Solvent-Induced Supramolecular Assembly of a Peptide-Tetrathiophene-Peptide Conjugate

The assembly of a peptide-tetrathiophene-peptide (PTP) conjugate has been investigated in mixed solvents, which has different polarities by changing the solvent proportions. It was found that PTP can form fibers in THF/hexane solutions with 40–80%v of hexane. The fibers were stable and did not change on time. On the other hand, PTP formed ordered structures in a mixed solution with the water content from 40 to 60%v. For the as-prepared solutions, two nanostructures vesicles and parallelogram sheets were obtained. The parallelogram sheets could transform into vesicles on time. The fibers showed supramolecular chirality, however, there was no Cotton effect for vesicles and parallelogram sheets. UV-vis, FL, XRD, FT-IR, and CD spectra together with SEM, AFM, TEM were used to characterize the nanostructures and properties of the assemblies. Molecular packing mechanism was proposed based on the experimental data.

Dynamic Modulation of Supramolecular Chirality Driven by Factors from Internal to External Levels

Supramolecular chirality, generated by the asymmetric assembly of chiral or achiral molecules, has attracted intense study owing to its potential to offer insights into natural biological structures and its crucial roles in advanced materials. The optical activity and stacking pathway of building molecules both greatly determine the chirality of the whole supramolecular structure. The flexibility of supramolecular structures makes their chirality easy to modulate through abundant means. Adjustment of the molecular structure or packing mode, or external stimuli that act like a finger gently pushing toy bricks, can greatly change the chirality of supramolecular assemblies. The dynamic regulation of chiral nanostructures on the intramolecular, intermolecular, and external levels could be regarded as the modulatory essence in numerous strategies, however, this perspective is ignored in most reviews in the literature. Herein, therefore, we focus on the ingenious dynamic modulation of chiral nanostructures by these factors. Through dynamic modulation with changes in chiroptical spectroscopy and electron microscopy, the mechanism of formation of supramolecular chirality is also elaborated.

Tetrapeptide-coumarin conjugate 3D networks based on hydrogen-bonded charge transfer complexes: gel formation and dye release

Oligopeptide-based derivatives are important synthons for bio-based functional materials. In this article, a Gly-(L-Val)-Gly-(L-Val)-coumarin (GVGV-Cou) conjugate was synthesized, which forms 3D networks in ethanol. The gel nanostructures were characterized by UV-vis spectroscopy, FT-IR spectroscopy, X-ray diffraction (XRD), SEM and TEM. It is suggested that the formation of charge transfer (CT) complexes between the coumarin moieties is the main driving force for the gel formation. The capability of the gel to encapsulate and release dyes was explored. Both Congo Red (CR) and Methylene Blue (MB) can be trapped in the CT gel matrix and released over time. The present gel might be used as a functional soft material for guest encapsulation and release.