Investigation of a structure of new functional peptide composite materials with gold nanoparticles

Abstract

A structure of new composite coatings formed at room temperature from dispersions of gold nanoparticles (NPs) in an aqueous solution of a peptide (PT) Asp-Glu-Val-Asp-Trp-Phe-Asp on mica, glass, silicon, aluminum, and gold substrates was investigated by IR spectroscopy, microprobe and laser interference microscopy, and dynamic light scattering. The size of gold NPs in the solution is 40 nm. It has been established that an individual PT crystallizes, forming various structures, the character of which significantly depends on the substrate nature, surface conditions, and pH value of the medium. At pH ∼ 9, a zwitterionic state of the PT molecule breaks down and its isomeric form changes (from trans-to cis-configuration). As a result, the forming peptide layer becomes disordered and the layer growth mechanism changes from lateral to a normal one. Globular and fibrillar structures form in the composite layers adjacent to the substrate, and peptide layers with complicated morphology (dendrites and spherulites) grow above them. The shapes and sizes of gold NPs in the coatings and differences in the structure of PT composite coatings formed with gold and silver NPs have been discussed. The conclusion has been drawn that crystallization of NPs and nanocomposite coatings can be controlled by changing the electric charge of the peptide molecule.