 Tamapin has been isolated via detection of the apamin-competing fraction of the venom from the scorpion via a Sephadex G-50 size exclusion chromatography, followed by high performance liquid chromatography (HPLC).An isoform of tamapin, tamapin-2, has been found, in which the tyrosine is replaced by a histadine.Tamapin-2 can also compete very effectively with apamin for binding to synaptosomes.