In Vitro: It is found that Autocamtide-2-related inhibitory peptide (TFA) is a potent inhibitor of CaM-kinase II with an IC50 of 40 nM, which is active in the presence or absence of Ca2+/calmodulin. It is 50 and 500 times more potent than CaMK-(281-302Ala286) and KN-93, respectively, under the assay condition used.