DEVELOPMENT OF MICRO-WAXS AND MICRO-SAXS SET-UP

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Aim2 of Core Project 2 for the BiOCAT project is Time Resolution Small-Angle X-ray Scattering. The combined use of microfluidics technique with Small-Angle X-ray Scattering allows probing microsecond timescales. For these techniques to work, the X-ray beam size has to be smaller than the fluid path to reduce the background and collect good data quality. Here we evaluated the use of the microprobe optics for micro-WAXS experiments. A diode was installed on a 2.8mm diameter beam stop to record transmission. The sample detector distance was 280mm. The beam was focused on the detector. 8mg/ml folded cytochrome C solution was loaded on the flow cell. Good quality scattering data were obtained with Rg values in agreement with the literature. Planned improvements to the setup include moving the KB mirrors upstream to increase the sample to detector distance to access smaller Q values. We will also focus the X-ray beam to a spot between the detector and the sample to decrease the beam size at the sample and achieve a better spatial resolution along the capillary as well as better temporal resolution of the reaction. We will also \test a new microfluidic mixer. Commisioning tests are planned for late Novemerb with data collection for time resolved studies of folding of cytochrome C are planned for December.