A Lyotropic Liquid Crystal from a Flexible Oligopeptide Amphiphile in Dimethyl Sulfoxide

Peptide-based nanomaterials and their diverse applications

The supramolecular self-assembly of peptides offers a promising avenue for both materials science and biological applications. Peptides have garnered significant attention in molecular self-assembly, forming diverse nanostructures with α-helix, β-sheet, and random coil conformations. These self-assembly processes are primarily driven by the amphiphilic nature of peptides and stabilized by non-covalent interactions, leading to complex nanoarchitectures responsive to environmental stimuli. While extensively studied in biomedical applications, including drug delivery and tissue engineering, their potential applications in the fields of piezoresponsive materials, conducting materials, catalysis and energy harvesting remain underexplored. This review comprehensively elucidates the diverse material characteristics and applications of self-assembled peptides. We discuss the multi-stimuli-responsiveness of peptide self-assemblies and their roles as energy harvesters, catalysts, liquid crystalline materials, glass materials and contributors to electrical conductivity. Additionally, we address the challenges and present future perspectives associated with peptide nanomaterials. This review aims to provide insights into the versatile applications of peptide self-assemblies while concisely summarizing their well-established biomedical roles that have previously been extensively reviewed by various research groups, including our group.

Self-Assembly of a Perfluorinated Amphiphilic Cyanine Dye into Branched Tubular J-Aggregates

The self-assembly process is governed by the individual constituents of molecules through precise non-covalent interactions. Amphiphilic cyanines are intriguing in supramolecular chemistry due to the large polarizability of their delocalized π-electron systems, their tuneable optical properties and their ability to form well-defined self-assembled structures in different media. Here we present the synthesis of a novel tetrahydroxy amphiphilic carbocyanine dye with perfluoro alkylated chains -(CH2)2-(CF2)5-CF3 as hydrophobic segments and aminoproanediol as hydrophilic segment. The target molecule was synthesized in a multi-step process, which illustrates the complexity and precision required to achieve the desired structure. This study focuses on the comparison of the influence of C8H17 and C8H4F13 tails and the effects of carboxylated and non-ionic aminopropanediol head groups as substituents on self-assembly of the TBC dye. Absorption and fluorescence measurements show similar spectroscopic properties to cyanine dyes studied previously. Cryogenic transmission electron microscopy (cryo-TEM) reveals formation of multiple supramolecular aggregates. As supramolecular assembly is very sensitive to sample preparation, multilamellar or multivesicular vesicles are obtained preferentially in vigorously vortexed solutions. Moreover, time-dependent tube formation was observed in gently mixed solutions. Thereby, we could follow the growing mechanism of the unprecedented Y-junctions of supramolecular tubes.

Tandem "One-Shot" Measurement of Residual Chemical Shift Anisotropy and Residual Dipolar Coupling using Biphasic Supramolecular Peptide Liquid Crystals

Both solitary and tandem applications of residual chemical shift anisotropy (RCSA) and residual dipolar coupling (RDC) show great potential for the structural and configurational determination of organic molecules. A critical component of both RDC and RCSA methodologies is the alignment medium, whose availability is limited, especially for RCSA measurement. Moreover, reported RDC and RCSA acquisitions mainly rely on two experiments conducted under two different conditions, which are relatively time-consuming and easily cause experimental errors. Herein, a biphasic supramolecular lyotropic liquid crystalline (LLC) system was developed through the self-assembly of C21H43-CONH-V4K3-CONH2, which could act as an alignment medium for not only RDC but also RCSA extraction in DMSO-d6. Notably, the RCSA extraction was easily achieved via one-shot measurement from a single one-dimensional 13C NMR experiment, with no need for special instruments, devices, and correction. Relying on the biphasic LLC medium, meanwhile, RDC data were simply extracted from a single F1-coupled HSQC experiment, different from the standard protocol that requires two spectral acquisitions corresponding to the isotropic and anisotropic conditions. Collectively, the biphasic LLC medium is applicable for tandem RCSA and RDC measurements in one single sample, advancing the stereochemical elucidation of molecules of interest.

Programming Peptide Liquid Crystal Media to Acquire Independent Sets of Residual Dipolar Couplings and Enantiodiscrimination in Multiple Solvent Systems

Multiple independent sets of residual dipolar couplings (RDCs) acquired by relying on different alignment media show the great potential for de novo structure determination of organic compounds. However, this methodology is severely compromised by the limited availability of multialignment media. In this work, an engineering strategy was developed to program the oligopeptide amphiphiles (OPAs) to create different peptide liquid crystal (LC) media for the acquisition of independent sets of RDCs. With no need for de novo design on peptide sequences, the molecular alignment can be simply modulated by varying the length of the hydrophobic tails within OPAs. Relying on these programmed peptide LC media, five independent sets of RDCs were extracted in a highly efficient and accurate manner. Because of the similar bulk composition of OPAs, this approach offers the significant advantage in circumventing the possible incompatibilities of analytes with one or several different alignment media, therefore avoiding the analysis complication. Notably, these peptide LC media show enantiodifferentiating properties, and the enantiodiscriminating capabilities could also be optimized through the programmed strategy. Furthermore, we show that these media are compatible with different polar solvents, allowing the possible de novo structure elucidation of organic compounds with varied polarities and solubilities.

