In Silico Study of Metoclopramide as A Small Molecule of Dopamine D2 Receptor: a Quantum-Mechanical (QM) Based Molecular Docking Treatment

The present research exploration will contain studying the molecular structure, bonds nature, stability, reactivity and electronic properties of the title molecule.The molecular optimization and all theoretical computations were carried out by density functional theory (DFT) method using the hybrid B3LYP (Becke, three-parameter, Lee-Yang-Parr) exchange-correlation functional employing the 6-31G(d,p) basis set of theory. Quantum-mechanical (QM) computations of the molecular structure geometry of the molecule under study were calculated with scaled quantum mechanics. The global reactivity descriptors like energy gap (Eg), ionization potential (IP), electron affinity (EA), chemical hardness (η), chemical softness (S), electronegativity (χ), electronic chemical potential (µ) and electrophilicity index (ω) can be obtained from the energies of the frontier molecular orbitals (HOMO and LUMO). The calculated global reactivity indices indicated that metoclopramide which was a stable small molecule can bind with the residues of the dopamine D2 receptor (D2R). Molecular docking studies showed that the steric interactions of the ligand with the residues Phe 198, Phe 382, Ala 122, Thr 119, Ser 197, Trp 386, Phe 390, Val 115, Cys 118 and Asp 114 from the protein binding site are the main binding modes between the ligand and the receptor.