Electron flux through apo- and holoferritin

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.