Probing gold cluster- Purine nucleobase interactions in aqueous environment: Insights from quantum mechanics and molecular simulation.

This study explored the binding interactions between gold clusters Au, where n = 1-20 and DNA nucleobases, specifically adenine and guanine, aiming to uncover opportunities for use in biosensors, targeted drug transport, and similar biomedical areas. The Au-DNA base complexes were optimized by density functional theory using the B3LYP functional in combination with LANL2DZ for gold atoms and 31++G(d,p) for non-metal elements and then comprehensive supplementary calculations using PBE-D3/cc-pVTZ functional. Then their electronic binding energies were analyzed in both gas and aqueous phases. Subsequent Monte Carlo simulation techniques were employed to evaluate the solvation and binding free energies of these Au-DNA base complexes in aqueous environments. Quantum mechanical calculations elucidated potential interactions between Au clusters and DNA bases in both gaseous and aqueous environments. Analysis revealed that Au-guanine and Au-adenine complexes demonstrated superior structural stability, exhibiting enhanced binding energies in both phases. Frontier orbital analysis revealed that Au complexes exhibit reduced chemical reactivity, making them ideal candidates for precisely defined nanostructures in therapeutic and drug delivery systems. In contrast, Au clusters displayed elevated reactivity profiles, suggesting their potential applicability in radical-mediated processes. Monte Carlo simulations in aqueous solution suggested that Au clusters (n ≥ 2) effectively interact with both purine DNA bases. Additionally, the solvation free energy calculations demonstrated enhanced solubility of Au clusters upon binding to purine bases, a favorable property for biological applications. This investigation highlights the substantial promise of gold-purine hybrid clusters for biomedical implementation, attributable to their optimized aqueous solubility and precisely modulable electronic characteristics.