BioSAXS Beamline

The BioSAXS beamline is a high-flux beamline dedicated to solution small angle scattering experiments at the Australian Synchrotron. BioSAXS is part of the BR-GHT suite of beamlines and has recently entered user operations in cycle 2023/3. The primary role of the beamline it to take 2D small angle scattering patterns on solution samples, either equilibrated or evolving, using a Pilatus3S 2M area detector. The aim of the beamline is to provide a streamlined and largely automated experience, from sample presentation to data capture and processing.

Beamline Technical Details

Source

BioSAXS has a superconducting undulator source, providing an X-ray beam of flux on the order of 10¹⁴ photons/s at the sample position. The undulator is optimized for a photon energy of 12.0 keV and this will be the primary photon energy used for experiments. If you require other photon energies, please discuss this with the beamline team prior to submitting your proposal as your experiment may be more suited to the SAXS/WAXS beamline, on which the undulator has a wider accessible energy range.

Monochromator

The use of a double multilayer monochromator increases the flux relative to a standard double crystal monochromator. The multilayer on BioSAXS comprises B₄C/Mo layers and an energy bandpass (dE/E) of 1.0%. As a result, BioSAXS is not suited to anomalous SAXS experiments, which rely on finer energy resolution. If you wish to perform anomalous SAXS measurements, please reach out to the SAXS/WAXS beamline team to discuss your requirements.

Detector

BioSAXS has a Pilatus3X 2M detector, similar to that deployed on the SAXS/WAXS beamline. The detector is mounted on a translation stage in a large vacuum vessel, allowing it to reach distances of ~700-7000 mm from the sample position. With a photon energy of 12.0 keV, this should allow a minimum q of ~0.003 Å^-1 at the longest sample-detector distance and a maximum q of ~2.4 Å^-1 at the shortest sample-detector distance.

Sample Environments

The beamline can currently support the following sample environments:

Coflow [sample autoloader with batch mode & size exclusion chromatography (SEC) mode]

For automated loading of solution-based samples into a flow-through capillary setup with coflow. In a coflow setup, a sheath of buffer/water is simultaneously pumped through the capillary to surround the sample being presented to the beam to reduce radiation damage. (For more details, refer to Kirby, N. et al. Acta Crystallogr., Sect. D: Biol. Crystallogr. 2016, 72, 1254 & Ryan, T. M. et al. Appl. Crystallogr. 2018, 51, 97.) Coflow will operate in two modes: Batch mode and in-line Size exclusion chromatography (SEC) mode. Please indicate which mode(s) are required in your proposal.

• Batch mode – For measurements on equilibrated samples. Samples are presented in 96 well plates (volume up to 100 µL). Corresponding sheath buffers/solvent are loaded in Schott bottles (100 mL – 1 L). The buffer/solvent is loaded into the top of the Coflow cell, which is drawn through the measurement capillary as the sample is injected to act as the sheath fluid.

• SEC mode – For measurements requiring separation of components in solution by size. Samples are presented in 96 well plates (volume up to 100 µL). Buffers/eluent are loaded into Schott bottles and circulated through a column by an HPLC pump and through the Coflow capillary by separate pumps. Samples are loaded into the column loop and the eluent from the column flows through the Coflow cell with sheath fluid surrounding the eluent flow. Significant volumes of buffer are required to supply the HPLC pump and the coflow sheath fluid (100 mL - 1 L). UV-detection close to the Coflow cell gives a secondary indication of sample elution. Column containment accepts standard 5-150 columns (3 mL bed volume) and the larger 10-300 columns (24 mL bed volume). We advise that users supply their own clean columns and have tested their elution protocol prior to attending the beamline.

• Please note that the Coflow is compatible with fully liquid samples only, no solids/gels/precipitates will be compatible with the Coflow. If your samples contain solids, precipitates, or are viscous please contact the beamline team to discuss your experiments. In the first instance, we will direct you to the most appropriate alternative sample environments to perform your experiments.

Open

Capillary Rack

Capillary rack with 9 positions that will take standard 1.5 mm diameter capillaries (sample volume 80-200 µL) available from Hilgenberg/Charles Supper. Users are expected to supply their own capillaries for measurements using the capillary rack and the beamline team can supply the contact details of the relevant suppliers. Each capillary position is heated by a peltier element, providing temperature control within temperature ranges for standard measurements in aqueous solution (5-80 °C). Temperature-ramp schemes are programmable in sequence with data acquisition.

