Para-hydrogen induced polarization of amino acids, peptides and deuterium–hydrogen gas

Abstract

Signal Amplification by Reversible-Exchange (SABRE) is a method of hyperpolarizing substrates by polarization transfer from para-hydrogen without hydrogenation. Here, we demonstrate that this method can be applied to hyperpolarize small amounts of all proteinogenic amino acids and some chosen peptides down to the nanomole regime and can be detected in a single scan in low-magnetic fields down to 0.25 mT (10 kHz proton frequency). An outstanding feature is that depending on the chemical state of the used catalyst and the investigated amino acid or peptide, hyperpolarized hydrogen–deuterium gas is formed, which was detected with ¹H and ²H NMR spectroscopy at low magnetic fields of B₀ = 3.9 mT (166 kHz proton frequency) and 3.2 mT (20 kHz deuterium frequency).