Conceptual design of SPring-8 contract beamline for structural biology

At SPring-8, a contract beamline has been designed and developed for structural biology by the Institute of Physical and Chemical Research (RIKEN). In structural biology, three-dimensional knowledge of biological macromolecules is indispensable for understanding biological functions: x-ray crystallography, small-angle x-ray scattering (SAXS), and x-ray-absorption fine-structure are the typical techniques. The beamline contains two experimental stations, protein crystallography and SAXS. Both experiments can be carried out simultaneously, with dichromatic synchrotron radiation emitted from two undulators in serial arrangement. The branched beams are generated by a transparent diamond crystal. The beam for the protein crystallography station is provided by the ''trichromator'' to optimize for MAD (multiwavelength anomalous diffraction) experiments. The main feature of this concept is to minimize systematic errors in anomalous dispersion measurements for MAD experiments.