bungarotoxin

noun

bun·​ga·​ro·​tox·​in ˈbəŋ-gə-rō-ˌtäk-sən 

: a potent polypeptide neurotoxin that is obtained from krait venom and yields three electrophoretic fractions of which the one designated α is used especially to label acetylcholine receptors at neuromuscular junctions because it binds irreversibly to them and blocks their activity

—often used with one of the Greek prefixes α-, β-, or γ- to indicate the electrophoretic fractions