Study of CO⋯HN Hydrogen bond interactions in amyloid beta (Aβ): A DFT study of the electric field gradient and CS tensors and NBO analysis

A systematic computational density functional theory (DFT) study was carried out in amyloid-beta (Aβ) structure to investigate the hydrogen bonding interactions (HBs) effects on Chemical shielding (CS) and electric field gradient (EFG) tensors in site of hydrogen, oxygen, nitrogen and carbon nuclei. The results indicate that these tensors are more sensitive to the HB interactions in dimer model than those of trimer model. The calculated 15N and 13C in CS tensors in trimer model are in good agreement with experimental data. Natural bonding orbital analysis, NBO, indicate a reasonable correlation between 14N quadrupole coupling constant (CQ) and strength of Fock matrix elements (Fij). Moreover, the quantum chemical calculations indicated that the intermolecular the HB interactions play an essential role in variation of the relative orientation of CS and EFG tensors of nitrogen, hydrogen and oxygen nuclei in the molecular frame axes. Finally, 17O CQ and ηQ show great dependency to backbone conformation, specifically dihedral angles ψ (psi).