Benchtop Q-Band Pulsed EPR Spectrometer for Intermolecular Distance Measurements

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Project Summary / Abstract Complex bio-macromolecules such as membrane proteins play crucial roles in many cellular and physiological processes and specific defects are associated with many known. Determining their three- dimensional structures is one of the main objectives in structural biology and the NIH devotes considerable resources towards this goal. In recent years, pulse EPR spectroscopy, in particular Double Electron-Electron Resonance (DEER) has contributed valuable structural constraints to solve structures of bio-macromolecules. However, currently these methods are only available to experts in the field because operating the complex instrument requires lots of training making it difficult for a non-EPR expert to access this highly valuable information. State-of-the-art spectrometer configurations may be the most versatile option; however, many features of current commercially available systems are unnecessary or simply confusing. Options such as continuous wave (cw) EPR are unnecessary when the main objective is to measure distances. In addition, it is also often overwhelming to applications scientist that are not experts in pulsed EPR spectroscopy. Much of the experiment setup and processing can be standardized but current commercial instruments don’t come with these streamlined features. With DEER becoming more popular it is time to propose a solution that is geared specifically towards distance measurements rather than offering a universal research instruments. Removing unnecessary options and focusing only on DEER spectroscopy will allow us to design a compact, turn-key instrument. In this SBIR application we propose to develop a compact, turn-key Q-band pulsed EPR spectrometer for pulsed dipolar spectroscopy. The system will feature a liquid cryogen-free magnet and cryostat, a low-Q but high-sensitivity resonator and a compact, EPR bridge with state-of-the-art pulse shaping capabilities. The system will be fully computer controlled and easy to operate with minimal training. The successful development of this compact, Q-band pulsed EPR spectrometer will provide researchers access to turn-key instrumentation allowing them to easily incorporate experiments such as DEER in their research. This will greatly proliferate the method and is of large interest to many projects funded by the U.S. National Institutes of Health.