Adsorption and self-assembly of a ferrocene d- and l-nonapeptide disulfide onto gold and mica substrates

Abstract

A ferrocene-conjugated nonapeptide composed of alternating D- and L-residues and containing two sulfide linkages was synthesized (_LCys-_DPhe-_LPhe-_DPhe-(Ferrocene)_LLys-_DAla-_LAsp-_DAla-_LCys-NH₂) as novel material for nanostructure formation. The cyclic nonapeptide assembly onto gold was highly disordered and included a large dead volume on the gold surface. Also, a large proportion of ferrocene units (79%) were located in microenvironments where electron transfer was hindered. On the other hand, two kinds of self-assembled nanostructure morphologies: linear and ring were observed on mica, depending on the age of the peptide solution used in the adsorption process. Linear nanostructures, 100–1000 nm in length and 1.4–4.0 nm in height, were observed by AFM when using freshly prepared peptide solutions. Rings, 100–200 nm in diameter and 1.6 nm in height, were obtained when using a 2-month aged peptide solution.