Fig. 6.

LC-MS and RePlay pepsin digestion analysis of protein standard mixture containing carbonic anhydrase, lactoglobulins A and B, cytochrome c, ubiquitin, and myoglobin. a, a total ion chromatogram of the initial intact protein RPLC analysis. b, the corresponding total ion chromatogram for the RePlay pepsin digestion analysis. c, a plot of the normalized number of digested peptides corresponding to a particular protein as a function of elution time. The darker boxes indicate more peptides were observed. Each row contains data corresponding to a different protein. From top to bottom, these proteins are cytochrome c, ubiquitin, lactoglobulin A, lactoglobulin B, myoglobin, and carbonic anhydrase. d and e, mass spectra of both the initial intact RPLC separation plotted in black and the RePlay pepsin digestion analysis plotted in grey. A significant number of intact ubiquitin (d) and myoglobin (e) peaks were only detected in the initial RPLC run, and digestion products were only observed in the RePlay run as illustrated in the zoomed-in regions.