The mission of the Biophysics Collaborative Access Team (BioCAT) is to provide user access to a state-of-the- art synchrotron beamline (18ID) for diffraction and scattering of non-crystalline biological materials at the Advanced Photon Source, Argonne National Lab. Continued evolution of the beamline since first light in 1997 has resulted in a unique in the USA fiber diffraction program, and a world-class Bio-SAXS program with unique capabilities both in the equilibrium and time-resolved realms. The use of size exclusion chromatography in line with the SAXS camera has ensured unprecedentedly high data quality even with biochemically challenging samples otherwise thought to be intractable for SAXS. The recent incorporation of MALS and DLS in line with SEC allows additional biophysical characterization that can be invaluable in interpreting SAXS data from difficult systems. Our new coflow sheath flow sample cell has revolutionized SAXS data acquisition by preventing radiation damage, enhancing efficiency accompanied by significant increases in signal to noise. BioCAT maintains specialized apparatuses for combined time-resolved X-ray diffraction and physiological studies of cardiac and skeletal muscle. These studies have extended in scope from basic biophysical problems to address new disease models including cardiomyopathies. A traditional strength is fiber diffraction of general fibrous protein systems that has recently expanded into scanning diffraction imaging of fibrous protein structures in complex tissue samples. A major strength of the resource is the experienced and dedicated scientific staff who assist users seven days a week in data acquisition, processing, analysis and interpretation. BioCAT is directed by Dr. Thomas Irving, who has more than 20 years of experience overseeing synchrotron facilities for non-crystalline diffraction and scattering. Dr. Jesse Hopkins oversaw installation of the new coflow SAXS sample cell, established new user-friendly GUI based data acquisition interfaces, and provide advanced tools to interpret SEC-SAXS data. Dr. Hopkins develops and maintains the BioXTAS RAW SAXS data processing and analysis software package and will extend it to allow increased automation to optimize productivity while minimizing on-site effort for users. Dr. Srinivas Chakravarthy BioCAT?s resident biochemist coordinates the SAXS user program, assists users with conducting experiments on site, and also maintains the biochemical infrastructure. Dr. Weikang Ma is an expert in fiber diffraction of muscle and is responsible for providing comprehensive support to all our fiber diffraction users. All four of these individuals are involved in training and dissemination activities, including scientific publications, presentations at conferences, organization of BioCAT workshops and participating in community organized workshops. BioCAT has an updated website with a comprehensive set of instructions for all aspects of the resource that are sufficient for a user to plan and execute successful experiments at the beamline. Together the SAXS and Fiber Diffraction user programs host 70-90 user groups per year and consistently produce 30-40 publications per year.
The proposed resource will continue to provide state-of-the-art facilities with unique capabilities for muscle/fiber diffraction and macromolecular SAXS to the bio-medical and structural biology community. Through our fiber diffraction program, we hope to illuminate the mechanisms behind pathologies such as inherited cardiomyopathies, traumatic brain injury, and cancer metastasis. The SAXS program studies molecular complexes essential for cell function including those involved in human pathologies and can provide rational bases for drug design.