Self-Assembled Dual Helical Nanofibers of Amphiphilic Perylene Diimides with Oligopeptide Substitution

Self-Assembled Metal-Coordination Nanohelices as Efficient and Robust Chiral Supramolecular Catalysts for Enantioselective Reactions

The development of chiral nanostructures-based supramolecular catalysts with satisfied enantioselectivity remains a significantly more challenging task. Herein, the synthesis and self-assembly of various amino acid amphiphiles as chiral supramolecular catalysts after metal ion coordination is reported and systematically investigate their enantioselectivity in asymmetric Diels-Alder reactions. In particular, the self-assembly of l/d-phenylglycine-based amphiphiles (l/d-PhgC16) and Cu(II) into chiral supramolecular catalysts in the methanol/water solution mixture is described, which features the interesting M/P nanohelices (diameter ≈8 nm) and mostly well-aligned M/P nanoribbons (NRs). The M/P supramolecular catalysts show both high but inverse enantioselectivity (>90% ee) in Diels-Alder reactions, while their monomeric counterparts display nearly racemic products. Analysis of the catalytic results suggests the outstanding enantioselectivities are closely related to the specific stereochemical microenvironment provided by the arrangement of the amphiphiles in the supramolecular assembly. Based on the experimental evidence of chirality transfer from supramolecular nanohelices to coordinated Cu(II) and substrate aza-chalcone and the molecular dynamics simulations, the enantioselective catalytic mechanisms are proposed. Moreover, the relationships between molecular structures of amino acid amphiphiles (the hydrophilic head group and hydrophobic alkyl chain length) in supramolecular catalysts and enantioselectivity in Diels-Alder reactions are elaborated.

Kinetic Controlled Chirality Transfer and Induction in 2D Hydrogen-Bonding Assemblies of Glycylglycine on Au(111)

Chirality transfer is of vital importance that dominates the structure and functionality of biological systems and living matters. External physical stimulations, e.g. polarized light and mechanical forces, can trigger the chirality symmetry breaking, leading to the appearance of the enantiomeric entities created from a chiral self-assembly of achiral molecule. Here, several 2D assemblies with different chirality, synthesized on Au(111) surface by using achiral building blocks - glycylglycine (digly), the simplest polypeptide are reported. By delicately tuning the kinetic factors, i.e., one-step slow/rapid deposition, or stepwise slow deposition with mild annealing, achiral square hydrogen-bond organic frameworks (HOF), homochiral rhombic HOF and racemic rectangular assembly are achieved, respectively. Chirality induction and related symmetry broken in assemblies are introduced by the handedness (H-bond configurations in principle) of the assembled motifs and then amplified to the entire assemblies via the interaction between motifs. The results show that the chirality transfer and induction of biological assemblies can be tuned by altering the kinetic factors instead of applying external forces, which may offer an in-depth understanding and practical approach to peptide chiral assembly on the surfaces and can further facilitate the design of desired complex biomolecular superstructures.

Semiconductive and Biocompatible Nanofibrils from the Self-Assembly of Amyloid π-Conjugated Peptides

Owing to their capacity to self-assemble into organized nanostructures, amyloid polypeptides can serve as scaffolds for the design of biocompatible semiconductive materials. Herein, symmetric and asymmetric amyloid π-conjugated peptides were prepared through condensation of perylene diimide (PDI) with a natural amyloidogenic sequence derived from the islet amyloid polypeptide. These PDI-bioconjugates assembled into long and linear nanofilaments in aqueous solution, which were characterized by a cross-β-sheet quaternary organization. Current-voltage curves exhibited a clear signature of semiconductors, whereas the cellular assays revealed cytocompatibility and potential application in fluorescence microscopy. Although the incorporation of a single amyloid peptide appeared sufficient to drive the self-assembly into organized fibrils, the incorporation of two peptide sequences at the PDI's imide positions significantly enhanced the conductivity of nanofibril-based films. Overall, this study exposes a novel strategy based on amyloidogenic peptide to guide the self-assembly of π-conjugated systems into robust, biocompatible, and optoelectronic nanofilaments.

Supramolecular Nanostructures Based on Perylene Diimide Bioconjugates: From Self-Assembly to Applications

Self-assembling π-conjugated systems constitute efficient building blocks for the construction of supramolecular structures with tailored functional properties. In this context, perylene diimide (PDI) has attracted attention owing to its chemical robustness, thermal and photo-stability, and outstanding optical and electronic properties. Recently, the conjugation of PDI derivatives to biological molecules, including oligonucleotides and peptides, has opened new avenues for the design of nanoassemblies with unique structures and functionalities. In the present review, we offer a comprehensive summary of supramolecular bio-assemblies based on PDI. After briefly presenting the physicochemical, structural, and optical properties of PDI derivatives, we discuss the synthesis, self-assembly, and applications of PDI bioconjugates.

