Figure 2

2-D ¹H TOCSY identification of polar metabolites in the lung tumor tissue of patient #6. The 2-D TOCSY contour map is displayed along with the corresponding 1-D high-resolution spectrum. Panels A, B and C, D show the 0.8–6.4 and 5.7–9.5 ppm regions of the spectra, respectively. The assignment of cystine residue of oxidized glutathione (GSSG) was illustrated, which was based on the ¹H covalent connectivity (traced by solid rectangles) and chemical shifts (traced by dashed blue lines). Lactate was discerned similarly and based on the peak splitting pattern (doublet for 3-methyl @ 1.32 ppm and quartet for 2-methine protons @ 4.11 ppm). In addition, the ¹³C satellite cross-peaks of 3-methyl and 2-methine protons of lactate (patterns 1 and 2) and Ala (patterns 3 and 4) were evident (traced by dashed green rectangles), and the peak pattern indicates that lactate and Ala were uniformly ¹³C labeled [19]. The ¹³C satellite cross-peak patterns for the protons of Glu (5, 6, 12, 20), Gln (9), glutamyl residue of oxidized glutathione (GSSG) (7, 10, 13) and Asp (16–19) were present and noted by vertical and horizontal dashed green lines. The ¹³C satellite cross-peaks 14 and 15 were contributed by a mixture of ¹³C-2-Glu, ¹³C-2-Gln, and ¹³C-2-Glu of reduced glutathione (GSH).