ABSTRACT
A hybrid mass spectrometer composed of a high resolution double focusing instrument (electrostatic analyzer-magnetic sector, EB) and an ion trap analyzer (T) exhibits high sensitivity performance for peptide sequencing with electrospray ionization (ESI). MS2 and MS3 experiments for multiply charged tryptic peptides and larger peptides (e.g., melittin, 2.8 kDa) generate sequence-informative product ions. Collisionally activated dissociation (CAD) of selected precursor ions can also be performed in the interface between the double focusing analyzer and the ion trap (transfer octapole region) to generate product ions. With a low-flow micro-ESI source, which can deliver analyte solution to the source at a flowrate of 10-200 nL/min, tandem mass spectra can be obtained from sub-fmol amounts of melittin. The high resolving power of the MS-I stage combined with the efficiency of the ion trap stage allows for high resolution precursor ion selection with subsequent highly sensitive tandem mass spectrometry (MS/MS) analysis.
Subject(s)
Peptides/analysis , Sequence Analysis/methods , Acyl Carrier Protein/analysis , Amino Acid Sequence , Enkephalin, Methionine/analysis , Hydrolysis , Mass Spectrometry , Melitten/analysis , Molecular Sequence Data , TrypsinABSTRACT
In three application examples we demonstrate how the capabilities of a modern atmospheric pressure ionization (API) source, as a universal LC-MS coupling tool, are supplemented by the high mass resolution available on double focusing sector instruments. The examples include charge state determination in complex electrospray ionization-collisional induced dissociation (ESI-CID) spectra of multiply charged ions, mixture analysis of multicomponent samples without prior chromatographic separation, and very sensitive and highly specific detection of pesticides using atmospheric pressure chemical ionization (APCI).
