AVS 58th Annual International Symposium and Exhibition
    Biomaterial Interfaces Division Monday Sessions
       Session BI-MoM

Paper BI-MoM11
Solid State Electron Transport across Proteins

Monday, October 31, 2011, 11:40 am, Room 108

Session: Biomolecules at Interfaces
Presenter: David Cahen, Weizmann Institute of Science, Israel
Authors: D. Cahen, Weizmann Institute of Science, Israel
M. Sheves, Weizmann Institute of Science, Israel
I. Pecht, Weizmann Institute of Science, Israel
L. Sepunaru, Weizmann Institute of Science, Israel
Correspondent: Click to Email
We found that solid-state electron transport (Etp) studies are possible across non-modified 'dry' proteins, between two solid electrodes, using the light-induced proton pumping protein, Bacteriorhodopsin (bR), the electron transfer (ET) protein, Azurin (Az), and Bovine Serum Albumin (BSA). Clear differences between these proteins, where for bR and Az we can show that they preserve their structure in the solid state measurement configuration, were observed, with small tunneling decay constants for all three proteins, suggesting that incoherent transport is the dominant mechanism. Putting our data in perspective by comparing them to all known protein Etp data in the literature, we concluded that, in general, proteins behave more akin to molecular wires than to insulators. An important part of these studies was the modification of the proteins by, e.g., removing or disconnecting the retinal in bR and removing the Cu redox centre in Az.

We now report that, notwithstanding the above-noted earlier conclusion on hopping, which was based on the Etp efficiency, Az shows 9-360K temperature independent Etp, until its denaturation temperature. Removal of the Cu changes this behavior to Arrhenius-like thermally activated Etp, which becomes temperature independent below ~ 200K, a behavior that apo-Az shares, qualitatively with bR, its variants and with BSA.

This difference between bR and Az leads to the truly remarkable situation that above room temperature the non-ET protein bR shows significantly better Etp than ET protein Az.