Nuclear spin hyperpolarization of the solvent using signal amplification by reversible exchange (SABRE)

J Magn Reson. 2015 Aug;257:15-23. doi: 10.1016/j.jmr.2015.04.013. Epub 2015 May 14.


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 (∼20s) to hyperpolarize biomolecules having exchangeable protons. This route may offer future opportunities for SABRE to impact metabolic imaging.

Keywords: Chemical exchange; Hyperpolarization; Iridium catalyst; MR imaging; SABRE; Solvent enhancement.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Catalysis
  • Hydroxyl Radical / chemistry
  • Iridium / chemistry
  • Magnetic Resonance Spectroscopy / methods*
  • Magnetic Resonance Spectroscopy / statistics & numerical data
  • Protons
  • Solvents / chemistry*


  • Protons
  • Solvents
  • Hydroxyl Radical
  • Iridium