Proton signal enhancement of three orders of magnitude in high-field liquid-state NMR.

Safiullin, Kajum; Zasukhin, Dmitrii; Minaei, Masoud; Kouřil, Karel; Janssen, Gerrit E; Kentgens, Arno P M; Meier, Benno · Nat Commun · 2026

basic_science · Level V

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Abstract

Dissolution-dynamic nuclear polarization (d-DNP) is a hyperpolarization technique that is used to enhance the sensitivity of liquid-state nuclear magnetic resonance (NMR) in biophysical and chemical applications. D-DNP is used widely for the sensitivity enhancement of hetero-nuclei such as <sup>13</sup>C, but it is barely used for <sup>1</sup>H hyperpolarization, despite the abundance of <sup>1</sup>H in organic matter. Here we show that OX063, a radical that has so far been used only for the hyperpolarization of low-γ nuclei such as <sup>13</sup>C, may be used also to hyperpolarize <sup>1</sup>H. This hyperpolarization route is enabled by the use of a klystron amplifier that provides three orders of magnitude more power than conventionally used solid-state microwave sources. Following hyperpolarization, the sample is ejected from the polarizer and liquefied, yielding <sup>1</sup>H signal enhancements of  ~ 1000 in high-field NMR. The use of OX063 limits not only T<sub>1</sub> relaxation during sample transfer, but we also show that it preserves the liquid-state T<sub>2</sub>, and therefore offers superior sensitivity and resolution. The applicability of this method to polarize <sup>1</sup>H of selected amino acids is demonstrated.