This is a myristoylated form of Autocamtide-3-Derived Inhibitory Peptide (AC3-I), a highly specific inhibitor of Calmodulin-Dependent Protein Kinase ll (CaMKII) that is resistant to proteolysis. AC3-I is derived from Autocamtide-3, a substrate for CaMKII, with the Thr-9 phosphorylation site substituted with Ala.