[Semiempirical calculations of the structure of apamine].

Conformational properties of the neurotoxin apamine were investigated starting from the known amino acid sequence. Nonvalent and electrostatic interactions, hydrogen bonding and torsional energies were computed by variation of all backbone and side chain dihedral angles. In a search for the spatial structure of the molecule, di-, tri-, tetra- etc. fragments were subsequently analyzed. As the result, the apriori calculations of the 15-residue apamine fragment revealed strong energy differentiations of forms. The lowest energy conformation has a folded backbone, with an orientation of Cys-1--Cys-11 and Cys-3--Cys-15 side chain pairs favoring the formation of disulfide bridges.