Table 2. Adducts Identified as Significant Predictors for Discriminating Between the Contaminated (C) and Reference (R) Sites According to the OPLS-DA Modela.
| putative adduct | precursor ion observed, m/z | product ion observed, m/z | retention time, min | proposed elemental composition of nucleoside adduct | mass accuracy, Δppm | RDB | C/R |
|---|---|---|---|---|---|---|---|
| H483 | 529.2973 | 413.2512 | 10.6 | C22 H44 O12 N2 | 1.1 | 2.0 | ↓ |
| H187 | 406.2178 | 290.1712 | 11.5 | C17 H31 O8 N3 | –1.4 | 4.0 | ↓ |
| L114 | 258.0947 | 142.0477 | 3.30 | C9 H13 O5 N4 | –1.2 | 5.5 | ↑ |
| L127 | 266.0822 | 150.0357 | 8.20 | not determined | ↑ | ||
| H342 | 459.2450 | 343.1968 | 10.3 | C20 H34 O8 N4 | 0.1 | 6.0 | ↓ |
| L129(N6-me-dA) | 266.1242 | 150.0776 | 9.90 | C11 H14 O3 N5 | –2.1 | 7.5 | ↑ |
| H403 | 482.2248 | 366.1769 | 4.50 | C21 H31 O8 N5 | 0.5 | 9.0 | ↓ |
| H368 | 466.2640 | 350.2189 | 14.0 | C20 H33 O5 N8 | –1.4 | 8.5 | ↓ |
| L189 | 291.0887 | 175.0419 | 7.80 | not determined | ↑ | ||
| H264 | 430.1841 | 314.1348 | 10.2 | C18 H27 O9 N3 | 4.8 | 6.5 | ↑ |
| H204 | 411.2129 | 295.1653 | 17.1 | C20 H31 O7 N2 | 0.7 | 6.0 | ↓ |
a
Chemical characteristics assigned to the DNA adducts were the exact mass for the precursor ion (i.e., 2′-deoxyribonucleoside adduct) and the product (nucleobase adduct) ions, [M + H]+ and [(M – dR) + H]+, respectively; the retention time under the employed LC conditions; the proposed elemental composition; mass accuracy (Δppm) determined as a difference between the parent ion mass observed and that calculated using the predicted elemental composition; and the possible number of double bonds (RDB). Upregulated (↑) or downregulated (↓) change in the relative abundance of the adduct as characteristic of the contaminated (C) in relation to the reference (R) group is also shown (C/R).