Fig. 6.

Dynamic programming to identify triply modified peptide, A+42ALFC+48LESAW+16K, and its MS/MS spectrum. First, two sequence tags, ALF (t₁) and LESA (t₂), were derived from the spectrum. The t₀ and t₃ tags are special tags of length zero that define the start and end nodes of dynamic programming. Numeric figures at both ends of a tag represent mass differences (Δ mass) between the tag's flanking mass and the mass of subsequence corresponding to the flanking mass region: the left figure for N terminus and the right figure for C terminus. They represent the total modified mass of the region. To restrict jumps between nodes, nodes are labeled according to the position of matched tag: 0 for before the tag, 1 for inside the tag, and 2 for after the tag. Dashed arrows represent all possible jumps satisfying constraints on the sequence tags and the highlighted path represents the optimal alignment. For a modification jump, its modified mass is defined as a difference between N-terminal Δ mass values of two tags.