Nuclear spin hyperpolarization boosts NMR sensitivity but typically requires complex infrastructure. Signal Amplification by Reversible Exchange (SABRE), a parahydrogen-based hyperpolarization technique, can be conducted using a remarkably low-cost polarizer (<100) comprising only magnetic coils and a standard PC sound card, avoiding magnetic shielding. However, under these conditions SABRE requires direct spin-coupling between parahydrogen and the target nucleus, limiting its application to distant heteronuclear spins such as ⁷⁷Se in biologically relevant selenium-nitrogen heterocycles (e. g. antioxidant, antiviral, and anticancer agents). Here, we overcome the distance restrictions by developing the ¹⁵N-mediated polarization transfer driven by optimized oscillating magnetic fields of the audio frequency. This enables a significant ⁷⁷Se NMR signal enhancement of 11, 600-fold at 9. 4 T in a shielding-free setup within several seconds, corresponding to over 6% of net 77Se polarization. Thus, our approach makes hyperpolarized ⁷⁷Se NMR widely accessible for biomolecular investigations.
Markelov et al. (Mon,) studied this question.