Weakly aligned Ti3C2Tx MXene liquid crystals: measuring residual dipolar coupling in multiple co-solvent systems

Residual Dipolar Coupling (RDC), acquired relying on weakly alignment media, is highly valuable for the structural elucidation of organic molecules. Arising from the striking features of no background signals and low critical concentrations, two-dimensional (2D) liquid crystals (LCs) show the clear advantages of acting as alignment media to measure RDCs. So far, creating multisolvent compatible 2D LC media through a simple and versatile method is still formidably challenging. Herein, we report the rapid creation of aligned media based on the Ti₃C₂T_x MXene, which self-aligned in multiple co-solvents including CH₃OH-H₂O, DMSO-H₂O, DMF-H₂O, and acetone-H₂O. We demonstrated the applicability of these aligned media for the RDC measurement of small organic molecules with different polarities and solubilities. Notably, Ti₃C₂T_x MXene LCs without chemical modification enabled RDC measurements on aromatic molecules. The straightforward preparation of Ti₃C₂T_x media and its compatibility with multiple solvents will push RDC measurement as a routine methodology for structural elucidation. It may also facilitate the investigation of solvation effects on conformational dynamics.

Advances in hybrid peptide-based self-assembly systems and their applications

Self-assembly of peptides demonstrates a great potential for designing highly ordered, finely tailored supramolecular arrangements enriched with high specificity, improved efficacy and biological activity. Along with natural peptides, hybrid peptide systems composed of natural and chemically diverse unnatural amino acids have been used in various fields, including drug delivery, wound healing, potent inhibition of diseases, and prevention of biomaterial related diseases to name a few. In this review, we provide a brief outline of various methods that have been utilized for obtaining fascinating structures that create an avenue to reproduce a range of functions resulting from these folds. An overview of different self-assembled structures as well as their applications will also be provided. We believe that this review is very relevant to the current scenario and will cover conformations of hybrid peptides and resulting self-assemblies from the late 20^th century through 2022. This review aims to be a comprehensive and reliable account of the hybrid peptide-based self-assembly owing to its enormous influence in understanding and mimicking biological processes.

Programmable alignment media from self-assembled oligopeptide amphiphiles for the measurement of independent sets of residual dipolar couplings in organic solvents

NMR spectroscopy in anisotropic media has emerged as a powerful technique for the structural elucidation of organic molecules. Its application requires weak alignment of analytes by means of suitable alignment media. Although a number of alignment media, that are compatible with organic solvents, have been introduced in the last 20 years, acquiring a number of independent, non-linearly related sets of anisotropic NMR data from the same organic solvent system remains a formidable challenge, which is however crucial for the alignment simulations and deriving dynamic and structural information of organic molecules unambiguously. Herein, we introduce a programmable strategy to construct several distinct peptide-based alignment media by adjusting the amino acid sequence, which allows us to measure independent sets of residual dipolar couplings (RDCs) in a highly efficient and accurate manner. This study opens a new avenue for de novo structure determination of organic compounds without requiring prior structural information.

We report a programmable strategy to construct multi-alignment media via peptide self-assembly for the measurement of independent sets of residual dipolar couplings (RDCs).

Ti3C2Tx MXene Liquid Crystal: Access to Create Background-Free and Easy-Made Alignment Medium

The formation of lyotropic liquid crystals (LCs) in two-dimensional (2D) colloidal dispersions enables the production of mesoscopic/macroscopic ordered materials from nanoscale building blocks. In contrast to graphene oxide (GO) LCs, the practical applications of MXene LCs are less exploited. This study bridges the gap by utilizing a simple and versatile fabrication method to prepare Ti₃C₂T_x MXene LC that can be applied as a background-free alignment medium for the residual dipolar coupling (RDC) measurement of organic molecules. Ti₃C₂T_x LC displays the size- and concentration-dependent alignment degree. Ti₃C₂T_x nanoflakes with an average size of around 600 nm can provide the quadrupolar ²H splitting of 71 Hz at a concentration of 50 mg/mL and show excellent fluidity at such a high concentration. Compared with other alignment media, Ti₃C₂T_x LC exhibits the features of no-background and narrow line broadening, which actualizes the acquirement of clean and high-quality NMR spectra for the accurate RDC extraction. Notably, the alignment of LCs is determined to be maintainable in the redispersed solution after freeze-drying, providing the great convenience for the preparation of alignment Ti₃C₂T_x media, long-term sample preservation, and quantitative evaluation of alignment degree. Meanwhile, the alignment LC media for RDC measurement can be established in other MXenes such as Ti₂CT_x and Ti₃CNT_x. Collectively, our findings demonstrate the potential of creating various alignment media from the fascinating MXene family.

Self-assembly of Helical Polymers and Oligomers to Create Liquid Crystalline Alignment for Anisotropic NMR Parameters

The measurement of anisotropic residual dipolar couplings (RDCs) parameters for the structure elucidation of organic molecules relies on suitable alignment media. Employment of self-assembled liquid crystalline systems to create anisotropic alignment can be an effective way to realize aligned samples and acquire RDCs. This Mini-review highlights the recent advances on amino acid-based helical polymers and supramolecular oligomers forming rigid, rod-like structures that aggregate into ordered liquid crystalline phases, including amino acid-based helical polyisocyanides, polyacetylenes, polypeptides, and oligopeptides assembled alignment media. The methodology for the determination of anisotropic liquid crystals was briefly discussed, and a summary of recent research progress in the enantiodifferentiation of helical polymers aligned media was followed. In addition, the self-assembled mechanism of oligopeptides and their RDCs structural analysis were also described. This article is protected by copyright. All rights reserved.

Solvent-tailored ordered self-assembly of oligopeptide amphiphiles to create an anisotropic meso-matrix

Herein, we have developed a solvent-tailored ordered self-assembly strategy to create anisotropic nanomaterials. A trace amount of water has been found to be a predominant factor to direct peptide self-assembly into an anisotropic meso-matrix in DMSO. The obtained meso-matrix was applied to measure the anisotropic RDC parameter of organic molecules for structural elucidation.