Open

Linkam Stage

A temperature-controlled stage with a single capillary position that takes standard 1.5 mm diameter capillaries (sample volume 80-200 µL) available from Hilgenberg/Charles Supper. Users are expected to supply their own capillaries. The Linkam Stage provides a wider temperature range, of up to 350 °C, for the measurements of fluid samples. Temperature-ramp schemes are programmable in sequence with data acquisition. The position of the capillary can be moved vertically to the beam during an acquisition sequence, enabling data collection at multiple positions along the sample.

Flowthrough Capillary

For dynamic measurements on evolving systems circulated through a capillary using a peristaltic pump. Sample volumes will need to be on the order of 15-20 mL to ensure sufficient volume for circulation though the capillary. Multiple modes of operation are possible with this sample environment including:

• Free-hanging capillary – Capillary in the X-ray beam under ambient hutch conditions.

• Temperature-controlled capillary – Capillary mount under temperature control by circulating water bath.

The following sample environments will be added to proposal spreadsheets as they are fully commissioned:

Flowthrough Capillary Extensions

• CHROLIS light source – Capillary mount under temperature control and with secondary illumination perpendicular to the X-ray beam by UV-Vis-NIR LEDs. Details on the illumination wavelengths available are given below.

• BYO light source – If you wish to use your own in-house light source (LED, Laser etc.) to stimulate change in a sample, please contact the beamline team immediately at as-biosaxs@ansto.gov.au. Appropriate arrangements will need to be made with the synchrotron safety team before a user-supplied light source will be allowed to be used on site. The best time to confirm this is before submitting your proposal, otherwise we cannot guarantee the technical feasibility of your experiment.

BioSAXS has a Thorlabs CHROLIS-1 6-wavelength high-power LED source fitted with the following LEDs coupled into a liquid light guide. Details below are sourced from the CHROLIS-1 manual supplied by Thorlabs and the spectra below are from the Thorlabs website.

Stopped-flow Measurements

For fast time-resolved studies on evolving samples using BioLogic SFM-4000 Stopped-flow with an X-ray observation head. Four syringes allow for up to four different solutions, with a minimum volume of 10 ul from each syringe, to be injected into the capillary at adjustable flow rates, volumes, and ratios. The capillary sits in the observation head, with a 60° opening for SAXS measurements. The mixed sample can be rapidly captured by SAXS with a dead time of only 0.7 ms. Note that the current dead volumes inside the stopped flow unit require there to be 100s µL of sample prepared and as such this class of measurement will not be suited to experiments where <1 mL of sample can be prepared.

In Situ Magnetic Fields

For measurements on samples susceptible to magnetic fields in solution.

Shear Cell

For oriented SAXS measurements on anisotropic samples in solution, sheared with the velocity gradient parallel to the X-ray beam.

Rheometer [Not to be utilised on BioSAXS]

Initial testing of the Anton Paar rheometer on the SAXS/WAXS beamline has revealed that the high levels of flux on BioSAXS are likely to cause irreparable damage to the plastic sample cells the unit was supplied with. As such, the rheometer will not be offered on BioSAXS and users wishing to perform rheo-SAXS measurements should submit their proposals to the SAXS/WAXS beamline.

Should I apply for BioSAXS or SAXS/WAXS beamtime in 2024 round 3? 

• For solutions that are automatically loaded please apply for BioSAXS beamtime where the Coflow Autoloader is used. Exceptions include samples or experiment design not feasible for BioSAXS (such as anomalous scattering, photon energy requirement (>15 KeV), high viscosity, etc.) for which the SAXS/WAXS beamline will maintain a limited capability for automatic liquid handling.    

• SEC-SAXS for proteins should be on BioSAXS 

• Batch measurements for samples in solution should typically be on the BioSAXS beamline 

• Solution samples in static capillaries can be used on BioSAXS or SAXS/WAXS 

• Rheo-SAXS proposals should be directed to the SAXS/WAXS beamline

• Contact staff at as-scattering@ansto.gov.au for guidance on specific experiment plans and beamline suitability