[Ala1,3,11,15]-Endothelin (53-63) (TFA) is an ET B agonist. [Ala1,3,11,15]-Endothelin (53-63) (TFA) has selectivity for ET B with IC 50 values range from 0.33 nM to 0.61 nM. [Ala1,3,11,15]-Endothelin (53-63) (TFA) can be used for the research of vasoconstriction.