Practice question

In electrospray ionization of a single purified protein, multiple protonation states coexist because different numbers of basic residues can be protonated during droplet evaporation process. Each charge state appears as distinct peak with its own m/z value, creating an envelope of closely spaced signals rather than one peak. Mathematical deconvolution transforms this envelope to zero-charge molecular weight. Aggregation, oxidation, or denaturation would produce additional heterogeneity or broaden peaks, but characteristic ladder of peaks for pure protein arises specifically from multiple charging phenomenon intrinsic to ESI mechanism in protein analysis.