CTAP (trifluoroacetate salt) from Cayman Chemical

A water soluble, cyclic octapeptide which acts as a receptor antagonist that is selective for the µ opioid receptor (IC50 = 3.5 nM) over the δ receptor (IC50 = 4,500 nM); a poor antagonist of the somatostatin receptor (IC50 = 14.3 µM)