Chemistry & stability

A simple peptide with a serious durability problem

DSIP’s chemistry is almost disappointingly plain: a short, linear chain of nine amino acids with no exotic features. Yet that very simplicity creates its biggest obstacle. The peptide is broken down rapidly in blood and tissue, and the antibody assays used to track it count more than the intact peptide: by early estimates, only a small part of the total immunoreactivity is probably the free nonapeptide.

This unit covers the sequence, why it degrades so fast, the analog programs built to fix that, and the measurement problem that haunts the entire literature.