Yeast cytochrome c on gold electrode: a robust hybrid system for bio-nanodevices

Yeast cytochrome c has been directly self-chemisorbed on bare gold electrodes via its native free sulphur-containing group Cys102. Topological, spectroscopic and electron transfer properties of immobilised molecules have been investigated by in situ scanning probe microscopy and cyclic voltammetry. Atomic force and scanning tunnelling microscopy reveal individual protein molecules adsorbed on the gold substrate, with no evidence of aggregates. The electrical conductivity has been investigated also by conductive atomic force microscopy. The adsorbed proteins appear firmly bound to gold and display dimensions in good agreement with crystallographic data. Cyclic voltammetry analysis shows that the electrode surface is functionalised with electro-active proteins, at high coverage, with a measured redox midpoint potential in good agreement with the formal potential. Additionally, the vibrational features of the cytochrome adsorbed on gold have been studied by surface enhancement Raman spectroscopy. Our results clearly indicate that this variant of cytochrome c adsorbs on bare gold electrodes preserving morphological properties and redox functionality.