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Abstract: A theoretical study of aryl succinic and maleic acid derivatives, which are potent inhibitors on bovine acetylcholinesterase activity, was done by means of using a B3LYP/6-31G(d,p) level. Therefore, the Atoms in Molecules theory was employed to calculate the properties of the critical point such as density, Laplacians, and ellipticities. Furthermore, reactivity descriptors such as local softness were calculated in order to predict the reactive sites in the molecule. These results were corroborated by Laplacian values. The electrophilic attack (high sk-/sk+ value) occurs in the O7′ atom for 1, 2, 4, 6, 7, 8 and 9 as well as in the nitrogen atom for 3 and 5. All ligands are susceptible to nucleophilic attacks in the carbonyl carbon, whether such carbon be ester, amide or imide. In accordance with the theoretical calculations, the lowest electron density is located in these regions. Furthermore, the heteroatoms are susceptible to suffering elecrophilic attack, which leads to the conclusion that the ligand-enzyme recognition is by retro-electron donation. This is confirmed by the energies of the HOMO of the aromatic ring as well as the LUMO of the lateral chains. [Copyright &y& Elsevier]

Values of relative interaction energy between an isobutane molecule and the surface of the H-mordenite zeolite were obtained. Sixteen tetrahedral sites were taken into account for the surface. Results showed that the adsorption energies were 4 and 8 kJ/mol, for ab initio restricted Hartree–Fock (RHF) method and density functional Becke–Lee–Yang Parr (B3-LYP) approaches, respectively, when C2&z.sbnd;H2 bond is located in front of H+ atom of H-mordenite surface. The minimum value for the interaction in the adsorption was around 2.25 and 2.50 A˚ distance from the DFT and ab initio method, respectively. The interaction of isobutane by methyl groups side over the catalytic surface caused a repulsive interaction. Therefore, adsorption of isobutane is a selective process by the H2 side of the molecule. Calculations were done by employing the 6-31G** basis set. [Copyright &y& Elsevier]

Highlights: [•] Quantum chemistry properties of ChEs inhibtors. [•] QSAR studies of ChEs inhibitors. [•] Configuration possibilities of AChE inhibitors. [•] Conformation changes of ChEs. [ABSTRACT FROM AUTHOR]