"Electronic transport through apo- and holoferritin".

"Electronic transport through apo- and holoferritin".

The incredible molecular architectures seen in many protein molecules, responsible for numerous biological functions, can provide inspiration for synthetic design. Perhaps an even more exciting prospect – potentially offering immediate access to biological attributes – is the direct exploitation of biological species via successful interfacing with an electronic device.

The Jason Davis group in Oxford is exploring bio-recognition and sensing along with novel materials for molecular electronics including biomolecules. Ferritin is an interesting iron-storage protein, central to the control of iron chemistry within the cell. It is a relatively large and robust protein that could serve as a paradigm for a biomolecule-based device. The present work demonstrates how the electronic properties of the ferritin protein change dramatically depending on the presence or absence of the central mineral core. We have also shown how the electronic behaviour can be linked to the contrasting mechanical properties of the core and the protein.

We hope that our understanding of the mechanism of charge transfer in large biomolecules, fundamental to essential biological processes, will advance – thus providing the knowledge necessary for successful bio-electronic interfacing and improved synthetic models exploiting some of nature’s advanced chemistry.

Conductive probe atomic force microscopy (CP-AFM) has been used to investigate electronic transport through the protein ferritin in both its holo and apo forms. The presence of the iron oxide core has a notable effect on both conductance and the molecular response to probe-induced compression. This response can also be contrasted with that of the much smaller metalloprotein cytochrome c, across which electron transport can be simulated by a single non-resonant tunnel barrier model. Tapping mode AFM imaging, in different compressional regimes, reveals both the mineral core of holoferritin and significant collapse of the hollow protein cavity of apoferritin. These topographic findings correlate well with CP-AFM conductance data and facilitate a clearer description of electron transport across these molecules.

Electron flux through apo-and holoferritin.

Danny N Axford and Jason J Davis.

Nanotechnology 18 (2007) 145502 (7pp).

doi:10.1088/0957-4484/18/14/145502.