BL4-2 Biological Small Angle Scattering/Diffraction

Stopped-flow mixer for Time-Resolved SAXS

A fast stopped-flow mixer is available at BL4-2 for Time-Resolved (TR) solution SAXS experiment. Our high frame rate pixel array detector (Pilatus 300K) and high X-ray flux multilayer monochromator (Mo/B4C multilayer) can be combined in order to achieve fast time-resolution up to 5msec. Our SasTool program is used for reducing the 2D detector images and produces buffer subtracted Intensity vs. q data for each time point of the TR-SAXS measurement. A customized sample injector has been developed to reduce the required sample volume to a minimum of 30ul per shot (standard is currently 50-100ul) eliminating the sample consuming priming of the lines before the measurements. An automatic wash cycle for the sample cell (capillary) is employed after every single shot to ensure that the capillary is clean and no residues remain in the cell from the previous measurement.

Main features:
- Customized Bio-Logic 4 syringe stopped-flow mixer (SFM400) (Fig 1)
- Up to triple mixing using 4 independently-motorized syringes. (Fig 2)
- Temperature controllable.
- Achievable time resolution is 5msec (200Hz frame rate).
- Sample economy: 30-250ul per data set without dead volume (standard is 100ul).
- Variable mixing ratio from 1:1 to 1:100.
- Customizable and powerful cleaning of capillary after every single shot.
- User friendly software for data collection and analysis.

Currently the TR-SAXS experiments require a large investment of time from the BL4-2 staff. If you wish to use the TR-SAXS set up or have any question, please contact BL4-2 staff well in advance of submitting beam time request.

Stopped_flow mixer Flow line

Mounted stopped_flow mixer
Fig 1 Stopped-flow mixer (SFM400) Fig 2 (Top) Flow line (Modified from SFM400 brochure)
Fig 3 (Bottom) Mount on the beam with umbilical link