Nuclear-Spin Hyperpolarization of Biomolecules by Optically Enhanced NMR at Ultra-High Field

Nuclear magnetic resonance (NMR) is a powerful tool to elucidate molecular structure and dynamics at atomic resolution. Yet, the NMR analysis of biomolecules is often curtailed by low sensitivity and high spectral congestion. High magnetic field strengths (B ₀) are in principle capable of overcoming the above limitations. Even at the highest attainable fields, however, unfavorable hardware-, spin-relaxation- and dielectric-related challenges attenuate the attainable sensitivity. Here, we circumvent the above limitations by synergistically combining data collection at 1.1 GHz (25.9 T) with NMR hyperpolarization in liquids. This strategy enables the analysis of aromatic amino acids and proteins at ultra-high sensitivity and resolution. Systematic comparisons between data collected at 1.1 GHz and 600 MHz reveal advantages and disadvantages of both conditions. Hyperpolarization via low-concentration photochemically induced dynamic nuclear polarization (LC-photo-CIDNP) was applied to small-molecule and macromolecular model systems, that is, two tryptophan (Trp) isotopologs and the ¹³C,¹⁵N-labeled SH3 protein. We show that LC-photo-CIDNP at 1.1 GHz provides both excellent sensitivity (ca. up to 160-fold enhancements relative to non-LC-photo-CIDNP conditions) and remarkable spectral resolution. In all, our results highlight the combination of LC-photo-CIDNP hyperpolarization and ultra-high field as a powerful strategy for the atomic-resolution analysis of biomolecules in solution at low-μM concentration.