2020同步年報

112 ACTIVITY REPORT 2020 The first component of the experimental endstation is a millisecond shutter (with an opening time of 8 ms) that reg- ulates the exposure of a sample to the beam. Subsequently, an intensity attenuator, comprising 10 thin foils of various metals and thicknesses, can selectively suppress the X-ray beam in 4−23 keV, up to 8 orders of magnitude in intensity. The X-ray beam is collimated with a set of all-tungsten S3- slits at position 31.47 m and two sets of JJ-slits situated re- spectively at ~10 and ~800 mm before the sample position at 40 m. The beam position and intensity are monitored in situ with two diamond X-ray beam position monitors (XBPM) of Rigi (gap 20 µm between the quadrants) and Civi-1 (gap 3 µm) situated before and after the attenuator, with resolution 1 µm. A modified high-performance liq- uid chromatograph (HPLC) is available for on-line sample purification. The HPLC system is coupled with synchronized measurements of SAXS/WAXS, UV-vis absorption and refractive index (RI) arranged along the elution path of the HPLC ( Fig. 5(a) ). The combined measurements allow resolving solution structures and compositions of biomac- romolecules and their complexes in one sample elution. Uniquely designed is an integrated detecting system com- prising an Eiger X 9M detector (active area 233 × 245 mm 2 ) of the Dectris for SAXS and a custom-designed Eiger X 1M detector (79.9 × 77.2 mm 2 ) for WAXS. The latter has a large open slot (30 × 60 mm 2 ) by the edge of the active detector area for simultaneous SAXS-WAXS without much block- ing the view angle of the SXAS detector ( Fig. 4(c) ). These two X-ray detectors of pixel resolution 75 × 75 µm 2 move Fig. 4 : (a) CSS graphic view of experimental endstation TPS 13A components. (b) A side view of the 12-m long, 1.5 m dia. vacuum vessel for accommo- dating the (c) in-vacuum Eiger X 1M and X 9M pixel detectors that can move independently with multiple degrees of freedom in the vacuum vessel for simultaneous and coordinated SAXS and WAXS data collections. (d) Also shown is the custom-designed TPS13A Eiger X 1M, with an opening of dimensions of 30 mm by 60 mm for SAXS traversing. independently with multiple degrees of freedom inside a large vacuum vessel of length 12 m and diameter 1.5 m, providing dynamic and quick changes in the detecting con- figuration for optimized data collections ( Fig. 4(a) ). Figure 5(b) demonstrates a case of simultaneous SAXS/WAXS measurements with the on-line HPLC/UV-vis/RI system for a model protein of bull serum bovine, covering a wide q -range. The merged data can be described with the crystal structure of a protein data back (PDB id: 3B03) up to q = 1.0 Å −1 , demonstrating the success of the uniquely combined BioSAXS-WAXS measurements of TPS 13A , which would open a new standard and research trend in studying solu- tion structures of biomacromolecules. The TPS BioSAXS beamline has shown its facilities that outperform many worldwide SAXS beamlines through the unique features demonstrated. These include (1) the high-flux mode with integrated measurements of SAXS/ WAXS/UV-vis-absorption/refractive-index and an on-line HPLC system, allowing frontier studies of biomacromolec- ular solution structures and kinetics over wide length and time scales, (2) USAXS mode to resolve hierarchical struc- tures of bio-machinery assemblies up to length scale µm, and (3) microbeam SAXS/WAXS for correlated crystal and nanostructural mappings. This new dedicated TPS BioSAXS beamline aims to provide user-friendly routine measure- ments and cutting-edge research opportunities on biolog- ical structures for the domestic research community and overseas users. (Reported by U-Ser Jeng, with the inputs (c) (d) (a) (b)