Table 1 Characterization of the detected nucleoside adducts (A1‒A23), and the 4 unmodified nucleosides, using a HRAM adductomics approach.

Detected nucleosides	Molecular ion, m/z [M]⁺	Specific fragment, m/z [M-dR]⁺	Retention time, min	Identified nucleosides
A1	295.1203	179.0739	3.51
A2	278.1605	162.1126	3.59
dC	228.0978	112.0507	3.81	2′-Deoxycytidine, dC^a
A3	242.1146	126.0664	3.97	5-Methyl-2′-deoxycytidine, 5-me-dC^a
A4	264.0961	148.0484	3.97	Na adduct of 5-me-dC^b
A5	244.0932	128.0457	4.48	5-Hydroxy-2′-deoxycytidine, 5-OH-dC
A6	229.0818	113.0348	5.49	2′-Deoxyuridine, dU
A7	289.1758	173.1288	5.60
A8	268.1043	152.0569	6.41	8-Hydroxy-2′-deoxyadenosine, 8-OH-dA
dA	252.1094	136.0620	6.41	2′-Deoxyadenosine, dA^a
A9	239.1139	123.0667	6.41
A10	274.0915	158.0440	6.42	Na adduct of dA^b
A11	284.1358	168.0883	6.43
A12	300.1299	184.0832	6.43
A13	275.0753	159.0280	7.29	Na adduct of dI^b
A14	253.0931	137.0460	7.30	2′-Deoxyinosine, dI
dG	268.1033	152.0568	7.51	2′-Deoxyguanosine, dG^a
A15	274.1148	158.0676	7.51	Guanidinohydantoin, Gh
A16	290.0852	174.0389	7.52	Na adduct of dG^b
A17	306.0603	190.0129	7.61
T	243.0970	127.0504	7.99	Thymidine, T^a
A18	265.0798	149.0324	7.99	Na adduct of T^b
A19	327.0504	211.0029	8.03
A20	236.1281	120.0809	8.48
A21	284.0989	168.0518	8.75	8-Oxo-7, 8-dihydro-2′-deoxyguanosine, 8-oxo-dG^a
A22	266.1257	150.0777	9.42	N⁶-Methyl-2′-deoxyadenosine, N⁶-me-dA^a
A23	252.1228	136.0759	11.34

Observed mass-to-charge ratio of molecular ion and that of its specific fragment with loss of dR, and retention time under the employed chromatographic conditions are given for each detected nucleoside, along with names of those identified.
For the identified compounds, the mass difference between that observed (reported in this table) and calculated m/z was less than 3 ppm. Empty space indicates adduct not identified.
^aIdentification confirmed by comparison with respective standards.
^bThese were assigned as sodiated adducts of the respective compounds (based on retention time and molecular masses), with molecular ion and specific fragment represented as [M+Na]⁺ and [M-dR + Na]⁺, respectively. All others are assigned as protonated adducts with molecular ion and specific fragment represented as [M + H]⁺ and [M-dR + H]⁺, respectively.

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