Fig. 2.

RD-DNP time courses acquired following injection of hyperpolarized [2-¹³C]methylglyoxal into a suspension of RBCs. a ¹³C NMR spectra obtained upon injection of 1 mL of hyperpolarized [2-¹³C]MeGx into 3 mL of RBCs (hematocrit, Ht, of 52%) in phosphate-buffered saline giving a final concentration of 1.3 mM. Spectra were acquired every 1 s. *Denotes position of spectral artifact that was edited out. b Expansion of the 200-215 ppm region of the bottom spectrum in shown in a. c ¹³C NMR peak intensities of the four main species in spectra acquired following injection of different concentrations of [2-¹³C]MeGx into suspensions of RBCs (final Ht values 39–40%). Data points were scaled so that the initial sums of the peak amplitudes of MGMH and MGBH were equal to the nominal concentrations of injected MeGx. The solid lines are nonlinear least squares fits of numerical solutions of the array of differential equations. Abbreviations: D-Lac, [2-¹³C]D-lactate; HTA, hemithioacetal of [2-¹³C]MeGx; MG, the ketoaldehyde form of [2-¹³C]MeGx; MGBH, the bishydrate of [2-¹³C]MeGx; MGMH, the monohydrate of [2-¹³C]MeGx; SLG, [2-¹³C]S-D-lactoylglutathione; DMSO, natural abundance ¹³CD₃ in the dimethylsulfoxide-d6 used to make up the hyperpolarization solution