Botulinum neurotoxins sub-typed

US scientists have succeeded in sub-typing all seven Botulinum neurotoxin serotypes using a novel proteomics approach that combines multi-enzymatic digestion with mass spectrometry. A collaboration between research groups from the CDC and the FDA amended the conventional protocol that uses a single enzyme to digest the protein, because it is does not provide sufficient peptides to give good sequence coverage and unambiguous sub-type assignment.

In its place, they instigated sequential enzyme digestion, with mass spectrometric analysis after each step, as described in Analytical Chemistry. This procedure produced peptides with complementary coverage across the protein so that almost complete sequence coverage was achieved for all of the sub-types. In a test with infected orange juice, 98.4% coverage of a neurotoxin was obtained for unequivocal sub-type identification.