When you use the Monoisotopic Precursor Selection (MIPS) filter, the MS selects only the ion clusters with an identifiable monoisotopic peak for data-dependent scans. The MS writes the monoisotopic mass to the raw data file, even though that mass is the most abundant isotope that the data-dependent scan is performed on. The monoisotopic mass and the most abundant isotope can be the same (in the case of most single-charged ions) or different (in the case of most peptides).
NOTE
The following table describes the parameters in the MIPS properties pane.
Parameter | Description |
|---|---|
Monoisotopic Peak Determination | Using the MIPS filter restricts data-dependent scans to those where the monoisotopic precursor can be determined. The monoisotopic peak m/z is written to the raw file while the isolation is centered around the most abundant peak or the monoisotopic peak in the isotopic cluster, depending on the Isolation Window Center setting. MIPS will only function for precursors with resolved isotopes and defined charge states. When using MIPS in combination with Dynamic Exclusion, all isotopes are added to the exclusion list once a single isotope is selected for the data-dependent analysis. Uses a heuristic algorithm, referred to as the "non-standard" monoisotopic assignment algorithm. |
Isolation Window Center | The monoisotopic peak m/z is written to the raw file while the isolation is centered around the most abundant peak or the monoisotopic peak in the isotopic cluster. Select one of the two options:
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