A Resonator for Pulsed ODNP Spectroscopy to Study Surface Hydration Dynamics

Project Summary / AbstractThe proposed research focuses on the development of a turn-key resonator for liquid-state Overhauser Dynamic Nuclear Polarization (ODNP) spectroscopy to study the site-specific translational dynamics of water molecules located at the interface of bio-macromolecules such as membrane proteins. It will allow researchers to readily perform ODNP experiments in either a state-of-the-art commercially available X-band cw/pulsed electron paramagnetic resonance (EPR) spectrometer or using a benchtop ODNP spectrometer.In recent years, DNP has proven to be a robust method to increase signal intensities in NMR experiments in laboratories around the world and substantial progress has been made in adapting DNP for solid- and solution- state NMR spectroscopy. This progress has sparked a new interest in ODNP spectroscopy. Although the method is known since the 1960s it has just recently been applied successfully to study the site-specific translational dynamics of water located at the interface of large bio-macromolecules such as membrane proteins. ODNP can map out the local and site-specific hydration dynamics landscape of membrane proteins and lipid membranes and can provide critical information about the protein structure and dynamics.One of the major challenges in ODNP spectroscopy is microwave induced sample heating. During Phase I of this project, we successfully designed, fabricated and characterized a novel prototype ODNP resonator. This SBIR Phase II application will assure that the prototype can be turned into a customer product. As demonstrated by the prototype, the resonator will have a much higher microwave conversion factor compared to conventional rectangular or circular EPR cavities. In addition, the low Q resonance structure will allow pulsed ODNP experiments to further minimize microwave induced heating by reducing the average power required to saturate the EPR transitions.The successful development of this technology will provide researchers access to instrumentation allowing them to incorporate ODNP spectroscopy in their research routine without the hassle of troubleshooting home-built equipment. This will greatly proliferate the method and is of large interest to many projects funded by the U.S. National Institutes of Health.