Theoretical Quantum-Chemical Simulation of the Structure and Properties of Carnosine Dipeptide by the DFT Method

Abstract

The spatial and electronic structure of the natural carnosine dipeptide in the N3H tautomeric form of its imidazole ring in gas and water environment was studied by the quantum-chemical method in the framework of the electron density functional theory (DFT) with the three-parameter B3LYP hybrid functional. The sufficiently reliable and time-saving extended basis set, taking into account the polarization and diffuse functions 6-31+G (d, p) was used for calculations. All calculations were carried our using the Gaussian 09 software package. GaussView 6.0.16 was used to visualize the obtained results. Geometrical parameters, values of electronic energy, energies of HOMO and LUMO orbitals and the energy gap between them, reactivity descriptors, values of dipole moments, partial charges on atoms, and theoretical IR spectra for gaseous and aqueous media are obtained. Calculations show that the proposed model of the molecule forms a stable structure. The resulting structure is stabilized due to non-covalent interactions in the dipeptide. Molecular electrostatic potential maps (MEP) are constructed to identify potential binding sites. To study the charge transfer and intramolecular interactions that determine the stability of the molecule, an analysis of natural bond orbitals (NBOs) was carried out. Structural rearrangements and changes in various parameters depending on the dielectric constant of the medium are analyzed.