We present the peptide molecules which act as a mediator for long range electron transfer. Understanding the role of peptides in bridge-mediated tunneling of electrons is essential from biological point of view but is also very important for the development of biosensors and nanotechnology. Investigation of electrical properties of single molecules is of special interest because of their potential application in molecular electronics. In some cases we observed the current rectification.

We designed and synthesized 4 thiolated peptide derivatives containing from 1 to 4 proline residues and used them for preparation of self-assembled monolayers (SAMs) on gold electrodes. The quality of the resulting layers and the SAMs coverage were examined using electrochemical impedance spectroscopy and cyclic voltammetry. The electrical behavior of gold-molecule-gold junctions incorporating these peptides was investigated using scanning tunneling spectroscopy (STS). The STS method allows to measure the conductance of a single molecule entrapped in a molecular junction. It also provides the information about the influence of the length and the secondary structure of the molecule on electron transfer efficiency. 

Fig.1 Structure of the synthesized peptide consisting of L-proline and L-cysteine with protected thiol and amine groups and a cystamine linker.

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1. Tuning Electron Transmission Efficiency through Peptides: Modulation by Mechanically Induced Structural Changes
2. Rectification behavior of molecular junctions incorporating peptides