The Long-wavelength Macromolecular Crystallography I23 at Diamond Light Source

Abstract

Long-wavelength macromolecular crystallography（MX）has been proposed for a long time as a tool for phasing novel macromolecular crystal structures without additional heavy atom labelling. Making use of anomalous diffraction from atoms natively present in the crystal, such as sulphur and phosphorus, has become increasingly popular over the past years. Nevertheless, the full potential of this technique, has not been fully exploited due to lack of dedicated experimental setups able to easily access wavelengths longer than 2 Å. Since the wavelengths for the absorption edges of sulphur and phosphorus are significantly longer, standard beamline setups are not suitable to provide high-quality, high-resolution data, as the experiments are limited by the increasing absorption effects and the diffraction angles for longer wavelengths. Currently only two synchrotron beamlines offer access to optimised sample environments using wavelengths longer than 2.7 Å：BL1A at Photon Factory, Japan and I23 at Diamond Light Source, UK. Here, we describe the challenges and solutions implemented at the in-vacuum long-wavelength MX beamline I23 and present first results.