TABLE 2.
Accurate masses of the glycan oxonium and glycan-related fragment ions and most plausible empirical formulaa
| Carbohydrate fragment ion | Strain | Mean accurate m/z ± SD | Residue mass (Da) | Elemental composition | Predicted oxonium ion (m/z) |
|---|---|---|---|---|---|
| 399.1 | 630 | 399.1164 ± 0.0012 | 398.1086 | C13H24N2O10P | 399.1163 |
| 284.1 | 630 | 284.0536 ± 0.0010 | 284.0458 | C8H15NPO8 | 284.0530 |
| 214.1 | 630 | 214.0481 ± 0.0072 | 213.0403 | C5H13NO6P | 214.0475 |
| 204.1 | 630 | 204.0865 ± 0.0004 | 203.0787 | C8H14NO5 | 204.0867 |
| 186.1 | 630 | 186.0766 ± 0.0007 | 185.0688 | C8H12NO4 | 186.0761 |
| 116.1 | 630 | 116.0706 ± 0.0003 | 115.0628 | C5H10NO2 | 116.0706 |
| 524.2 | BI-1 | 524.2311 ± 0.0049 | 523.2231 | C22H38NO13 | 524.2338 |
| 204.1 | BI-1 | 204.0864 ± 0.0059 | 203.0745 | C8H14NO5 | 204.0866 |
| 161.1 | BI-1 | 161.0811 ± 0.0072 | 160.079 | C7H13O4 | 161.0808 |
a
For C. difficile strain 630, fragment ions y3 (m/z 389.2513), y2 (m/z 288.2036), and y8 (m/z 836.4114) from the peptide T135-144LLDGTSSTIR were used as references. Hydrogen mass, 1.0078 Da. For C. difficile strain BI-1, fragment ions y3 (m/z 417.2462), y2 (m/z 288.2036), and y8 (m/z 807.335) from the peptide T135-144LLDGSSTEIR glycopeptide ion 807.42+ were used.