. Author manuscript; available in PMC: 2021 Mar 23.

Published in final edited form as: Chem Res Toxicol. 2015 Nov 24;28(12):2352–2363. doi: 10.1021/acs.chemrestox.5b00359

Table 3.

Ultra-High-Resolution FT-ICR MS Mass Measurements for Pyrimidine Free Bases Examined in This Study

compound	formula	[M + H]⁺ (theoretical)	[M + H]⁺ (experimental)
thymine	C₅H₆N₂O₂	127.05018	127.05018
5-hydroxymethyluracil	C₅H₆N₂O₃	143.04508	143.04516
5-formyluracil	C₅H₄N₂O₃	141.02948	141.02950
5-carboxyuracil	C₅H₄N₂O₄	157.02438	157.02442
uracil	C₄H₄N₂O₂	113.03458	113.03450
5-methylcytosine	C₅H₇N₃O	126.06618	126.06613
5-hydroxymethylcytosine	C₅H₇N₃O₂	142.06108	142.06108
5-formylcytosine	C₅H₅N₃O₂	140.04548	140.04543
5-carboxycytosine	C₅H₅N₃O₃	156.04038	156.04037
cytosine	C₄H₅N₃O	112.05048	112.05044
¹⁵N₂-5-hydroxymethyluracil	C₅H₆¹⁵N₂O₃	145.03908	145.03920
¹⁵N₂-5-formyluracil	C₅H₄¹⁵N₂O₃	143.02348	143.02356
¹⁵N₂-5-carboxyuracil	C₅H₄¹⁵N₂O₄	159.01838	159.01849
¹⁵N₂-5-hydroxymethylcytosine	C₅H₇N¹⁵N₂O₂	144.05508	144.05518
¹⁵N₂-5-formylcytosine	C₅H₅N¹⁵N₂O₂	142.03948	142.03952
¹⁵N₂-5-carboxycytosine	C₅H₅N¹⁵N₂O₃	158.03438	158.03448