Tuning electronic transport via hepta-alanine peptides junction by tryptophan doping.
Charge migration for electron transfer via the polypeptide matrix of proteins is a key process in biological energy conversion and signaling systems. It is sensitive to the sequence of amino acids composing the protein and, therefore, offers a tool for chemical control of charge transport across biomaterial-based devices. We designed a series of linear oligoalanine peptides with a single tryptophan substitution that acts as a "dopant," introducing an energy level closer to the electrodes' Fermi level than that of the alanine homopeptide. We investigated the solid-state electron transport (ETp) across a self-assembled monolayer of these peptides between gold contacts. The single tryptophan "doping" markedly increased the conductance of the peptide chain, especially when its location in the sequence is close to the electrodes. Combining inelastic tunneling spectroscopy, UV photoelectron spectroscopy, electronic structure calculations by advanced density-functional theory, and dc current-voltage analysis, the role of tryptophan in ETp is rationalized by charge tunneling across a heterogeneous energy barrier, via electronic states of alanine and tryptophan, and by relatively efficient direct coupling of tryptophan to a Au electrode. These results reveal a controlled way of modulating the electrical properties of molecular junctions by tailor-made "building block" peptides.
Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel 76100; Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel 76100;
Cunlan
C
Guo
Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel 76100;
Xi
X
Yu
Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel 76100;
Sivan
S
Refaely-Abramson
Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel 76100; Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel 76100;
Lior
L
Sepunaru
Department of Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel 76100;
Tatyana
T
Bendikov
Department of Immunology, Weizmann Institute of Science, Rehovot, Israel 76100.
Israel
I
Pecht
Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel 76100;
Leeor
L
Kronik
Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel 76100;
Ayelet
A
Vilan
Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel 76100;
Mordechai
M
Sheves
Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel 76100; david.cahen@weizmann.ac.il.
David
D
Cahen
D000409:Alanine / Q000737:chemistry*; D004560:Electricity; D004583:Electrons; D008962:Models, Theoretical; D010455:Peptides / Q000737:chemistry*; D013696:Temperature; D014364:Tryptophan / Q000737:chemistry*
D010455:Peptides; D014364:Tryptophan; D000409:Alanine
doping; electron transport; inelastic electron tunneling spectroscopy; oligopeptide; self-assembled monolayer