Time-resolved solution SAXS (TR-SAXS) is a powerful experimental tool to investigate conformational changes of macromolecular systems and allows to monitor biological processes under near physiological conditions. The time regime for such reactions is generally dependent on the scale of the event and can range from sub-millisecond to hours and beyond. The application of TR-SAXS techniques to structural biology has however been limited mainly due to difficulties with required sample amount and radiation damage. At SSRL BL4-2 we provide prime facilities for biological TR-SAXS experiments on the millisecond time scale and above, putting particular emphasis on overcoming some of the problems of the techniques when applied to biological samples. For this we have developed a small volume stopped-flow mixer optimized for low sample consumption that allows to collect a TR-SAXS data from as little as 30ul of sample. It eliminates the sample consuming priming of the flow lines and prevents premature mixing of the reactant solutions. Furthermore, it automatically cleans the sample cell after each mixing experiment in preparation for the next injection. Together with a high flux multilayer monochromator and a state-of-the-art high frame rate pixel array detector (Pilatus3 X 1M) the TR-SAXS setup at the beam line provides access to reaction kinetics on the millisecond time scale and above. Main features
■ Customized Bio-Logic 4 syringe stopped-flow mixer (SFM400)
■ Semi-automatic data collection and analysis with user friendly software
■ 30-200ul per data set without any dead volume (standard: 100ul)
■ New fast pixel array detector (Pilatus3 X 1M @500Hz)
■ 2 msec time resolution achievable (limited by detector frame rate)
■ Customizable and powerful cleaning of capillary after every single shot
■ Computer-controlled electric rotary valves
■ Each module is temperature controllable
■ Monitor and record mixing signals and timings by oscilloscope
■ High flux beam by Mo/B4C multilayer is available for short exposure
- Extended energy range: 6-17.5keV
- Interchangeable 7 sample-detector distances: 0.25-3.5m
■ Specialized Blu-Ice TR-SAXS tab for TR-SAXS data collection
■ UV port (under development)
BL4-2 Stopped-Fow Mixer Setup
Get beamtime for BL4-2 TR-SAXS
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. Publications of BL4-2 TR-SAXS
Matsui T, Tsuruta H, Johnson JE. Balanced electrostatic and structural forces guide the large conformational change associated with maturation of T = 4 virus. Biophys J. 2010 Apr 7;98(7):1337-43.
Lee KK, Tsuruta H, Hendrix RW, Duda RL, Johnson JE. Cooperative reorganization of a 420 subunit virus capsid. J Mol Biol. 2005 Sep 23;352(3):723-35.
