Recent developments in the instrumentation and data analysis of synchrotron small-angle X-ray scattering (SAXS) on biomolecules in solution have made biological SAXS (BioSAXS) a mature and popular tool in structural biology. This article reports on an advanced endstation developed at beamline 13A of the 3.0 GeV Taiwan Photon Source for biological small- and wide-angle X-ray scattering (SAXS-WAXS or SWAXS). The endstation features an in-vacuum SWAXS detection system comprising two mobile area detectors (Eiger X 9M/1M) and an online size-exclusion chromatography system incorporating several optical probes including a UV-Vis absorption spectrometer and refractometer. The instrumentation and automation allow simultaneous SAXS-WAXS data collection and data reduction for high-throughput biomolecular conformation and composition determinations. The performance of the endstation is illustrated with the SWAXS data collected for several model proteins in solution, covering a scattering vector magnitude q across three orders of magnitude. The crystal-model fittings to the data in the q range ∼0.005-2.0 Å-1 indicate high similarity of the solution structures of the proteins to their crystalline forms, except for some subtle hydration-dependent local details. These results open up new horizons of SWAXS in studying correlated local and global structures of biomolecules in solution. 

Performance of the new biological small- and wide-angle X-ray scattering beamline 13A at the Taiwan Photon Source

Cancer-targeted fucoidan‑iron oxide nanoparticles for synergistic chemotherapy/chemodynamic theranostics through amplification of P-selectin and oxidative stress.

This study aims to quantitatively investigate the effect of water content on the self-assembly behavior of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) in tetrahydrofuran/water cosolvents by small-angle X-ray scattering. PS-b-PEO chains preferentially form fractal aggregates at a dilute concentration in neat tetrahydrofuran (THF). By adding a small amount of water into THF, PS-b-PEO forms gelled networks. The gelled networks have correlated inhomogeneities, which were generated through mesophase separation. These gelled networks are not present when PS-b-PEO is dissolved in THF/methanol and THF/ethanol cosolvents. The substitution of water with 12 M HCl reduces the viscosity of the gelled networks. Those results indicate that the gelled networks of PS-b-PEO need hydrogen bonds formed from surrounding water molecules to be bridging agents, which connect different PEO block chains together. Upon increasing the water content in THF/water cosolvents, dispersed micelles with a core-shell conformation or aggregated micelles preferentially coexist with fractal aggregates.

Structural Evolution of a Polystyrene-Block-Poly(Ethylene Oxide) Block Copolymer in Tetrahydrofuran/Water Cosolvents.

The synthesis of the cell-wall peptidoglycan during bacterial cell division is mediated by a multiprotein machine, called the divisome. The essential membrane protein complex of FtsB, FtsL and FtsQ (FtsBLQ) is at the heart of the divisome assembly cascade in Escherichia coli. This complex regulates the transglycosylation and transpeptidation activities of the FtsW-FtsI complex and PBP1b via coordination with FtsN, the trigger for the onset of constriction. Yet the underlying mechanism of FtsBLQ-mediated regulation is largely unknown. Here, we report the full-length structure of the heterotrimeric FtsBLQ complex, which reveals a V-shaped architecture in a tilted orientation. Such a conformation could be strengthened by the transmembrane and the coiled-coil domains of the FtsBL heterodimer, as well as an extended β-sheet of the C-terminal interaction site involving all three proteins. This trimeric structure may also facilitate interactions with other divisome proteins in an allosteric manner. These results lead us to propose a structure-based model that delineates the mechanism of the regulation of peptidoglycan synthases by the FtsBLQ complex. 

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Structure of the heterotrimeric membrane protein complex FtsB-FtsL-FtsQ of the bacterial divisome

