Capillary Zone Electrophoresis−Electrospray Ionization-Tandem Mass Spectrometry for Top-Down Characterization of the

ABSTRACT: Capillary zone electrophoresis (CZE) with an electrokinetically pumped sheath-flow nanospray interface was coupled with a high-resolution Q-Exactive mass spectrometer for the analysis of culture filtrates from Mycobacterium marinum. We confidently identified 22 gene products from the wildtype M. marinum secretome in a single CZE−tandem mass spectrometry (MS/MS) run. A total of 58 proteoforms were observed with post-translational modifications including signal peptide remov-al, N-terminal methionine excision, and acetylation. The conductivities of aqueous acetic acid and formic acid solutions were measured from 0.1 % to 100 % concentration (v/v). Acetic acid (70%) provided lower conductivity than 0.25 % formic acid and was evaluated as low ionic-strength and a CZE−MS compatible sample buffer with good protein solubility. Mass spectrometry-based proteomics is an effective toolfor protein identification, characterization, and quanti