Magnetic sector-ion trap mass spectrometry with electrospray ionization for high sensitivity peptide sequencing.

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.