Conductance Titration of Single-Peptide Molecules

Abstract

We have measured the conductance of single peptides covalently bonded to two Au electrodes via S-Au bonds by repeatedly forming a large number of molecular junctions. The conductance decreases exponentially with the peptide length, with a decay constant of beta = 0.9 +/- 0.1 A-1, suggesting that tunneling is the mechanism of electron transport in the peptides. The conductance of the peptides is sensitive to the solution pH, due to the protonation/deprotonation of the amine and carboxyl groups of the peptides, which provides titration measurements based on single-molecule conductance.

Metal complexes in molecular junctions

“…33 In conclusion, as a high level of functionality may be integrated into a molecular system permitting redox or…”

Forces from periodic charging of adsorbed molecules

“…Very often such experiments are conducted in a so-called break-junction setup, [9][10][11][12][13][14][15][16][17][18][19][20] as also reported in several articles of this special issue. Scanning tunneling microscopy (STM) also provides the possibility to contact single molecules and to characterize the current flow across the junction.…”

“…Scanning tunneling microscopy (STM) also provides the possibility to contact single molecules and to characterize the current flow across the junction. [21][22][23][24][25][26][27] Both approaches have their own advantages, for example, gating can be achieved much easier in a break-junction setup, [16][17][18][19][20] whereas STM offers the atomic-scale characterization of the junction prior to contacting. [24][25][26][27] However, also experiments that do not involve a contacting of molecules to leads can provide insight into molecular electronics.…”

Long-range protein electron transfer observed at the single-molecule level: In situ mapping of redox-gated tunneling resonance

“…Understanding of charge transfer mechanisms has mostly been based on average results of macroscopic measurements. The advent of scanning probe microscopies, along with other supersensitive techniques, has made it possible to characterize or directly observe charge transfer through organic molecules down to the nanoscale and single-molecule levels, as illustrated by measurements of singlemolecule conductivity (17)(18)(19)(20)(21) and probing of molecular switching and resonant tunneling (22,23). This, however, remains a daunting challenge for proteins, with difficulties arising from the assembly of suitable structures with sufficient stability, the retention of biological functions at interfaces, and the control of molecular orientations on solid surfaces.…”