Protein Mass Determination: ESI-QTOF
Mass spectrometry is an ideal method for protein mass determination. The two primary methods for ionization of proteins are electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI). In ESI ionization proteins are ionized in solution and carry multiple charge state (see figure below which shows a ESI-QTOF scan of myoglobin protein). The advantage of using ESI-QTOF analysis for protein mass determination is that due to the high charge state of proteins their m/z measurements is typically less than 2000 and the TOF detector has a very good resolution and mass accuracy in this scan range. This results in more accurate mass measurements for proteins in ESI-QTOF.
