Table I. Ion characteristics of isobaric labeling methods.
| Property | iTRAQ4 | iTRAQ8 |
|---|---|---|
| aRep+ | 114–117 | 113–119,121 |
| bLabel+ | 145 | 305 |
| Isobaric ion mass | 144 | 304 |
| Minimum B ion | 202 | 362 |
| Minimum Y ion | 175 | 175 |
| Low mass b/y free window | 0∼175 | 0∼175 |
| Maximum B ion | MH+-174 | MH+-174 |
| Maximum Y ion | MH+-201 | MH+-361 |
| High mass b/y free window | MH+-174∼INF | MH+-174∼INF |
| cPrecursor-Label+ | MH+-144 | MH+-304 |
a Rep+: reporter ions.
b Label+: isobaric tag ion.
c Precursor-Label+: the precursor ion without the isobaric tag.