Table 1.
Interpretation of ESI-IT mass spectra of fractions 3–5 isolated from E. coli R1 LOS preparation.
| Oligosaccharide Structure | Calculated Monoisotopic Mass (Da) | Observed Ion (m/z) | Calculated Ion (m/z) | Interpretation of the Ion |
|---|---|---|---|---|
| Fraction 3 (negative mode) | ||||
| [ECA]3-Glc3-Gal2-Hep3-Kdo-P2 | 3606.12 | 1201.15/nd | 1201.03/1802.05 | [M-3H]3−/[M-2H]2− |
| [ECA]3-Glc3-Gal2-Hep3-Kdo-P3-Etn | 3729.13 | 1242.15/nd | 1242.04/1863.56 | [M-3H]3−/[M-2H]2− |
| [ECA]3-Glc3-Gal2-Hep3-Kdo-P3-Etn | 3729.13 | 1235.81/nd | 1236.03/1854.55 | [M-H2O-3H]3−/[M-H2O-2H]2− |
| [ECA]3-Glc3-Gal2-Hep3-Kdo-P3-Etn | 3729.13 | 1249.47/nd | 1249.36/1874.54 | [M-3H, Na]3−/[M-2H, Na]2− |
| [ECA]3-Glc3-Gal2-Hep3-Kdo-P4-Etn | 3809.10 | 1268.81/nd | 1268.69/1903.54 | [M-3H]3−/[M-2H]2− |
| [ECA]3-Glc3-Gal2-Hep3-Kdo-P4-Etn | 3809.10 | 1276.45/nd | 1276.02/1914.53 | [M-3H, Na]3−/[M-2H, Na]2− |
| [ECA]4-Glc3-Gal2-Hep3-Kdo-P2 | 4213.35 | 1403.53/nd | 1403.44/2105.67 | [M-3H]3−/[M-2H]2− |
| [ECA]4-Glc3-Gal2-Hep3-Kdo-P3-Etn | 4336.35 | 1444.53/nd | 1444.44/2167.17 | [M-3H]3−/[M-2H]2− |
| Fraction 4 (negative mode) | ||||
| [ECA]2-Glc3-Gal2-Hep3-Kdo-P2 | 2998.90 | 998.63/1498.41 | 998.63/1498.44 | [M-3H]3−/[M-2H]2− |
| [ECA]2-Glc3-Gal2-Hep3-Kdo-P2 | 2998.90 | 992.63/1489.39 | 992.62/1489.44 | [M-H2O-3H]3−/[M-H2O-2H]2− |
| [ECA]2-Glc3-Gal2-Hep3-Kdo-P3-Etn | 3121.91 | 1039.63/1559.91 | 1039.63/1559.95 | [M-3H]3−/[M-2H]2− |
| [ECA]2-Glc3-Gal2-Hep3-Kdo-P3-Etn | 3121.91 | 1033.63/1550.88 | 1033.62/1550.94 | [M-H2O-3H]3−/[M-H2O-2H]2− |
| [ECA]2-Glc3-Gal2-Hep3-Kdo-P4-Etn | 3201.88 | 1066.28/nd | 1066.28/1599.93 | [M-3H]3−/[M-2H]2− |
| [ECA]3-Glc3-Gal2-Hep3-Kdo-P2 | 3606.12 | 1201.02/nd | 1201.03/1802.05 | [M-3H]3−/[M-2H]2− |
| [ECA]3-Glc3-Gal2-Hep3-Kdo-P3-Etn | 3729.13 | 1242.00/nd | 1242.04/1863.56 | [M-3H]3-/[M-2H]2− |
| Fraction 5 (negative or positive mode) | ||||
| [ECA]-Glc3-Gal2-Hep3-Kdo-P2 | 2391.68 | 796.25/1194.81 | 796.22/1194.83 | [M-3H]3−/[M-2H]2− |
