BPS2026 – Nuclear-spin hyperpolarization of biomolecules on an 80 MHz benchtop NMR spectrometer

Liquid-state nuclear magnetic resonance (NMR) provides atomic-level insights into biomolecular structure and dynamics and is suitable for analysis under physiologically relevant conditions. NMR, however, suffers from inherently low-sensitivity, requiring expensive spectrometers, high sample concentrations and long experimental times. A recently developed magnetic-resonance technology known as low-concentration photochemically induced dynamic nuclear polarization (LC-photo-CIDNP) enabled overcoming the above limitations in liquids. LC-Photo-CIDNP involves photoexcitation of a photosensitizer by a LED or LASER, followed by intersystem crossing, collision, and electron transfer with the molecule of interest, triplet-singlet mixing and radical termination to generate nuclear-spin hyperpolarized molecules. The process is conducted in the presence of oxygen scavengers and photosensitizer dyes with a long triplet-state lifetime. Proton LC-photo-CIDNP of amino acids on benchtop NMR spectrometers has so far been limited to D 2 O media and high μM sample concentrations. Here, we show that, by using a 1.88 T low-field NMR spectrometer, higher enhancement values can be obtained via LC-Photo-CIDNP relative to a 14 T NMR spectrometer. This advance highlights the promise of LC-photo-CIDNP for applications involving benchtop NMR spectrometers. Using the 13 C-RASPRINT, a 1 H-detected- 13 C Photo-CIDNP pulse sequence, we detected 2 μM Quasi-Isolated Spin Pair (QISP) tryptophan, with an enhancement factor of ∼3,400. We also developed 1 H-PASS-WET, a 1 H-WET LC-Photo-CIDNP pulse sequence and were able to detect 5 μM natural-abundance tryptophan in H 2 O with an enhancement factor of ∼1,100. Further, we were able to readily detect epinephrine at 250 nM levels. Using the above pulse sequences as well as 1 H-PASSWORD, a CPMG-WET solvent-suppression scheme integrated within an LC-Photo-CIDNP pulse sequence, we obtained robust performance in protonated solvents, complex cell-like media, and unaltered biofluids. These advances bring optically enhanced benchtop NMR within the realm of standard laboratory settings, enabling it to effectively compete with high-field NMR spectrometers.