Nuclear hyperpolarization of (1-13C)-pyruvate in aqueous solution by proton-relayed side-arm hydrogenation

Abstract

We employ Parahydrogen Induced Polarization with Side-Arm Hydrogenation (PHIP-SAH) to polarize (1-¹³C)-pyruvate. We introduce a new method called proton-relayed side-arm hydrogenation (PR-SAH) in which an intermediate proton is used to transfer polarization from the side-arm to the ¹³C-labelled site of the pyruvate before hydrolysis. This significantly reduces the cost and effort needed to prepare the precursor for radio-frequency transfer experiments while still maintaining acceptable polarization transfer efficiency. Experimentally we have attained on average 4.33% ¹³C polarization in an aqueous solution of (1-¹³C)-pyruvate after about 10 seconds of cleavage and extraction. PR-SAH is a promising pulsed NMR method for hyperpolarizing ¹³C-labelled metabolites in solution, conducted entirely in high magnetic field.