Abstract
Abstract Here we report the polarization of the solvent OH protons by SABRE using standard iridium-based catalysts under slightly acidic conditions. Solvent polarization was observed in the presence of a variety of structurally similar N-donor substrates while no solvent enhancement was observed in the absence of substrate or para-hydrogen (p-H2). Solvent polarization was sensitive to the polarizing field and catalyst:substrate ratio in a manner similar to that of substrate protons. SABRE experiments with pyridine-d5 suggest a mechanism where hyperpolarization is transferred from the free substrate to the solvent by chemical exchange while measured hyperpolarization decay times suggest a complimentary mechanism which occurs by direct coordination of the solvent to the catalytic complex. We found the solvent hyperpolarization to decay nearly 3 times more slowly than its characteristic spin-lattice relaxation time suggesting that the hyperpolarized state of the solvent may be sufficiently long lived (∼20 s) to hyperpolarize biomolecules having exchangeable protons. This route may offer future opportunities for SABRE to impact metabolic imaging.
Original language | English (US) |
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Article number | 5646 |
Pages (from-to) | 15-23 |
Number of pages | 9 |
Journal | Journal of Magnetic Resonance |
Volume | 257 |
DOIs | |
State | Published - Jun 1 2015 |
Keywords
- Chemical exchange
- Hyperpolarization
- Iridium catalyst
- MR imaging
- SABRE
- Solvent enhancement
ASJC Scopus subject areas
- Biophysics
- Biochemistry
- Nuclear and High Energy Physics
- Condensed Matter Physics