Rational Design of Chiral Nanohelices from Self-Assembly of Meso-tetrakis (4-Carboxyphenyl) Porphyrin-Amino Acid Conjugates

In this article, meso-tetrakis (4-carboxyphenyl) porphyrins modified with different amino acids were designed, synthesized, and researched. The chiral self-assembly behavior of these porphyrin-amino acid molecules can be precisely controlled by adjusting the pH, constituent amino acids, and temperature, thereby giving rise to chiral nanostructures with precisely tailored helical pitch and handedness. This research provides a certain reference for the design and preparation of chiral nanomaterials and has potential application prospects in chiral resolution and chiral catalysis.

Self-Assembling Hydrogel Structures for Neural Tissue Repair

Hydrogel materials have been employed as biological scaffolds for tissue regeneration across a wide range of applications. Their versatility and biomimetic properties make them an optimal choice for treating the complex and delicate milieu of neural tissue damage. Aside from finely tailored hydrogel properties, which aim to mimic healthy physiological tissue, a minimally invasive delivery method is essential to prevent off-target and surgery-related complications. The specific class of injectable hydrogels termed self-assembling peptides (SAPs), provide an ideal combination of in situ polymerization combined with versatility for biofunctionlization, tunable physicochemical properties, and high cytocompatibility. This review identifies design criteria for neural scaffolds based upon key cellular interactions with the neural extracellular matrix (ECM), with emphasis on aspects that are reproducible in a biomaterial environment. Examples of the most recent SAPs and modification methods are presented, with a focus on biological, mechanical, and topographical cues. Furthermore, SAP electrical properties and methods to provide appropriate electrical and electrochemical cues are widely discussed, in light of the endogenous electrical activity of neural tissue as well as the clinical effectiveness of stimulation treatments. Recent applications of SAP materials in neural repair and electrical stimulation therapies are highlighted, identifying research gaps in the field of hydrogels for neural regeneration.

Chiral Supramolecular Polymers Assembled by Amphiphilic Oligopeptide-Perylene Diimides and High Electrochemical Sensing

Various secondary structures, for example, β-sheet hydrogen bonds formed by oligopeptides exhibiting high directionality and selectivity provide a new avenue to regulate optoelectronic performances of supramolecular assemblies constructed by π-conjugated chromophores. In this work, oligopeptide-perylene diimides (AUPDIs) are synthesized to generate β-sheet strands which guide the formation of chiral supramolecular polymers with a diversity of morphologies in combination with the π-π stacking even in aqueous media. Complex morphology transitions are successfully controlled by simply adjusting the water volume fraction in the binary solvent of water and tetrahydrofuran from spherical hollow aggregates to long helical nanowires and to short nanofibers. The mechanism of the assembly changes from cooperative to the isodesmic model relying on AUPDI concentrations. This originates from the transformation in the β-sheet that regulates profoundly the arrangement of the AUPDI molecules. Prominently efficient and positive electronic sensing to triethylamine for highly helical nanowires engenders due to the highly ordered helical arrangement within the nanowires, fourfold of the short nanofibers.

Hierarchical self-assemblies of carnosine asymmetrically functioned perylene diimide with high optoelectronic response

HYPOTHESIS

Taking advantage of photoinduced electron transfer, one dimensional organic nanomaterials with tunable donor-acceptor (D-A) interface provide a promising avenue to get high optoelectric properties. However, strong charge transfer interaction between D and A segments impedes the formation of long-range ordered structure, which limits the charge transport through efficient π electronic delocalization. Incorporation of chiral peptide offering various hydrogen bonding (H-bonding) along with asymmetric molecular structure enables substantially controllable D-A interface and tunable organization of the π-conjugates.

EXPERIMENTS

A new amphiphilic perylene diimide (CUPDI) with PDI as an acceptor is designed and synthesized. A polar chiral dipeptide composed of β-alanine and l-histidine with the imidazole ring as the donor i.e., l-carnosine, is incorporated at one of imides. Transition of various supramolecular assemblies of CUPDI is realized by changing CUPDI concentration and solvents. The photoelectronic properties of the assemblies are investigated as well as their association with the microstructure of the nanomaterials.

FINDINGS

Delicately tuned hydrogen bonds between the peptides and π-π interaction between PDI cores in different solvents enable the formation of assemblies with multifarious microstructures such as small spherical aggregates, nanowires with uniform diameter, nanobelts, and irregular aggregates. The maximum amount of photocurrent enhancement is up to 1.08 µA observed for the nanobelt, four times higher than that of irregular aggregates. However, the nanowires show the best performance of 7.1-fold in response to ammonia. Thus, the photoelectric performances are strongly dependent on the the molecular arrangement within the nanomaterials.