ULTRAHIGH MASS ACCURACY IN ISOTOPE-SELECTIVE COLLISION-INDUCED DISSOCIATION USING CORRELATED SWEEP EXCITATION AND SUSTAINED OFF-RESONANCE IRRADIATION - A FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE MASS-SPECTROMETRY CASE-STUDY ON THE [M+2H](2+) ION OF BRADYKININ

Using electrospray ionization with a 9.4 T Fourier transform mass spec trometer, fragment ion spectra were acquired for a single isotopomer o f doubly protonated bradykinin (molecular mass, 1059.6 Da). Correlated sweep excitation methods were applied to mass-select the single isoto pomer (m/z = 530.8), Sustained off-resonance irradiation was used to a ctivate and fragment the ions. The accuracy (in terms of m/z) in detec tion of the fragment ions was on average 1.2 ppm, making the assignmen ts unambiguous. The methods employed would be generally applicable to ions in the mass range of approximately 50 Da to 50 kDa.