Multi-wavelength anomalous diffraction method for I and Xe atoms using ultra-high-energy X-rays from SPring-8

The first successful multi-wavelength anomalous diffraction (MAD) experiments using ultra-high-energy X-rays (∼35 keV) were performed for iodine and xenon derivatives of hen egg-white lysozyme crystals. The beamline BL41XU of SPring-8 enabled the collection of high-quality MAD data, which led to the calculation of anomalous or dispersive difference Patterson maps that determined the positions of iodine and xenon atoms. The electron density maps obtained by the density modification method for both cases proved to be of sufficient quality for building molecular models. I-MAD and Xe-MAD phasing are now available at SPring-8, and the utilization of ultra-high-energy X-rays will make a significant contribution to the solution of the phase problem in protein crystallography.