Ac-Arg-Phe-Met-Trp-Met-Arg-NH2

Acetalin-3 (Ac-RFMWMT-NH2), a hexapeptide, is a μ opioid receptor antagonist with high affinity for μ and κ3 opioid receptor, weak affinity for κ1 receptors and no affinity for κ2 receptors[1].

μ Opioid Receptor/MOR

[1] C T Dooley, et al. Acetalins: opioid receptor antagonists determined through the use of synthetic peptide combinatorial libraries. Proc Natl Acad Sci U S A. 1993 Nov 15;90(22):10811-5. DOI:10.1073/pnas.90.22.10811