A University of Chicago graduate student in Biophysical Sciences has received the 2018 Rosalind Franklin Investigator Award from the Advanced Photon Source (APS) Users Organization at the U.S. Department of Energy’s (DOE) Argonne National Laboratory.

Joshua Riback, who is in his fifth year of graduate studies, was recognized for his work using small-angle X-ray scattering (SAXS) techniques at the APS to study biophysical interactions.

Riback’s research focuses on the link between the biophysical properties of macromolecules and the principles of biological phenomena, such as subcellular localization and compartmentalization, evolution and fitness. By focusing on how proteins respond when temperature increases, Riback is working toward understanding the breadth of mechanisms that occur in the temperature-dependence and specificity of protein assembly.

“I was quite amazed at the work being done at the synchrotron, especially how many different techniques by many different fields seem to be taking part at the same time.” — Joshua Riback, University of Chicago graduate student and APS user

Ultimately, the goal is to extrapolate these mechanisms to other biological signals or stresses, so as to develop our understanding of the physical basis and cellular benefits of assembly.

Riback first worked on a light source during his first year as a graduate student, an experience that opened his eyes to how the tool can be applied by so many different scientific disciplines. A synchrotron produces very powerful, bright X-rays that can probe matter up to the atomic level. Up to 60 different experiments can be done at the same time at the APS, a DOE Office of Science User Facility.

“I was quite amazed at the work being done at the synchrotron, especially how many different techniques by many different fields seem to be taking part at the same time,” he said.

Riback’s research has so far resulted in two ground-breaking papers that utilized and advanced the application of SAXS, using the BioCAT beamline at the APS. The first is “Stress-triggered phase separation is an adaptive, evolutionarily tuned response.” In it, Riback and the team demonstrated the reconstitution of a physiologically relevant phase separation process in vitro under physiological conditions, a first. Using SAXS at the APS, his results connected the unusual biophysical properties of a specific molecule to the cell’s capacity to grow during stress, a major advance for the field.

The second paper, published in Science, “Innovative scattering analysis shows that hydrophobic disordered proteins are expanded in water,” developed a new method to extract the dimensions of disordered proteins and the strength of intra-protein interactions from a single SAXS measurement. The information contained within SAXS experiments is often difficult to extract. This is especially true for polymers, including intrinsically disordered proteins (IDPs), where data are fit with analytical functions assuming a Gaussian random walk developed decades ago. But by using the advantages provided by the APS (namely, elimination of aggregates and improper subtraction and high signal to noise as a result of the high intensity of the APS) — coupled with advances in computation — Riback and team developed a molecular form factor to quantify the properties of polymers including size and shape.

APS officials said Riback’s analysis procedure resolves the challenge of how to accurately extract gyration and solvent quality for disordered proteins and polymers. The application of Riback’s new analysis to a set of three IDPs challenged the widely held view that the unfolded states of proteins are collapsed globules under physiological conditions. Although these three IDPs have low-net charge and hydrophobicity typical of well-folded proteins, each is highly expanded in the absence of denaturant.

The combination of Riback’s high-data quality, obtained using the state of the art SEC-SAXS setup at BioCAT, and new analysis procedure were so strong that his publication was accepted by Science on the first submission, and Riback’s SAXS analysis method already is becoming the standard in the field.

Riback received his bachelor’s degree in Biophysics from The Johns Hopkins University. His thesis work is under the dual mentorship of Allan Drummond and Tobin Sosnick. A native of Livingston, N.J., he will soon become a postdoctoral researcher at the Brangwynne lab at Princeton University.

This was adapted from an Argonne National Lab press release