precursor ion

precursor ion

In mass spectrometry, the ion that dissociates to a smaller fragment ion, usually due to collision-induced dissociation in an multistage/mass spectrometry (MS/MS) experiment.
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The system will provide the capability to separately isolate and fragment more than 5 precursor ions for each full-scan profile and will provide the capability to isolate the precursor ion in the range m/z 50-4 000.
The PTR-TOFMS and classic PTR-QMS series can include switchable reagent ions (PTR+SRI-MS), where instead of the single precursor ion ([H.sub.3]+) used in PTR-MS systems, NO+ and [O.sub.2]+ can be used to ionize trace constituents chemically in gas samples.
Precursor ion selection allows ions from complex mixtures or closely associated neighboring isotopic envelopes to be isolated and fragmented easily.
1, A and B, show the isotope distribution for the [(M+2H).sup.2+] precursor ion for the naturally occurring peptide DYVSQFEGSALGK and the [D.sub.3]-leucine-labeled peptide, respectively.
The Analyst software incorporates enhanced stability for instrument control and data acquisition with added functionality for intelligent precursor ion selection in MS/MS.
QuanTIS precursor ion allows specific isolation of precursor ions designated for MS/MS, thus achieving accurate and easy-to-interpret results.
The ion trap is not only used to focus ions before ejection into the TOE but also supports fragmentation, M[S.sup.n] analysis and a high precursor ion selection (resolution >1000 at 1000 m/z).
With triple quadrupoles, SRM has implied that the precursor ion is selected with a mass tolerance of [+ or -]0.5 m/z or higher.
Isotope-labeled peptides; the analytical internal standard (IS) DR[V [sup.13]C, [sup.15]N]YIHPFHL; the degradation standard (DS) DR[V [sup.13]C,[sup.15]N]Y[I[sup.13]C, [sup.15]N]HPFHL; and the DS DRVYIH[P [sup.13]C,[sup.15]N]FHL and DRVYI[H [sup.15]N] PF[H [sup.15]N]L used for precursor ion and targeted selected reaction monitoring (SRM) studies were purchased from Sigma Life Sciences or Cambridge Isotope Laboratories.
If, for example, a precursor ion of a target analyte in a pure solution exhibits an m/z ratio of 582 and gives rise to 2 major fragment ions by MS/MS, these 2 fragments will exhibit a characteristic fragment-intensity ratio (e.g., the fragment with an m/z ratio of 188 is 3 times more intense than a fragment with an m/z ratio of 210, yielding a 3:1 ratio).
For the acquisition of both [MS.sup.2] and [MS.sup.3] spectra, we set the precursor ion isolation width at 2 and the collision energy at 45%.
During each infusion a precursor ion scan from m/z 900 to m/z 990 was performed (30-s integration).