Tews, a structural biologist at the University of Southampton. He is submitting a grant application on computing analysis to better handle serial data. Synchrotrons have the advantage of superior data quality, because of their optimised set-up geometries and detection, he says. They make it easier for the normal structural biologist.

And the EBS, the world s brightest synchrotron source, is pushing the possibilities of synchrotron serial MX to the limit. The step change is coming in now with the EBS, says Tews. We have more flux, more photons.

More photons means better time resolution. Currently, ID29 is able to fire pulses 90 µs long, but there are plans to reduce them to 10 µs or shorter, while maintaining a focal point around a micron wide. The bandwidth of the beam is unusually broad for MX experiments, too, mean- ing complete datasets can be obtained faster and with fewer diffraction images, as collected on a cutting-edge JUNGFRAU 4M detector. Other beamline projects are being inspired by our design, says Daniele de Sanctis, the scientist in charge of ID29.

ID29 is trialling at least three different sample delivery methods: fixed target, extrusion and tape-drive (see

The step change is coming in now with the

EBS. We have more flux, more photons