Bacteriophage PR772 X-Ray Free Electron Laser and Cryo-Electron Microscopy Studies

Structural details about viruses and their components are important for understanding the many steps in a virus life-cycle, including entry into host cells, replication, assembly, and release of progeny virions. X-ray crystallography and electron microscopy, including cryo-EM, have been used extensively for virus structural studies. Recent advances with cryo-EM have significantly advanced the field with near-atomic resolution structures of viruses being achievable. X-ray free-electron lasers (XFELs) are a novel, developing method to solve structures for non-crystalline single particle targets like viruses. Diffraction patterns can be collected directly from particles at room temperature. High quality, homogeneous virus preparations are critical for both cryo-EM and XFEL studies. Thus, optimization of virus growth and sample preparation are important steps in virus structural studies. The work described in this thesis focused on optimization of protocols for growth and purification of bacteriophage PR772 for XFEL and complementary cryo-EM studies. PR772 is one of several model viruses used in the single particle initiative (SPI) experiments at the SLAC National Laboratory Accelerator Laboratory Linac Coherent Light Source (LCLS). SPI is a collaborative international effort that works towards identifying and solving challenges of high-resolution single particle imaging using XFELs. Single particle diffraction snapshots were collected from PR772 particles prepared with optimized protocols. PR772 preparations were also used for cryo-EM imaging, with the goal to obtain a high-resolution structure of the virus. The optimization and characterization employed to assure samples suitable for XFEL and cryo-EM are detailed, along with data collected with both approaches.