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