Near-Metallic Behavior of Warm Holoferritin Molecules on a Gold(111) Surface

Abstract

Ferritin, the iron-storage protein, holds great potential for bioelectronic applications because of the presence of an electronically conducting iron core. We have applied scanning tunneling microscopy (STM), a high-resolution imaging method based on direct tunneling, to visualize the ferritin molecules both in the iron-containing holo form and in the iron-free apo form, and we have probed the electron flow through the two forms of this protein by measuring the current-voltage response using scanning tunneling spectroscopy (STS). Clear distinctions could be made among the current-voltage responses of the metallic gold(111) substrate surface, holoferritin molecules, and apoferritin molecules at room temperature. When warmed to the near-physiological temperature of 40 °C, the current-voltage response of the holoferritin molecules exhibited no band gap resembling near-metallic behavior, and the apoferritin molecules exhibited only a reduced band gap.

Temperature and Force Dependence of Nanoscale Electron Transport via the Cu Protein Azurin

“…If a low force is applied at room temperature, the observed current across apo-Az junctions at 1 V was an order of magnitude lower than that across the holo-Az junctions (Fig 3, black curve). This difference resembles that obtained in our macroscopic measurements 21 and is qualitatively consistent with results of conduction measurements via another metal-containing protein (Ferritin) by CP-AFM 27 , STM 38 or, for Az in a three-terminal configuration. 39 This decrease in current magnitude highlights the role of the Cu ion as an efficient ET and ETp mediator in Az.…”

Solid-state electron transport in Mn-, Co-, holo-, and Cu-ferritins: Force-induced modulation is inversely linked to the protein conductivity

“…In fact, Axford et al reported earlier that the single-barrier Simmons model could not reasonably explain the conductance behavior of holoferritin due to presence of the metal core that introduces an additional tunnel barrier [34]. On the other hand, in some previous reports, it was shown that the I-V traces of ferritin protein systems could be well-fitted to the F-N equation [25,31,37]. Therefore, in the present study, the F-N equation was used to fit the I-V responses for the five ferritin systems across a range of applied forces (Fig.…”

Mechanical properties of nucleoprotein complexes determined by nanoindentation spectroscopy

“…AFM samples are prepared usually by the droplet cast method [ 28 , 29 ] on muscovite mica since it offers atomically flat surface. Depending on the type of application, gold on mica [ 23 , 30 – 32 ] substrates is occasionally used. The sample should be properly adhered to the underlying substrate by electrostatic attraction or by covalent binding in order to withstand the raster scanning by the cantilever.…”