α-Bungarotoxin, a 74-amino acid peptide extracted from Bungarus multicinctus venom, binds with high affinity to the α-subunit of the nicotinic acetylcholine receptor (AChR) of neuromuscular junctions. The biotin-XX α-bungarotoxin can be used in conjunction with labeled streptavidin or avidin to visualize this receptor. Labeled -bungarotoxin conjugates can be used to facilitate identification of nicotinic AChRs and to localize neuromuscular junctions.