Separation of protein conformers using electrospray-high field asymmetric waveform ion mobility spectrometry-mass spectrometry

High-field asymmetric waveform ion mobility spectrometry (FAIMS) is a technique for continuous gas-phase ion separation at atmospheric pressure (760 Torr) and room temperature. FAIMS separates ions based on changes in mobility at high electric fields. Ion focusing in a cylindrical geometry FAIMS provides high ion transmission efficiency, thereby making FAIMS an ideal interface for transferring ions from an electrospray ionization (ESI) source to a mass spectrometer (MS). In this study, an ESI-FAIMS-MS instrument was used to study the conformers of the protein bovine ubiquitin. Multiple conformers for some charge states of bovine ubiquitin were resolved by FAIMS, including at least three for the +8 charge state. The number and abundance of the conformers of several charge states of bovine ubiquitin were dependent on solution pH and solvent composition. Mass spectra of individual conformers showed conformer-specific distributions of sodium and phosphate adduct ions. ESI-FAIMS-MS conformational data are compared with literature results that were collected using ESI drift tube mobility spectrometry/mass spectrometry. (C) 2000 Elsevier Science B.V.