What is C-terminal tryptic peptide? A biologist wrote to me: `... C- or N-terminus,... For example, a C-terminal tryptic peptide like AGWRGSDSHSR, would be...` I don't have any idea what that is. When I google the term ("C-terminal tryptic peptide"), nothing obvious came up. What's that? Why `AGWEGSDSHSR` is a "C-terminal tryptic peptide"?

Its quite simple if you look at the basics! Lets have a look at the sequence you give:

> AGWRGSDSHSR

Write that in 3-letter terms1:

> Ala-Gly-Trp-Arg-Gly-Ser-Asp-Ser-His-Ser-Arg

Pay attention to the C-terminus. The last amino acid residue in the sequence is Arginine. Now, its well established that Trypsin cleaves a polypeptide _after_ (i.e. towards the C-terminal side of) Lysine and Arginine2.

Thus, C-terminal tryptic peptide is the peptide that remains after a polypeptide has been treated with Trypsin.