Screenshots from two implementations of the Mason viewer on data-driven web applications. (A) Mason is used to show protein sequence coverage, relative protein abundance, and relative peptide abundance across many conditions. The top viewer compares the data across multiple developmental stages of the model organism C. elegans, and the bottom viewer compares the data across multiple mass fractions. The summary bar to the right of the viewer indicates overall relative protein abundance (as compared between conditions in the respective viewers). The protein and peptide abundance is shown using shades of red, where black represents the least abundance and bright red represents the most. The rows with red boxes to the left of the labels may be expanded to disambiguate the observed peptides. Each disambiguated peptide may be clicked on to view the underlying mass spectrometry data. (B) Mason is used to show protein sequence coverage (viewer with red bars) among many mass spectrometry runs. The bars to the right represent total sequence coverage for the protein in the respective run. Shades of red in the rows indicate the quality of scores the peptide identification received, and the shade of red in the row level summary bar serves as a secondary indication of protein sequence coverage. Each row with the red box to the left of the label may be expanded to disambiguate overlapping peptides, and each peptide may be moused-over to view summary information and clicked on to view underlying mass spectrometry data. The other viewers (purple, green, cyan, and black) show annotations for this protein from other sources.