Aqueous Peptide–TiO₂ Interfaces: Isoenergetic Binding via Either Entropically or Enthalpically Driven Mechanisms

Abstract

A major barrier to the systematic improvement of biomimetic peptide-mediated strategies for the controlled growth of inorganic nanomaterials in environmentally benign conditions lies in the lack of clear conceptual connections between the sequence of the peptide and its surface binding affinity, with binding being facilitated by non-covalent interactions. Peptide conformation, both in the adsorbed and non-adsorbed state, is the key relationship that connects peptide-materials binding with peptide sequence. Here, we combine experimental peptide-titania binding characterization with state-of-the-art conformational sampling via molecular simulations to elucidate these structure/binding relationships for two very different titania-binding peptide sequences. The two sequences (Ti-1: QPYLFATDSLIK and Ti-2:GHTHYHAVRTQT) differ in their overall hydropathy, yet via quartz-crystal microbalance measurements and predictions from molecular simulations, we show these sequences both support very similar, strong titania-binding affinities. Our molecular simulations reveal that the two sequences exhibit profoundly different modes of surface binding, with Ti-1 acting as an entropically-driven binder while Ti-2 behaves as an enthalpically-driven binder. The integrated approach presented here provides a rational basis for peptide sequence engineering to achieve the in-situ growth and organization of titania nanostructures in aqueous media and for the design of sequences suitable for a range of technological applications that involve the interface between titania and biomolecules.3

Peptide-Mediated Growth and Dispersion of Au Nanoparticles in Water via Sequence Engineering

“…We identified the range of values of ℎ ℎ and based on our previous work. 3,[5][6][7]33 The range of values between ℎ ℎ and represents an uncertainty band for which we suggest that the outcomes cannot be predicted with confidence. Figure 8 also highlights the four systems with the most inconsistency in terms of the NP stabilization assay, where the degree of confidence in our predictions is low.…”

Elucidating the Binding Mechanism of a Novel Silica-Binding Peptide

“…The binding specificity was largely due to the hydrophobic interactions between alanine (A) and leucine (L) residues of the peptide and the methyl and methine groups of the PLLA. Sultan et al [11] demonstrated that the binding of peptides to the solid surface was mediated by the ionic strength of the solvents, which further determined the nature and structure of the adsorbed peptide layer. Quartz crystal microbalance with dissipation monitoring (QCM-D) analysis performed on two distinct titanium (Ti)-binding peptides of different overall charge and hydrophobic residues showed that while water as the solvent leads to the formation of viscoelastic multilayers on the surface, a 0.15 M NaCl saline solution directed the formation of a rigid monolayer on the surface for both the peptides studied.…”

Improved Sampling in Ab Initio Free Energy Calculations of Biomolecules at Solid–Liquid Interfaces: Tight-Binding Assessment of Charged Amino Acids on TiO2 Anatase (101)

“…The binding free energy is ∆F ads = 12.1 kJ mol −1 from Equation (5) (or 17.2 kJ mol −1 via Equation (6)). CMD simulations have reported similar values of the binding free energy when the COO − -group is in direct contact to the surface [58] and via surface hydroxyls [59]. A water-mediated adsorption mode has not been found due to the weak nature of this interaction in classical models.…”