Electroconductive and photocurrent generation properties of self‐assembled monolayers formed by functionalized, conformationally‐constrained peptides on gold electrodes

Abstract

The electroconductive properties and photocurrent generation capabilities of self-assembled monolayers formed by conformationally-constrained hexapeptides were studied by cyclic voltammetry, chronoamperometry, and photocurrent generation experiments. Lipoic acid was covalently linked to the N-terminus of the peptides investigated to exploit the high affinity of the disulfide group to the gold substrates. Smart functionalization of the peptide scaffold with a redox-active (TOAC) or a photosensitizer (Trp) amino acid allowed us to study the efficiency of peptide-based self-assembled monolayers to mediate electron transfer and photoinduced electron transfer processes on gold substrates. Interdigitated microelectrodes have shown higher film stability under photoexcitation, lower dark currents, and higher sensitivity with respect to standard gold electrodes.

Photocurrent generation in peptide-based self-assembled monolayers on gold electrodes

“…from the N-terminus to the C-terminus (reduction). This result is in line with ET measurements in which the oxidation process is favored as compared to the reduction process when the peptide is linked to the gold surface at the N-terminus, due to the effect of the electrostatic field associated with the helix macrodipole on the ET process [9].…”

“…A comparison between the anodic and cathodic photocurrent responses shows a sevenfold increase in the IPCE% for the anodic current compared to the cathodic one. It has already been demonstrated by our group that the rate of ET through 3 10 -helical peptides is affected by the electric field generated by the dipole of the helix [7,9]. In the case of anodic photocurrent the electrons are transferred from the C-terminus to the N-terminus (oxidation process), while for the generation of a cathodic current the direction of ET is opposite, i.e.…”

“…Photocurrent generation experiments on peptides immobilized on surfaces have become a viable alternative for studying electron transfer (ET) processes [8,9]. Suitably functionalized peptides, covalently linked to gold surfaces making use of the strong Au-S interaction (≈ 40 kcal mol −1 ), have been shown to form highly ordered SAMs [10,11] and possess peculiar electronic conduction properties in terms of long-range and directional ET.…”

Conformational Effects on the Electron‐Transfer Efficiency in Peptide Foldamers Based on α,α‐Disubstituted Glycyl Residues

“…Even if the two data sets are not strictly comparable, because of differences in the peptide sequence, the present results suggest that the 3 10 -helix has a lower effect than the a-helix on the intramolecular electron-transfer process. This observation is in agreement with recent experiments performed by electrochemical methods on 3 10 -helical peptides covalently linked to a gold surface [55], showing that the helix dipole moment affects the electron-transfer rate toward the gold substrate. Also in that case, the effect was lower in 3 10 -helical than in a-helical peptides.…”

A modular electrochemical peptide-based sensor for antibody detection

“…However, E-PB sensors often display voltammetric baseline fluctuations and capacitance current drifts 6 presumably because the recognition peptide in the unbound state cannot be considered structure-free 13 and the secondary structure of the peptide chain cannot be controlled as in the case of, for example, short DNA oligomers. 14 Moreover, E-PB sensors are difficult to generalize because redox tag labelling on the recognition peptide might lead to changes in the specificity of the antigen-antibody binding and in the signalling of the sensor. Another possible drawback of these sensors is their short-term stability.…”