HIGH-SENSITIVITY NMR AT ROOM TEMPERATURE FOR MOLECULAR STRUCTURE AND DYNAMICS

Washington University, Saint Louis MO

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Abstract

? DESCRIPTION (provided by applicant): This research proposes to develop solid state Dynamic Nuclear Polarization (DNP) to achieve NMR signal enhancements of >200 at room temperature, representing a significant advancement over currently employed DNP spectrometers operating at 100 Kelvin. Solid state NMR is well suited to probe atomic level structure and molecular dynamics of membrane proteins and amyloid fibrils. However, low inherent sensitivity limits solid state NMR measurements. Sensitivity from electron paramagnetic resonance (EPR) can be transferred to NMR to boost signals by more than two orders of magnitude in a process known as DNP. These ultrasensitive DNP experiments currently require samples to be frozen to below 100 Kelvin. Performing NMR based structural biology at cryogenic temperatures has significant drawbacks including perturbing molecular structure and a loss of spectral resolution. We propose to implement DNP at room temperature with new fast frequency tuning microwave sources (gyrotrons) to enable time domain DNP. These new gyrotrons will have an irradiation bandwidth of >600 MHz compared to currently available sources of 1 MHz, resulting in much better EPR control. We will also design new microwave resonance structures to improve microwave penetration, while reducing microwave heating. The new DNP technology and methodology will be demonstrated with structural and molecular dynamic studies of activators bound to Protein Kinase C regulatory domains. Achieving NMR sensitivity gains of >200 at room temperature will greatly expand the scope and precision of NMR based structural biology.