Fig. 3. Determination of F-5caC, F-dC, and F-5mC within mammalian genomes upon feeding of F-5caC by LC-ESI-MS/MS analysis. (a–c) Extracted-ion chromatograms of F-5caC, F-dC, and F-5mC standards. (d–f) Extracted-ion chromatograms of F-5caC, F-dC, and F-5mC detected from genomic DNA of HEK293T cells upon feeding of 300 μM of F-5caC. The peaks of rC + 2 and m5rC + 2 represented the natural isotope peaks of RNA cytidine and 5-methylcytidine, respectively.