1-Methylxanthine-13C4,15N3
1-Methylxanthine-13C4,15N3 is the 13C-labeled and 15N-labeled 1-Methylxanthine. 1-Methylxanthine, a caffeine derivative, is an essential human urinary metabolite of caffeine and theophylline (1,3-dimethylxanthine, TP). 1-Methylxanthine enhances the radiosensitivity of tumor cells.