Introduction In 2019, the Cornell High Energy Synchrotron Source (CHESS) completed its most significant upgrade in nearly 40 years of operation. This upgrade included removal of the three-story-tall particle physics detector, replacement of one-sixth of the Cornell Electron Storage Ring (CESR), and a complete remodel of the experimental floor, including installation of six new undulator-fed beamlines. These modifications enabled a transition from CESR’s historical running mode with counter-circulating positrons and electrons to single-beam operation, resulting in significant improvements to CESR’s properties and performance as an X-ray source. Completion of the upgrade coincided with adoption of a new model for CHESS funding, by which partner institutions sponsor one or more beamlines in addition to a portion of the operational funding of CHESS and CESR. Though beamlines remain owned and operated by Cornell, the mission, core capabilities, and beamtime allocation model of each beamline are determined by the partner. The Materials Solutions Network at CHESS (MSN-C) is one of several new sub-facilities emerging from this change. MSN-C is a sponsored program of the Air Force Research Laboratory based on two end stations with complementary capabilities: the Structural Materials Beamline (SMB/ID1A3) operates from 40 to 200 keV and is optimized for the study of metals and other high-density materials [1, 2], while the Functional Materials Beamline (FMB/ID3B) operates at a series of discrete energies from 10 to 30 keV and is optimized for soft materials such as polymer composites and thin films. Together, the resources and access model of MSN-C represent an unprecedented effort to develop and apply state-of-the-art synchrotronbased techniques to real-world manufacturing challenges faced by industry, such as determination of residual stress in as-manufactured parts [2]. This includes new challenges associated with emerging materials and processing, such as 3D printing of polymer composites, additive manufacturing of metals, and autonomous approaches to materials synthesis. This article describes the layout and capabilities of FMB, along with several examples showcasing its use. The design of FMB was driven by two primary goals. The first was to enable both real-space and reciprocal-space interrogation of heterogeneous components such as those based on polymer-matrix composites. This goal is addressed by implementation of two complementary modes of operation: scanning X-ray microdiffraction (XMD) [3] based on simultaneous smalland wide-angle X-ray scattering (SAXS and WAXS), and full-field imaging. XMD enables determination of variation in crystalline and molecular ordering, defects, and heterogeneities at the micron scale, but with data acquisition times limited by the need to raster a sample through the beam. Full-field imaging, referring here to imaging without the use of an imaging optic downstream of the sample, permits 2D images exhibiting radiographic and/or phase contrast to be collected in parallel at approximately 1 μm resolution and at frame rates limited only by detector frame rate and incident intensity. The second goal was to enable in-situ studies of highly non-equilibrium phenomena related to materials fabrication and processing, such as the evolution of microstructures, strain, and heterogeneities. This goal is addressed in several ways, especially the ability to accommodate large environments around the sample, custom detector configurations, python-based experimental control, synchronization of data acquisition with user-supplied equipment, and robust, flexible support for fly-scan operation, in which data acquisition occurs during continuous motor motion. A third FMB design priority was minimizing the time and labor required to accommodate different experimental systems and modalities. This priority is manifest in a highly automated, modular setup in the hutch in which the upstream flightpath and detector tables can easily switch among different configurations. Similarly, the sample table may be completely exchanged in about an hour, permitting complicated setups to be partially or wholly configured outside the hutch before the beamtime for which it is needed begins, then quickly transferred into place. Since first light at FMB in October 2019, this rare combination of capabilities has demonstrated unique utility for the study of soft materials.

https://www.tandfonline.com/doi/pdf/10.1080/08940886.2023.2202578?needAccess=true&role=button

The Functional Materials Beamline at CHESS

The optical design and performance of the recently opened 13A biological small-angle X-ray scattering (SAXS) beamline at the 3.0 GeV Taiwan Photon Source of the National Synchrotron Radiation Research Center are reported. The beamline is designed for studies of biological structures and kinetics in a wide range of length and time scales, from angstrom to micrometre and from microsecond to minutes. A 4 m IU24 undulator of the beamline provides high-flux X-rays in the energy range 4.0–23.0 keV. MoB4C double-multilayer and Si(111) double-crystal monochromators (DMM/DCM) are combined on the same rotating platform for a smooth rotation transition from a high-flux beam of ∼4 × 1014 photons s−1 to a high-energy-resolution beam of ΔE/E ≃ 1.5 × 10−4; both modes share a constant beam exit. With a set of Kirkpatrick–Baez (KB) mirrors, the X-ray beam is focused to the farthest SAXS detector position, 52 m from the source. A downstream four-bounce crystal collimator, comprising two sets of Si(311) double crystals arranged in a dispersive configuration, optionally collimate the DCM (vertically diffracted) beam in the horizontal direction for ultra-SAXS with a minimum scattering vector q down to 0.0004 A−1, which allows resolving ordered d-spacing up to 1 µm. A microbeam, of 10–50 µm beam size, is tailored by a combined set of high-heat-load slits followed by micrometre-precision slits situated at the front-end 15.5 m position. The second set of KB mirrors then focus the beam to the 40 m sample position, with a demagnification ratio of ∼1.5. A detecting system comprising two in-vacuum X-ray pixel detectors is installed to perform synchronized small- and wide-angle X-ray scattering data collections. The observed beamline performance proves the feasibility of having compound features of high flux, microbeam and ultra-SAXS in one beamline.

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S.-W. Lin

Papers

Optical design and performance of the biological small-angle X-ray scattering beamline at the Taiwan Photon Source