Theoretical binding affinities and spectra of complexes formed by a cyclic β-peptoid with amino acids

Abstract

AbstractBinding affinities of a cyclic β-peptoid to amino acids were studied using the density functional theory (DFT) at the B3LYP/6-311G(d,p) level after the basis set superior error (BSSE). The host molecule possesses binding ability to amino acids since the binding energies of the complexes formed are negative. The complexes were stabilized via hydrogen bonds between the host and the guest molecules. Based on the B3LYP/6-31G(d) optimized geometries, electronic spectra of the complexes were calculated using the INDO/CIS method. 13C NMR spectra and nucleus-independent chemical shift (NICS) values of the complexes were computed at the B3LYP/6-31G(d) level. Carbon atoms in the carboxyl groups of the complexes are shifted downfield relative to those of the host. Some complexes exhibit aromaticity although the host shows anti-aromaticity. Formation of hydrogen bonds leads to cyclic current formation in these complexes.