ELECTROSPRAY MASS-SPECTROMETRY OF SOME PROTEINS AND THE AQUEOUS-SOLUTION ACID-BASE-EQUILIBRIUM MODEL IN THE NEGATIVE-ION DETECTION MODE

Basic solutions of myoglobin, beta-lactoglobulin, pepsin and ubiquitin have been examined by means of electrospray mass spectrometry in the negative ion detection mode. The distribution of protein ions in the mass spectra was found to correlate well with the distribution of protein species in solution calculated from published titration data. These results lend further credibility to an earlier proposed aqueous solution acid/base equilibrium model, which relates the ''bell-shape'' ion distribution observed in the electrospray mass spectrometry of proteins to the distribution of protein ions in solution.