DFT Investigation of Guanosine-Arginine Interaction: NCI-RDG, QTAIM, ELF, NBO and Docking Analysis

This study aims to cast light on the physico-chemical properties of the interaction between guanosine and arginine (Guan-Arg) using DFT/M062x/6-311G(d,p) level of theory in vacuum, water, ethanol and in dimethylsulfoxide (DMSO). This interaction occurs through two hydrogen bonds, HB1 (N•••H-O) and HB2 (NH•••O), in addition to (CH•••O) interaction. NBO and QTAIM indicate the electrostatic character of hydrogen bonds and (CH•••O) interaction. Energetically, HB1 (E2 = 42.92 kcal/mol) should be more stable than HB2 (E2=23.01 kcal/mol) in vacuum. With solvents, the hydrogen bond is more stable in ethanol (HB1: E2= 39.93 kcal/mol and HB2: E2 =13.90 kcal/mol). QTAIM shows the bond critical points (BCPS) and ring critical points (RCPS) at the interaction region of Guan-Arg having low values of electronic density ρ(r) with positive Laplacian of electronic density 𝛻2ρ(r), confirming the electrostatic character of the hydrogen bonds and (CH•••O) interaction. ELF and NCI-RDG analyses were performed and discussed, and they confirm the QTAIM results. Analysis of partial charges indicates that the electronic charge density transfer (ECDT) should occur through hydrogen bonds in vacuum and in different solvents, which is characterized through NBO analysis by the reversible transfer of electronic charge density (RTECD) between guanosine and arginine orbitals. Dipole moment and polarizability increase linearly with the dielectric constant (ɛ) of the medium.