Fluorescent and photo-affinity enkephalin derivatives: Preparation and interaction with opiate receptors

Abstract

The fluorescent and photo-affinity derivatives of enkephalin, Tyr-D-Ala-Gly-Phe-Leu-Lys-N ε-Rhodamine (II) and Tyr-D-Ala-Gly-Phe-Leu-Lys-N ε-nitro-azidophenyl (III), were prepared by conventional methods followed by chemical modification. The two peptides inhibit the binding of 125I-labeled enkephalin to brain membrane preparations, with apparent IC 50 values of 5.9 nM and 5.5 nM for peptides II and III, respectively. The iodinated derivative of peptide III binds specifically to brain membrane preparations with an apparent K d of about 2.1 × 10 −9M.