STRUCTURAL MOLECULAR BIOLOGY SMALL ANGLE X-RAY SCATTERING STATION BEAM LINE 4-2

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The SSRL SMB small-angle x-ray scattering station BL4-2 is dedicated to structural biology studies, providing state-of-the-art experimental facilities for non-crystalline diffraction and scattering studies on proteins, protein assemblies, virus particles, biological fibers and lipid membranes. The year 2009 was the first full year of experimental run at BL4-2 since the extensive upgrades of the station and its relocation to Sector 16. A mirror pitch feedback system to mitigate beam instability issues was implemented, and resulted in a significant improvement in data quality. The fully upgraded in-hutch instrumentation features a variable-distance pin-hole geometry x-ray scattering camera system, which can be configured to accommodate several data collection modes, including solution scattering, single crystal diffraction, lipid/fiber diffraction and gracing-incidence scattering. This system covers the characteristic length scale in the range of 2 A to 2000 A with seven discrete sample-to-detector distances. A Bonse-Hart geometry ultra-small angle scattering setup is being redeveloped to extend the range up to a few microns. Recently acquired advanced x-ray detectors, Rayonix MX225HE CCD and Dectris Pilatus 300K silicon pixel array detectors, were fully characterized and put in routine operation. The former is used all x-ray scattering/diffraction experiments on BL4-2 with the exception of fast time-resolved studies, which are covered by the latter. Both detectors have demonstrated exceptional performance and high reliability. We have developed several new sample handling devices to improve data throughtput or to facilitate new types of experiments, including for high thoughput solution x-ray scattering studies. We have also developed a temperature controlled sample holder for the lipid sandwich plate (96 well micro-plate format) as well as a prototype capillary holder for flash photolysis experiments. A new interlocked personnel protection system has been developed to protect experimenters and detectors from pote