DOPA’s reactivity leads to multiple chemical pathways relevant to wet tissue adhesion. DOPA’s side chain, catechol (1), forms the highly reactive o-quinone (2) intermediate upon (auto)oxidation with dissolved oxygen, a strong oxidant (e.g. NaIO4) or basic conditions. o-Quinone can then react with tissue pendent lysine or cysteine residues toform covalent interfacial bonds via Michael-type addition (3, 4) or Schiff base formation (5). Alternatively, tanning ofo-quinone also results in polyphenol crosslinks (6), which contribute to the elastic properties of the byssus or synthetic wet adhesives.