To demonstrate singlet-contrast imaging we acquired images of a hyperpolarized reaction mixture in a 10 mm NMR tube surrounded by H2O. This is shown in Fig. . The imaging was performed in a 7 T magnetic field. The 10 mm NMR tube initially contained fumarase in a deuterated phosphate buffer solution (PBS) at pH 7 (optimal for this reaction ). The precursor solution was hydrogenated with parahydrogen and then injected into the 10 mm NMR tube for imaging. Further experimental details are given in the Materials and Methods section.