Li, Siyu, Shibani Bhattacharya, Ching-Yu Chou, Minglee Chu, Shu-Cheng Chou, Marco Tonelli, Michael Goger, Hanming Yang, Arthur G. Palmer, and Silvia Cavagnero. “LC-Photo-CIDNP Hyperpolarization of Biomolecules Bearing a Quasi-Isolated Spin Pair: Magnetic-Field Dependence via a Rapid-Shuttling Device.” Journal of Magnetic Resonance 359 (February 1, 2024): 107616.
https://doi.org/10.1016/j.jmr.2023.107616.
Liquid-state low-concentration photochemically induced dynamic nuclear polarization (LC-photo-CIDNP) is an emerging technology tailored to enhance the sensitivity of NMR spectroscopy via LED- or laser-mediated optical irradiation. LC-photo-CIDNP is particularly useful to detect solvent-exposed aromatic residues (Trp, Tyr), either in isolation or within polypeptides and proteins. This study investigates the magnetic-field dependence of the LC-photo-CIDNP of Trp-α-13C-β,β,2,4,5,6,7-d7, a Trp isotopolog bearing a quasi-isolated 1Hα-13Cα spin pair (QISP). We employed a new rapid-shuttling side-illumination field-cycling device that enables ultra-fast (90–120 ms) vertical movements of NMR samples within the bore of a superconducting magnet. Thus, LC-photo-CIDNP hyperpolarization occurs at low field, while hyperpolarized signals are detected at high field (700 MHz). Resonance lineshapes were excellent, and the effect of several fields (1.18–7.08 T range) on hyperpolarization efficiency could be readily explored. Remarkably, unprecedented LC-photo-CIDNP enhancements ε ≅ 1,200 were obtained at 50 MHz (1.18 T), suggesting exciting avenues to hypersensitive LED-enhanced NMR in liquids at low field.