BioSAXS Essentials 8 workshop introduces state-of-the-art density program

Richard Gillilan, MacCHESS, Cornell University

In an era when our most detailed pictures of biomolecules come from frozen or crystalline samples, biological small angle X-ray solution scattering (BioSAXS) is more essential than ever as a tool for learning how molecules actually behave under realistic biological conditions in the liquid state.

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The 8th BioSAXS Essentials training workshop held April 12-15 drew 36 students, some from as far away as Puerto Rico, Estonia and Korea. In addition to lectures, the students got hands-on experience collecting data at two CHESS stations configured with the latest robotic sample-loading and inline size-exclusion chromatography systems.

Our 8th BioSAXS Essentials training workshop drew a wide-ranging and enthusiastic crowd of 36 students, including 6 from University of Puerto Rico, 1 from Korea, 2 from Estonia and 1 from Canada. About half of the students had never collected data at a synchrotron before!

Part of the attraction of our BioSAXS Essentials course is the hands-on experience. We provide two identically equipped beamlines complete with the latest robotic sample loading and inline size-exclusion chromatography systems. Because of the short down period this past Spring, we had to set up TWO SAXS stations at the same time: G1 and F1 (F1 from an empty hutch) in just a week and a few days. That this kind of thing can be accomplished is one of the unique strengths of CHESS: to rapidly reconfigure experimental stations.

I began the course with a big-picture overview and essential basic physics. Kushol Gupta (UPENN, Perelman School of Medicine) gave a lecture on the practical aspects of how to plan a visit and perform experiments. Thomas Grant (Hauptman Woodward Institute) discussed conventional techniques for constructing molecular envelopes. Steve Meisberger (Princeton) and Kushol Gupta covered some advanced topics such as inline size exclusion chromatography and atomistic modeling.

The most exciting topic we brought to students this year was the new method called “DENSS” devised by Thomas Grant for calculating true electron density from SAXS data. The method was published early this year in Nature Methods, and Jesse Hopkins (now at BioCAT, Advanced Photon Source) worked with Thomas to implement it in our widely used data processing software RAW.  As a result, we were able to get this state-of-the-art density program into the hands of students shortly after it hit the press.  Conventional BioSAXS envelopes are just that: hollow envelopes that give only the exterior shape of the molecule. With DENSS, you can literally see structure inside the shape.

Jesse, Thomas and Steve conducted a tutorial session Saturday morning before students started their hands-on data collection sessions later in the day. Data collection at the two stations ran around the clock until Sunday evening. Many thanks to the speakers and especially our CHESS/MacCHESS team for making this 8th BioSAXS Essentials a success.

To obtain RAW, visit http://bioxtas-raw.readthedocs.io/en/latest/index.html

For more information on DENSS, visit http://denss.org/

True electron density derived from BioSAXS data using the new DENSS algorithm devised by Thomas Grant (HWI). In a Saturday morning tutorial, students learned how to apply this state-of-the-art technique to their own data. DENSS is implemented in our widely used RAW data processing software. [PDB ID 4FE9, image courtesy of Thomas Grant]