Figure 4

Observed to theoretical N2 Intensity ratios for all combinations of amino acids in the first and second positions. The 20 × 20 table of the median values of the N2 ratio of observed intensity to theoretical intensity when the amino acid in the second position is preceded by the amino acid in the first position. The table is displayed as a grid of colored rectangles with the colors corresponding to the values in the table. Glycine, leucine, and proline in the second position consistently have higher observed:theoretical ratios which means the peptides with glycine, leucine, or proline in the second position tend to be under-predicted.