1H NMR relaxation investigation of acetylcholinesterase inhibitors from huperzine A and derivative

The binding properties of huperzine A (1) with Torpediniforms Nacline acetylcholinesterase (TnAChE) were investigated by 1H NMR methods. The noselective, selective and double-selective spin-lattice relaxation rates were acquired in absent and present of TnAChE at a ratio [ligand]/[protein]=1:0.005. The selective relaxation rates shown protons of 1 had dipole–dipole interaction with protein active site protons. The motional correlation time of bound ligand was calculated by double-selective relaxation rate at 1 τ2,3=40.5 ns at 298 K, which showed 1 had high affinity with TnAChE. The experiments give a possible method to use TnAChE to locate the new huperzine A derivatives as AChE inhibitors.