Biomolecular Adsorption at Aqueous Silver Interfaces: First-Principles Calculations, Polarizable Force-Field Simulations, and Comparisons with Gold

Abstract

The molecular simulation of biomolecules adsorbed at noble metal interfaces can assist in the development of bionanotechnology applications. In line with advances in polarizable force fields for adsorption at aqueous gold interfaces, there is scope for developing a similar force field for silver. One way to accomplish this is via the generation of in vacuo adsorption energies calculated using first-principles approaches for a wide range of different but biologically relevant small molecules, including water. Here, we present such first-principles data for a comprehensive range of bio-organic molecules obtained from plane-wave density functional theory calculations using the vdW-DF functional. As reported previously for the gold force field, GolP-CHARMM (Wright, L. B.; Rodger, P. M.; Corni, S.; Walsh, T. R. GolP-CHARMM: first-principles based force-fields for the interaction of proteins with Au(111) and Au(100). J. Chem. Theory Comput. 2013, 9, 1616-1630), we have used these data to construct a a new force field, AgP-CHARMM, suitable for the simulation of biomolecules at the aqueous Ag(111) and Ag(100) interfaces. This force field is derived to be consistent with GolP-CHARMM such that adsorption on Ag and Au can be compared on an equal footing. Our force fields are used to evaluate the water overlayer stability on both silver and gold, finding good agreement with known behaviors. We also calculate and compare the structuring (spatial and orientational) of liquid water adsorbed at both silver and gold. Finally, we report the adsorption free energy of a range of amino acids at both the Au(111) and Ag(111) aqueous interfaces, calculated using metadynamics. Stronger adsorption on gold was noted in most cases, with the exception being the carboxylate group present in aspartic acid. Our findings also indicate differences in the binding free energy profile between silver and gold for some amino acids, notably for His and Arg. Our analysis suggests that the relatively stronger structuring of the first water layer on silver, relative to gold, could give rise to these differences.

Non-covalent adsorption of amino acid analogues on noble-metal nanoparticles: influence of edges and vertices

“…The interfacial structuring of liquid water at inorganic material interfaces is thought to exert substantive influence of adsorption behaviour of biomolecules at such surfaces. This has been reported not only in the cases of strongly hydrophilic interfaces such as titania and silica 78,79 but also for noble metals, [28][29][30]34,[36][37][38] including very recent elucidation of the role of interfacial water in facetselective peptide adsorption at different aqueous Au planes. 34 On the basis of these previous studies, we predict that the differences in binding-site preferences noted here will confer a highly nonuniform spatial distribution of interfacial solvent structuring around the NMNP.…”

“…Please do not adjust margins Please do not adjust margins To identify equilibrium adsorption geometries and subsequently calculate adsorption their corresponding adsorption energies on the NM 147 NP (either Au 147 or Pt 147 ), we followed the process reported previously to calculate the adsorption energy of small molecules on infinite planar metal surfaces. [36][37][38] Initially, each molecule was positioned close to the NP surface and the geometry was optimised with all atoms in both the adsorbate and the NP allowed to relax. We explored a wide range of adsorbate/surface configurations in each case.…”

“…36,38 For all adsorbates these data are summarised graphically in Fig. 5b), with absolute values provided in Table S7 in the ESI.…”

Two-Photon Absorption of Metal-Assisted Chromophores

“…In general, the NATSB molecules show a greater affinity to the Au(111) surface over the Ag(111) surface, in accordance with the literature reports that gold is mostly favored over silver for adsorption of amino acids. 19 The different adsorption geometries lead to different behavior in the lateral rotation of the NATSB molecule. Figure 2 shows time-evolution of the angle between the NO 2 → NH 2 vector of NATSB and the x-axis, which describes the rotation of the molecule around the normal direction of the metal surface, i.e.…”

Force fields for simulating the interaction of surfaces with biological molecules

“…The GolP-CHARMM FF [43] mentioned previously incorporates polarization in a gold surface using a rotating rod model, retaining the fixed-charge description in the aqueous phase. Walsh and co-workers have also recently applied this method to silver [34] and graphite [39] surfaces, where they take advantage of the computational efficiency afforded by the fixed-charge treatment of the aqueous phase to calculate amino acid binding free energies.…”