Kinase experiment:

Membrane protein (40 μg) is incubated in 0.5 mL volume of 50 mM Tris, 0.2 mM EGTA, 1 mM MgCl2, 100 mM NaCl, 0.1% BSA, 0.15 mM bacitracin; pH 7.4, GDP (33 μM), and ~150 pM GTPγ[35S]. Varying concentrations of reference ligands (Dermorphin, N/OFQ, Dynorphin-A and Leu-enkephalin) or DeNo (1 pM-10 μM) is added prior to incubation. Non-specific binding is determined in the presence of unlabeled GTPγS (10 μM). Samples are incubated at 30℃ for 1 h with gentle agitation. Reactions are terminated by vacuum filtration through dry Whatman GF/B filters, using a Brandel harvester[2].

Dermorphin is a natural heptapeptide μ-opioid receptor (MOR) agonist found in amphibian skin.

Dermorphin, a peptide isolated from the skin of Phyllomedusa frogs and the peptide receptor (NOP) component by the endogenous agonist nociceptin/orphanin FQ (N/OFQ). In displacement binding studies at CHOhMu, Dermorphin and DeNo displac the binding of [3H]-DPN in a concentration dependent and saturable manner. Dermorphin displays an affinity of 7.17, while N/OFQ fails to displace [3H]-DPN at the Delta receptor. Dermorphin and DeNo stimulate the binding of GTPγ[35S] in a concentration dependent and saturable manner at the Mu receptor[2].

[1]. Tiwari V, et al. Activation of Peripheral μ-opioid Receptors by Dermorphin [D-Arg2, Lys4] (1-4) Amide Leads to Modality-preferred Inhibition of Neuropathic Pain. Anesthesiology. 2016 Mar;124(3):706-20. [2]. Bird MF, et al. Characterisation of the Novel Mixed Mu-NOP Peptide Ligand Dermorphin-N/OFQ (DeNo). PLoS One. 2016 Jun 7;11(6):e0156897.