Fourier-transform electrospray instrumentation for tandem high-resolution mass spectrometry of large molecules

Department of Chemistry, Baker Laboratory, Cornell University, Ithaca, New York, USA Mass spectrometry instrumentation providing unit resolution and lo-ppm mass accuracy for molecules larger than 10 kDa was first reported in 1991. This instrumentation has now been improved with a 6.2-T magnet replacing that of 2.8 T, a more efficient vacuum system, ion injection with controlled ion kinetic energies, accumulated ion trapping with an open-cylindrical ion cell, acquisition of 2M data points, and updated electrospray apparatus. The resulting capabilities include resolving power of 5 × 105 for a 29-kDa protein, less than l-ppm mass measuring error, and dissociation of protein molecular ions to produce dozens of fragment ions whose exact masses can be identified from their mass-to-charge ratio values and isotopic peak spacing.