High-Field Magic-Angle Spinning Electron Paramagnetic Resonance

ongoing

Dynamic Nuclear Polarization (DNP) is the most widely applicable method for solving the main problem of nuclear magnetic resonance (NMR): its low sensitivity. This is achieved by polarization transfer from electron spins to nuclear ones, allowing for up to two orders of magnitude signal enhancement, which enabled the expansion of NMR to multiple systems previously unamenable to it. Despite two decades of extensive research, DNP is yet to reach its full potential, the bottleneck being the quantum-mechanical understanding. While Electron Paramagnetic Resonance (EPR) experiments have provided multiple insights on static DNP mechanisms, leading to improved DNP experiments, analogous EPR experiments for Magic Angle Spinning (MAS)-DNP, the most prolific DNP variant, were never performed. Instead, our understanding of MAS-DNP relies on theoretical considerations and numerical simulations, which naturally cannot capture the entire picture. The main obstacle for MAS-EPR is the complexity of the instrumentation and lack of methodology to perform EPR experiments under characteristic MAS-DNP conditions: high magnetic fields, cryogenic temperatures, and MAS. This project aims to bridge this crucial gap. We have recently recorded the first high-field MAS-EPR spectra, using a unique high-field dual DNP/EPR spectrometer specifically tailored to the investigation of DNP mechanisms, designed and constructed in my lab. In this project, we will expand the experimental capabilities by developing the dedicated hardware and establishing the methodology for high-field, cryogenic MAS-EPR. This will allow, for the first time, to experimentally observe the electron spin dynamics in MAS-DNP, thus deciphering the DNP mechanisms. This will unlock the full potential of MAS-DNP, allowing for systems currently unamenable to NMR to benefit from the atomic-level structural and dynamical information NMR provides, having profound effects in chemistry, structural biology and material science.