Since 1978, List Labs products are unsurpassed in quality, consistency, and reliability for the success of your research and development projects! Clostridium botulinum neurotoxins causes botulism in man and animals. Seven immunologically distinct serotypes of neurotoxin, designated types A through G, have been identified. Each is synthesized as a single polypeptide chain (MW 150,000), the holotoxin. When botulinum neurotoxin is exposed to proteases specific peptide bonds are cleaved or “nicked” resulting in the formation of a dichain molecule. Dichain neurotoxin is composed of a light chain region (MW 50,000) linked by a single disulfide bond and non-covalent interactions to a heavy chain (MW 100,000). The light chains are non-toxic proteins that retain the enzymatic activity encoded by the holotoxin. The Type B light chain cleaves the eukaryotic substrate synaptobrevin-2 and VAMPtide fluorogenic peptide substrates offered from List Labs.