A model of acetylcholinesterase bound to Acetylcholine as a tetrahedral intermediate during the hydrolysis of the neurotransmitter. Original structure from Raves, M.L., Harel, M., Pang, Y.-P., Silman, I., Kozikowski, A.P., Sussman, J.L., “Structure of acetylcholinesterase complexed with the nootropic alkaloid, (-)-huperzine A.” (1997) Nat.Struct.Mol.Biol. (4), pp. 57-63. Structure obtained from the RSCB Protein Databank ID# 1ACE.