Charge transport in vertically aligned, self-assembled peptidenanotube junctions

Abstract

The self-assembly propensity of peptides has been extensively utilized in recent years for the formation of supramolecular nanostructures. In particular, the self-assembly of peptides into fibrils and nanotubes makes them promising building blocks for electronic and electro-optic applications. However, the mechanisms of charge transfer in these wire-like structures, especially in ambient conditions, are not yet fully understood. We describe here a layer-by-layer deposition methodology of short self-assembled cyclic peptide nanotubes, which results in vertically oriented nanotubes on gold substrates. Using this novel deposition methodology, we have fabricated molecular junctions with a conductive atomic force microscopy tip as a second electrode. Studies of the junctions' current-voltage characteristics as a function of the nanotube length revealed an efficient charge transfer in these supramolecular structures, with a low current attenuation constant of 0.1 Å(-1), which indicate that electron transfer is dominated by hopping. Moreover, the threshold voltage to field-emission dominated transport was found to increase with peptide length in a manner that depends on the nature of the contact with the electrodes. The flexibility in the design of the peptide monomers and the ability to control their sequential order over the nanotube by means of the layer-by-layer assembly process, which is demonstrated in this work, can be used to engineer the electronic properties of self-assembled peptide nanotubes toward device applications.

Anti-amyloidogenic Heterocyclic Peptides

“…As implied by its name, the fibril formation inhibitor cyclic peptide, cyc [60][61][62][63][64][65][66][67][68][69][70] (Fig. 7c), has two contrasting faces, one hydrophobic and the other hydrophilic [98,102].…”

“…Atomic force microscopy (AFM), CD spectroscopy, and EM showed that no amyloid fibrils were formed upon aging of cyclo 17,21 ]Aβ (1-28) contained higher amounts of α-helical structures than Aβ28 and that the two ]Aβ (1-28), a cyclic derivative of a full-length Aβ [97]. (c) Ribbon and CPK representation of the Janus cyclic peptide cyc [60][61][62][63][64][65][66][67][68][69][70] showing the persistent intramolecular backbone hydrogen bonds in blue [98] Anti-amyloidogenic Heterocyclic Peptides peptides interacted to prevent the generation of Aβ amyloid. Moreover, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay suggested that cyclo 17,21 -[Lys 17 ,Asp 21 ]Aβ(1-28) protected human glioblastoma/astrocytoma cells from Aβ28-induced toxicity.…”

“…7c), has two contrasting faces, one hydrophobic and the other hydrophilic [98,102]. Cyc [60][61][62][63][64][65][66][67][68][69][70] was derived from the amyloidogenic sequence of human apolipoprotein C-II (apoC-II), which self-assembles readily into fibrils upon removal of the lipid component. ApoC-II has been identified in amyloid plaques [103] and, together with Aβ40, was demonstrated to induce macrophage inflammatory response and initiate early events in heart disease [104].…”

“…Consequently, the external dimensions and surface of cyclic D,L-α-peptide nanotubes are relatively easy to control through a rational choice of amino acid side chains and size prior to the synthesis of the cyclic peptide ring. An approach based on chemical synthesis opens the door for the design of a wide range of cyclic D,L-α-peptides to produce tubular structures with specific characteristics and various possible applications [2,[55][56][57][58][59][60].…”

Formation of Ordered Biomolecular Structures by the Self-assembly of Short Peptides

“…These assemblies have been exploited for applications of biosensing, drug delivery, molecular electronics, etc. [38][39][40][41][42][43][44][45] This paper describes the experimental steps needed in order to start the spontaneous self-assembly of homoaromatic peptides. In addition, it presents the process of peptide coassembly.…”