Cn12 isolated from the venom of the scorpionCentruroides noxiushas 67 amino-acid residues, closely packed with four disulfide primary structure and disulfide bridges were is not lethal to mammals and arthropodsin vivoat doses up to 100lgper structure was determined by proton NMR using 850 dis-tance constraints, 36 /angles derived from 36 coupling constants obtained by two different methods, and 22 hydrogen overall structure has a two and half turn a-helix (residues 24–32), three strands of antiparallel b-sheet (residues 2–4, 37–40 and 45–48), and a type II turn (residues 41–44)
