B21 operates in a fixed camera length configuration (4.014 meters) at 12.4 keV.
The camera length range is suitable for particles with an Rg < 200 Angstroms.
B21 can measure a resolution range from 0.0038 to 0.42 Å-1 using a flux of ~1011 photons per second and is optimized for solution state SAXS experiments.
We offe two standard data collection methods:
- batch mode data collection using the EMBL Arinax sample handling robot
- size-exclusion chromatography coupled SAXS (SEC-SAXS) using an Agilent HPLC system.
BioSAXS Robot The bioSAXS robot automates a data collection from a user described spreadsheet of samples in either a 96-well plate or a set of PCR strips. Each sample is 30 uL and is stored between 4 and 15 degrees. The samples are loaded into a temperature controlled quartz cell capillary (100 um thick) for X-ray scattering measurements.
Standard bioSAXS experiments using the robot require buffer matching to be performed by the user. For buffer matching, we recommend
- SEC (be sure to collect buffer after 1.2 column volumes have passed)
- spin concentrators
Exposure times vary from 1 to 5 minutes. Very small particles (< 10 kDa) will require extended exposure times.
SEC SAXS at B21 Inline SEC SAXS is provided by an Agilent 1200 HPLC system. We offer several columns that include the 2.4 mL Superdex 200 (GE Healthcare) and the 4.6 mL KW-402, -403 and -404 (Shodex) columns. Superose columns operate at comparatively lower pressures, largely composed of conjugated sugars whereas the Shodex columns are higher pressure columns composed of silica. Samples are measured in a specialized cell with ~500x lower background than the bioSAXS robot cell. Please see PDF for further details regarding column performance and expected dilution.
MALS at B21 B21 operates an 18-angle Wyatt multi-angle light scattering instrument inline with an Agilent HPLC system. Onsite users have access to the instrument, it is fully automated and only requires the user to make a suitable running buffer. The MALS instrument is an excellent, independent method for assessing sample quality through mass and radius-of-hydration estimates.
Wet-Laboratory We provide access to a small wet lab providing room-temperature and refrigerated microfuges, a large centrifuge for spin-concentrators, temperature baths and shakers and an Agilent HPLC for onsite, small-scale purifications. Samples can be stored at -80, -20 and 4 degrees C.
Planned Upgrades B21 will be upgrading our optical components within the next 15 months. In Fall of 2015, we will be installing new scatter-less germanium slits near our beam defining aperture that will lower the instrument’s scatter near the beamstop. Lower background scatter near the beamstop will inable more reliable measurements at low particle concentrations.
In addition, we are changing the monochromator from a double crystal monochromator (DCM) to a double multi-layer crystal monochromator (DMM). The DMM will increase our flux ~90x at the expensive of band-width. The DMM requires a new focusing optic that will be installed at the same time.
During Summer 2015, we will install an innovative automated camera changer, which will allow users to select a camera length of up to 8m, with top and central beamstop positions.