Figure 4.

(a) Formation of ¹³C-hyperpolarized fumarate. Acetylene dicarboxylic acid [1-¹³C] disodium salt labeled as molecule ADCA reacts with parahydrogen in the presence of sodium sulfite and the catalyst in D₂O. The reaction results in a production of disodium [1-¹³C]fumarate, molecule FUM, with the two protons in a singlet state. Application of the S2hM pulse sequence converts the singlet state into observable ¹³C magnetization FUM*. (b) 90-S2hM pulse sequence used to transfer the polarization from the proton singlet state to carbon. (c) The J-coupling network of [1-¹³C]fumarate. The J-coupling values were taken from ref (43).