| [ECA]-Glc3-Gal2-Hep3-Kdo-P2 | 2391.68 | 790.22/1185.80 | 790.21/1185.82 | [M-H2O-3H]3−/[M-H2O-2H]2− |
| [ECA]-Glc3-Gal2-Hep3-Kdo-P3 | 2471.64 | 822.89/1234.81 | 822.87/1234.82 | [M-3H]3−/[M-2H]2− |
| [ECA]-Glc3-Gal2-Hep3-Kdo-P3-Etn | 2514.69 | 837.25/1256.31 | 837.22/1256.34 | [M-3H]3−/[M-2H]2− |
| [ECA]-Glc3-Gal2-Hep3-Kdo-P3-Etn | 2514.69 | 831.23/1247.28 | 831.22/1247.33 | [M-H2O-3H]3−/[M-H2O-2H]2− |
| [ECA]-Glc3-Gal2-Hep3-Kdo-P3-Etn | 2514.69 | 844.56/1267.32 | 844.55/1267.32 | [M-3H, Na]3−/[M-2H, Na]2− |
| [ECA]-Glc3-Gal2-Hep3-Kdo-GlcN-P2 | 2552.75 | nd/1275.31 | 849.91/1275.37 | [M-3H]3−/[M-2H]2− |
| [ECA]-Glc3-Gal2-Hep3-Kdo-P4-Etn | 2594.65 | 863.88/1296.32 | 863.88/1296.32 | [M-3H]3−/[M-2H]2− |
| [ECA]2-Glc3-Gal2-Hep3-Kdo-P2 | 2998.90 | 998.63/1498.40 | 998.63/1498.44 | [M-3H]3−/[M-2H]2− |
| [ECA]2-Glc3-Gal2-Hep3-Kdo-P3-Etn | 3121.91 | 1039.59/nd | 1039.63/1559.95 | [M-3H]3−/[M-2H]2− |
| [ECA]-Glc3-Gal2-Hep3-Kdo-P3-Etn | 2514.69 | 839.25/1258.34 * | 839.24/1258.35 | [M+3H]3+/[M+2H]2+ |
| [ECA]-Glc3-Gal2-Hep3-Kdo-P3-Etn | 2514.69 | 833.25/nd | 833.23/1249.34 | [M-H2O+3H]3+/[M-H2O+2H]2+ |
| [ECA]-Glc3-Gal2-Hep3-Kdo-P3-Etn | 2514.69 | 846.57/1269.34 * | 846.56/1269.34 | [M+3H, Na]3+/[M+2H, Na]2+ |
| [ECA]-Glc3-Gal2-Hep3-Kdo-GlcN-P2 | 2552.75 | 851.92/1277.31 * | 851.92/1277.38 | [M+3H]3+/[M+2H]2+ |
| [ECA]-Glc3-Gal2-Hep3-Kdo-GlcN-P2-Etn | 2617.76 | 873.56/nd | 873.59/1309.89 | [M+3H, Na]3+/[M+2H, Na]2+ |
| [ECA]-Glc3-Gal2-Hep3-Kdo-P4-Etn | 2594.65 | 865.90/1298.32 * | 865.89/1298.33 | [M+3H]3+/[M+2H]2+ |
ESI-IT, electrospray ionization-ion trap; LOS, lipoligosaccharide; [ECA], trisaccharide biological repeating unit of linear enterobacterial common antigen (ECA): →3)-α-d-Fucp4NAc-(1→4)-β-d-ManpNAcA-(1→4)-α-d-GlcpNAc-(1→, where →4)-β-d-GlcpNAc-(1→ is present in the first repeating unit substituting core oligosaccharide (OS); Glc, glucose; Gal, galactose; Hep, heptose; Kdo, 3-deoxy-d-manno-octulosonic acid; GlcN, glucosamine; P, phosphate group; Etn, ethanolamine. nd, non-detected; * the MS region of double-charged ions is not shown in Figure 2d,e.