Table 1.
MSE data for 1,4-NQ-modified peptides in human PTEN.
| position | assignment | calculated mass (Da) | observed mass (Da) | analyte modifier |
|---|---|---|---|---|
| 61–74 | a2 | 249.16 | 249.17 | +1,4-NQ C (1) |
| y3 | 375.20 | 375.21 | ||
| y4* | 634.23 | 634.24 | ||
| y5* | 747.31 | 747.33 | +1,4-NQ C (1) | |
| y6* | 1137.5 | 1137.53 | +1,4-NQ C (1) | |
| 81–84 | y2* | 434.15 | 434.16 | +1,4-NQ C (1) |
| y3* | 548.20 | 548.20 | +1,4-NQ C (1) | |
| y2-NH3* | 417.12 | 417.12 | +1,4-NQ C (1) | |
| y3-NH3* | 531.17 | 531.18 | +1,4-NQ C (1) | |
| y4 * | 695.26 | 695.28 | +1,4-NQ C (1) |
Recombinant GST-tagged human PTEN (1.7 μg) was incubated with 1,4-NQ (10 μM) at 25 °C for 30 min in 50 mM Tris-HCl (pH 7.5). After the reaction, the GST-PTEN protein was digested by trypsin and analyzed by nanoUPLC-MSE. The mass number 156.02 was used to calculate 1,4-NQ modification.