High Resolution Tools for Structural Biology

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With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Ryan Julian and his group at the University of California - Riverside are developing methods to improve our ability to determine the structure of proteins - key actors in biology for diverse and important functions that include serving as factories for energy and communications within and among cells. The Julian lab is developing new methods that can reveal the distance between different parts of a protein molecule, providing high resolution structures which contribute to understanding how proteins function and how their function might be manipulated at a molecular level. The primary tool used is mass spectrometry - a rapid technique that can be used with minuscule amounts of sample. Enhanced capabilities for structure determination by mass spectrometry are accelerating our understanding of crucial biological actors. A diverse group of graduate and undergraduate students are carrying out this research and receiving valuable training that will prepare them to push the boundaries of science and technology forward in the future. Dr. Julian and his team are also engaged in outreach efforts targeting high school students from underrepresented groups. The Julian group is developing new approaches to determining high resolution protein structures using energy transfer and covalent crosslinking between specific residues in order to establish multiple, well-defined distance constraints that can be used in conjunction with calculations to yield atomically-defined gas-phase structures. The energy-transfer approach has several key advantages for determination of high resolution structure, including: 1) direct probing of protein substructure, allowing the determination of multiple distance constraints in a single protein; 2) use of native residues for the donor and acceptor, allowing for the installation of any required amino acids by standard site-directed mutagenesis; and 3) extremely selective photochemical cleavage of bonds affording high sensitivity and unambiguous interpretation of the results. Utilizing the speed and sensitivity of mass spectrometry, gas-phase structural biology can tackle proteins not amenable to x-ray crystallography or nuclear magnetic resonance. This research complements and expands the information available from more widely used, lower-resolution approaches. The new methods can be conducted on unmodified, commercially available instruments, increasing the accessibility of high-resolution measurements.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.