Improved fourier-transform ion-cyclotron-resonance mass spectrometry of large biomolecules.

Initial results from a Fourier-transform mass spectrometer with a 6.2 Tesla magnet using electrospray ionization show substantial improvements in resolution, mass accuracy, mass range, signal/noise, and tandem mass spectromehy capabilities compared to our earlier 2.8 T instrument that demonstrated the first unit resolution mass spectra of molecules as large as myoglobin (17 kDa). The new instrument exhibits greater than 10(6) and 10(5) resolving power for 8.6 and 29 kDa, respectively, proteins. Using an internal standard, the mass measuring error for myoglobin is less than 1 ppm. Nozzle-skimmer dissociation during electrospray of carbonic anhydrase (29 kDa) has yielded 38 fragment ions for which both mass and charge are identifiable; of these, 21 have been assigned to expected oligopeptide fragments.