THE FLUORESCENCE OF TRYPTOPHYL PEPTIDES

Abstract— Tryptophan lifetimes and relative quantum yields have been determined for a group of small (1–4 residues) peptides and peptide hormones luteinizing releasing factor. mellitin, glucagon. glucagon 22–29, glucagon 1–26. glucagon 1–27 (homoserine)]. All of the larger peptides and most of the smaller peptide anions exhibit nonexponential decay. Peptide quenching in the small peptides is more effective when the bonding is at the amino rather than at the carboxyl end of tryptophan. With the exception of tryptophylglycine. quenching by NH⁺₃ is thought not to involve proton transfer. The results suggest that a decay component of 3–4 ns is expected whenever large peptides and proteins contain a solvent exposed tryptophan.