Oligothiophene Versus β‐Sheet Peptide: Synthesis and Self‐Assembly of an Organic Semiconductor‐Peptide Hybrid

Abstract

Investigation of self-organization behavior of organic (semi)-conductors became very important recently, since their physical properties and performance in organic electronic devices strongly depend on ordering effects, on both molecular and nanoscale levels. [1] In this respect, bioinspired functionalization of conjugated systems might greatly enhance the diversity of electronically interesting assemblies, and potentially allow for the rational design of hierarchically ordered nanostructures.[2] Thus, from possible hybrids of conjugated backbones, the combination of oligo-or polythiophenes with biomolecules, such as nucleotides, [3] carbohydrates, [4] or peptides, [5] are interesting. Particularly, the latter appears to be attractive, because interplay between different intermolecular forces in the peptide and oligothiophene segments results in competing self-assembly motifs. Hence, very specific organization properties can be expected. Whereas thiophene-based materials typically form well-organized 2D lamellar superstructures due to van der Waals interactions of alkyl side chains, and stack into the third dimension via p-p interactions, [6] secondary structures of peptides, preferentially bsheets or a-helices, are governed by stronger and directed hydrogen-bond formation.[7] The high tendency of peptides to adopt well-defined secondary-structure motifs has been exploited recently to guide self-organization of a broad range of synthetic polymers.[8] Attention has mainly been devoted to the b-sheet motif, leading to anisotropic fibrillar or fiber-like structures. [9] However, other highly interesting assembly motifs, for example the coiled-coil motif, were exploited, resulting in distinct nanoobjects by the lateral assembly of amphiphilic a-helices. [10] We recently presented the first conjugate between a regioregularly alkylated quaterthiophene and a pentapeptide consisting of a silk-inspired sequence of alanine-glycine repeats, which is known to adopt b-sheet structures.[5a] Unexpected and novel 3D nanostructures were found, suggesting that short peptide sequences may indeed influence the nanoscale structure, and ultimately, properties of organic semiconducting materials.The versatility of this class of hybrid oligo-/polymers is certainly not exploited, considering the diversity of both the conjugated oligo-/polymer platforms and the bioorganic segments. It becomes increasingly evident that such materials will envelop by far more structural and functional space as, for example, common AB-block copolymer systems.[11]Here, we present the synthesis and self-organization behavior of a symmetrically substituted A-B-A-type bioinspired semiconductor, quaterthiophene-peptide hybrid 8 (Scheme 1b), by combining a central quaterthiophene segment (B) with two peptide-poly(ethylene oxide) bioconjugates (A).As outlined in Scheme 1, the oligothiophene segment was substituted on both sides with an amino acid sequence Gly-(ThrVal) 3 -Gly-aPhe-Gly (Scheme 1, structure 2), with Gly ¼ glycine, Val ¼ valine, Thr ¼ threonine, ...

A clickable, highly soluble oligopeptide that easily forms organogels

“…For instance, GAGA sequence, presented in silk protein as the repeating unit, forms antiparallel b-sheet structures by self-assembly (4 -6). It was used to adjust the nanostructure of conventional synthetic polymers (7)(8)(9) and p-conjugated oligomers (10)(11)(12)(13)(14). These reports strongly supported the use of oligopeptides as versatile building blocks for facilitating self-assembled supramolecular structures with definite properties.…”

Biotransformation on Polymer–Peptide Conjugates: A Versatile Tool to Trigger Microstructure Formation

“…The translation of the biomimetic concept of "structure-based functions" would allow complex functional systems to be realized. [2,3] Bioconjugates can possess enzymatic activity, directed conductivity, or provide active interfaces to biological systems. [3,4] They can control silicification and crystallization processes, can mimic transmembrane channel systems or interact with a pharmaceutically relevant entity for drugdelivery applications.…”

“…[2,3] Bioconjugates can possess enzymatic activity, directed conductivity, or provide active interfaces to biological systems. [3,4] They can control silicification and crystallization processes, can mimic transmembrane channel systems or interact with a pharmaceutically relevant entity for drugdelivery applications. [5] While the generation of specific functions in bioconjugates has been the focus of recent work, the control and regulation of such functions is now important.…”

Biotransformation an Polymer‐Peptid‐Konjugaten – ein universelles Werkzeug zur Mikrostrukturkontrolle

“…Dies könnte die Übertragung des biomimetischen Konzepts "Struktur erzeugt Funktion" und damit die Realisierung komplexer funktionaler Systeme ermöglichen. [2,3] Darüber hinaus können Biokonjugate enzymatisch aktiv sein, gerichtete Leitfähigkeit erzeugen oder bioaktive Oberflächen generieren. [3,4] Des Weiteren eignen sie sich zur Steuerung der Silicatmorphogenese und von Kristallisationsprozessen, sie können transmembrane Kanalsysteme nachahmen, aber auch als Wirkstofftransporter für pharmazeutisch aktive Substanzen dienen.…”

“…[2,3] Darüber hinaus können Biokonjugate enzymatisch aktiv sein, gerichtete Leitfähigkeit erzeugen oder bioaktive Oberflächen generieren. [3,4] Des Weiteren eignen sie sich zur Steuerung der Silicatmorphogenese und von Kristallisationsprozessen, sie können transmembrane Kanalsysteme nachahmen, aber auch als Wirkstofftransporter für pharmazeutisch aktive Substanzen dienen. [5] Bisher hat bei Biokonjugaten die Erzeugung spezifischer Funktionen im Vordergrund gestanden, doch nun spielt die Regulierung dieser Funktionen eine zunehmend wichtigere Rolle.…”