The primary objective of the SAXS program at BioCAT is to provide the biomedical community access to the small angle x-ray scattering instrument and to maintain the state-of-the-art. BioCAT has nurtured a user program with a rich history of productive collaborations that include a diverse set of biomedical interests. User support is provided 24/7 for onsite users, and BioCAT provides remote collaborations that involve a high degree of beamline personnel participation. There are two broad categories of experiments performed under the SAXS program: equilibrium and time-resolved SAXS. Liquid chromatography SAXS (LC-SAXS) constitutes > 90% of the equilibrium SAXS program. LC-SAXS in combination with a coflow sample cell, based on a design first adopted by the Australian SAXS beamline, has streamlined SAXS data acquisition at BioCAT by nullifying common concerns such as sample heterogeneity and radiation damage induced capillary fouling. Introduction of in-line multi-angle light scattering (MALS) and dynamic light scattering (DLS) detectors has further enhanced the scope and quality of data acquired using our equilibrium SAXS instrument. As part of the time-resolved SAXS program, three different options are available which cater to time regimes from ~80 microseconds to several seconds. The stopped-flow mixer or a laminar-flow mixer are recommended for accessing time regimes between a millisecond and a few seconds, depending on the amount of sample available and the system being studied. The chaotic flow mixer is used to access earlier time regimes (~ 80s to ~ 90 ms). Optimized fluid delivery systems, coordinated triggering mechanisms, and GUI based user-friendly software tools developed in house have now made the continuous flow time-resolved SAXS instrument at BioCAT one of its kind in the world and open to the general user community. BioCAT also maintains the widely used open-source data analysis program BioXTAS RAW. Maintenance and upgrade plans cover improved liquid chromatography systems, data analysis software, and microfluidic mixers, as well as upgraded computing, data storage capabilities, network infrastructure, and detectors. We will fully optimize the instrument to take advantage of the world class beam that will be provided by the APS-U project. Last but not the least we will continue to increase automation for SAXS data acquisition in order to make the user as independent as possible.
