QUADRUPOLAR AXIALIZATION FOR IMPROVED CONTROL OF ELECTROSPRAYED PROTEINS IN FTICR MASS-SPECTROMETRY

Quadrupolar axialization is implemented on a high-held electrospray io nization Fourier transform ion cyclotron resonance mass spectrometer, The method is utilized to perform highly efficient remeasurement of sm all proteins which were not previously amenable to the remeasurement p rocess. For example, 100 consecutive remeasurements of the same popula tion of melittin ions (MW 2845) yield the theoretical 10-fold improvem ent in signal-to-noise ratio compared to the first measurement. The ef ficiency of the cooling process is evaluated as a function of excitati on radius and ion mass, and the results are compared to instrumental p erformance prior to the implementation of quadrupolar axialization. Th e maximum achievable excitation radius for efficient remeasurement is increased from 18% to 52% of the trapped ion cell radius. The applicat ion of quadrupolar axialization during the electrospray ion accumulati on event results in a factor of 3 improvement in sensitivity when acqu iring bovine insulin (MW 5734) spectra under high-resolution condition s. The mass selectivity of the technique is used to isolate a single c harge state of horse myoglobin (MW 16 951).