Charge reduction lowers mass resolving power for isotopically resolved electrospray ionization Fourier transform ion cyclotron resonance mass spectra

Electrospray ionization of synthetic or biological macromolecules above sim ilar to1-2 kDa in mass typically produces ions of multiple charge states. S everal recent papers have illustrated charge reduction as a means to simpli fy low-resolution electrospray ionization mass spectra, at the cost of sign ificant loss in signal-to-noise ratio. However, if mass resolving power is sufficiently high las in Fourier transform ion cyclotron resonance mass spe ctrometry) to resolve the heavy-atom isotopic distribution, then charge red uction actually lowers mass resolving power by a factor proportional to the ion charge. For proteins or nucleic acids of 10-50 kDa in mass, reducing t he charge state to unity thus lowers mass resolving power by a factor of 10 -50. In other words, as long as it is possible to resolve the isotopic dist ributions, charge reduction has no advantages for electrospray ionization m ass spectrometry and has the very serious disadvantage of greatly degraded mass resolving power. Copyright (C) 2001 John Wiley & Sons, Ltd.