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Chemphyschem : a European journal of chemical physics and physical chemistry

Probing peptide-inorganic surface interaction at the single molecule level using force spectroscopy.


PMID 21488141

Abstract

We investigate the interaction between D-Ala-D-Ala peptide and a stainless steel (SS) surface by AFM force spectroscopy with view to understand the role and nature of interfacial processes at the single molecule level. For this purpose, force-distance curves were recorded between the D-Ala-D-Ala modified tip and the SS surface in NaHCO(3)-enriched medium. The SS surface was prepared in a way that allows iron oxide species, presumably FeOOH, to be formed and remains stable during AFM measurements. Dynamic force measurements show that the unbinding force linearly increases with the logarithm of the loading rate, as generally observed for receptor–ligand complexes. Our results reveal also the existence of two regimes, suggesting the presence of multiple energy barriers in the energy landscape. From these dynamic force spectroscopy measurements, the kinetic off-rate constant is determined. An average unbinding force in the range of 50-300 pN is obtained, depending on the loading rate. Accordingly, in a medium in which the electrostatic interactions are not dominating, the binding mechanism of the peptide and SS surface cannot be attributed to covalent bonds and may be due to a combination of van der Waals and hydrogen bonds. Our findings open up new way to probe peptide-inorganic surface interactions and to understand the mechanism of peptide specific binding which is of particular interest in the design of hybrid materials.

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