Figure 4. Analysis of ¹⁵N₁-cholamine tagged carboxyl groups in human lung adenocarcinoma A549 cells and mouse PDX liver tissue extracts.

[¹³C₆]-glucose treatment, polar extraction, and NMR experiment setups were as described in the Experimental Section. A) High resolution 2D ¹H{¹⁵N}-HSQC spectrum of ¹⁵N₁-cholamine derivatized extract of A549 cells cultured in [¹³C₆]-glucose enriched DMEM media. Peak assignments are shown in Table S1. Ala (4), lactate (18), Glu (5), and Gly (8) peaks showed signature splitting patterns in the N dimension, which confirms ¹³C labeling at the carboxylate (C1) and/or the neighboring carbon (C2) in these metabolites. B) High resolution 2D ¹H{¹⁵N}-HSQC spectrum of ¹⁵N₁-cholamine derivatized extract of PDX mouse liver tissue after liquid diet administration of ¹³C₆-glucose. Lactate, alanine, glutamate, glutamine, GSH/GSSG showed ¹³C enrichment in the N dimension. C) The first increment of HNCO experiment in the HCO plane of the PDX mouse liver tissue extract reacted with ¹⁵N₁-cholamine. It confirmed ¹³C labeling at the carboxylate group of these metabolites . D) The first increment of HNCO experiment in the HN plane of the PDX mouse liver tissue extract reacted with ¹⁵N₁-cholamine, confirming ¹⁵N labeling in these metabolites.