Adsorption Mechanisms of Nucleobases on the Hydrated Au(111) Surface

The
solution environment is of fundamental importance in the adsorption
of molecules on surfaces, a process that is strongly affected by the
capability of the adsorbate to disrupt the hydration layer above the
surface. Here we disclose how the presence of interface water influences
the adsorption mechanism of DNA nucleobases on a gold surface. By
means of metadynamics simulations, we describe the distinctive features
of a complex free-energy landscape for each base, which manifests
activation barriers for the adsorption process. We characterize the
different pathways that allow each nucleobase to overcome the barriers
and be adsorbed on the surface, discussing how they influence the
kinetics of adsorption of single-stranded DNA oligomers with homogeneous
sequences. Our findings offer a rationale as to why experimental data
on the adsorption of single-stranded homo-oligonucleotides do not
straightforwardly follow the thermodynamics affinity rank.