Temperature and force dependence of nanoscale electron transport via the Cu protein azurin

Wenjie Li, Lior Sepunaru, Nadav Amdursky, Sidney R. Cohen, Israel Pecht, Mordechai Sheves, David Cahen

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56 Scopus citations


Solid-state electron transport (ETp) via a monolayer of immobilized azurin (Az) was examined by conducting probe atomic force microscopy (CP-AFM), as a function of both temperature (248-373K) and applied tip force (6-15 nN). At low forces, ETp via holo-Az (with Cu2+) is temperature-independent, but thermally activated via the Cu-depleted form of Az, apo-Az. While this observation agrees with those of macroscopic-scale measurements, we find that for holo-Az the mechanism of ETp at high temperatures changes upon an increase in the force applied by the tip to the proteins; namely, above 310 K and forces >6 nN ETp becomes thermally activated. This is in contrast to apo-Az, where increasing applied force causes only small monotonic increases in currents due to decreased electrode separation. The distinct ETp temperature dependence of holo- and apo-Az is assigned to a difference in structural response to pressure between the two protein forms. An important implication of these CP-AFM results (of measurements over a significant temperature range) is that for reliable ETp measurements on flexible macromolecules, such as proteins, the pressure applied during the measurements should be controlled or at least monitored.

Original languageEnglish
Pages (from-to)10816-10824
Number of pages9
JournalACS Nano
Issue number12
StatePublished - 21 Dec 2012
Externally publishedYes


  • Arrhenius activation energy
  • azurin
  • biomolecular electronics
  • conductivity
  • electron transport
  • nanometer scale
  • tunneling


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