Abstract
The association of proteins and peptides with inorganic material has vast technological potential. An understanding of the adsorption of peptides at liquid/solid interfaces on a molecular-level is fundamental to fully realising this potential. Combining our prior work along with the statistical analysis of 100+ molecular dynamics simulations of adsorption of an experimentally identified graphite binding peptide, GrBP5, at the water/graphite interface has been used here to propose a model for the adsorption of a peptide at a liquid/solid interface. This bottom-up model splits the adsorption process into three reversible phases: biased diffusion, anchoring and lockdown. Statistical analysis highlighted the distinct roles played by regions of the peptide studied here throughout the adsorption process: the hydrophobic domain plays a significant role in the biased diffusion and anchoring phases suggesting that the initial impetus for association between the peptide and the interface may be hydrophobic in origin; aromatic residues dominate the interaction between the peptide and the surface in the adsorbed state and the polar region in the middle of the peptide affords a high conformational flexibility allowing strongly interacting residues to maximise favourable interactions with the surface. Reversible adsorption was observed here, unlike in our prior work focused on a more strongly interacting surface. However, this reversibility is unlikely to be seen once the peptide-surface interaction exceeds 10 kcal mol(-1).
Highlights
Eliciting greater fundamental understanding from experiment alone is challenging because the methods do not give explicit molecular-level insight into the nature of the protein adsorption mechanism
Statistical analysis highlighted the distinct roles played by regions of the peptide studied here throughout the adsorption process: the hydrophobic domain plays a significant role in the biased diffusion and anchoring phases suggesting that the initial impetus for association between the peptide and the interface may be hydrophobic in origin; aromatic residues dominate the interaction between the peptide and the surface in the adsorbed state and the polar region in the middle of the peptide affords a high conformational flexibility allowing strongly interacting residues to maximise favourable interactions with the surface
Statistical analysis of the adsorption process in conjunction with previously reported work[44,56] has led to development of an adsorption model for peptide adsorption at liquid/solid interfaces which includes the interaction of the peptide with the interfacial water molecules and not just the solid surface directly
Summary
Eliciting greater fundamental understanding from experiment alone is challenging because the methods do not give explicit molecular-level insight into the nature of the protein adsorption mechanism. The ubiquitous Langmuir model[21,22,23] and modifications thereof[24,25,26] assume, amongst other things, no lateral interaction between adsorbed peptides and reversible adsorption. Another common thread of the numerous protein adsorption models is their neglect of the biomolecule behaviour as it approaches the interface; 5192 | Soft Matter, 2015, 11, 5192--5203
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