Morphology Diversity of L‐Phenylalanine‐Based Short Peptide Supramolecular Aggregates and Hydrogels

Supramolecular aggregates and hydrogels of diverse morphologies can be obtained by replacing the widely studied aromatic N‐capping of phenylalanine derivatives by long alkyl chains. Simple changes in chain length and number of phenylalanine residues lead to a diversity of nanostructures including networks of fibers of different handedness and flat nanosheets. Moreover, additional morphologies could be achieved by a simple pathway selection. These results evidence the impact that small structural and methodological changes have on the self‐assembly of small peptide fragments and recall its relevance for the understanding of protein aggregation as well as for the fine control of peptide material properties for applications

A supramolecular hydrogel as a reusable heterogeneous catalyst for the direct aldol reaction

An L-proline based supramolecular hydrogel is used as an efficient heterogeneous organocatalyst for the direct aldol reaction with high stereoselectivity (up to 90% ee) and recyclability (up to 3 runs). The reversible nature of this self-assembled supramolecular system allows for easy recovery and regeneration of the catalys

Remarkable increase in basicity associated with supramolecular gelation

L-Proline derivatives which are able to form supramolecular gels show an amazing basicity increase in the aggregated (gel) state as compared to solution. As a result they behave as enantioselective catalysts for the aldol reaction in solution but produce a base-catalyzed aldol racemisation in the gel stat

Molecular recognition through divalent interactions with a self-assembled fibrillar network of a supramolecular organogel

The interaction of phenol derivatives with the self-assembled fibrillar network of two different supramolecular gels has been studied. NMR relaxometry reveals the selective interaction of resorcinol over other related molecules with a gel formed by the gelator 2 which contains terminal pyridine units. No selectivity is observed for a related gelator that contains phenyl instead of pyridine moieties. The selectivity observed by NMR experiments permits the selective suppression of the 1H NMR signals of resorcinol. This behaviour is translated to macroscopic properties such as the thermal stability of the gels. The observed selectivity together with X-ray diffraction data and molecular modelling suggest that the gels formed by 2 present arrays of pyridine H-bond acceptor groups capable of selective multivalent interaction with phenolic substrate

Supramolecular gel formation and self-correction induced by aggregation-driven conformational changes

The formation of self-assembled fibrillar networks by low molecular weight peptidomimetics containing a Pro-Val moiety is reported; insight into the aggregation mechanism is provided revealing that it is associated to an unfolding process and that a fibrillar network formed under kinetic control can self-correct into a thermodynamically stable on

Effect of Hyaluronic Acid on the Self-Assembly of a Dipeptide-Based Supramolecular Gel

The combination of polymers and low molecular weight (LMW) compounds is a powerful approach to prepare new supramolecular materials. Here we prepare two-component hydrogels made by a well-known and biologically active polymer, hyaluronic acid (HA), and a dipeptide-based supramolecular gelator. We undertake a detailed study of materials with different compositions including macroscopic (hydrogel formation, rheology) and micro/nanoscopic characterization (electron microscopy, X-ray powder diffraction). We observe that the two components mutually benefit in the new materials: a minimum amount of HA helps to reduce the polymorphism of the LMW network leading to reproducible hydrogels with improved mechanical properties; the LMW component network holds HA without the need for an irreversible covalent crosslinking. These materials have a great potential for biomedical application as, for instance, extracellular matrix mimetics for cell growth. As a proof of concept, we have observed that this material is effective for cell growth in suspension and avoids cell sedimentation even in the presence of competing cell-adhesive surfaces. This may be of interest to advanced cell delivery techniques.Funding for open access charge: CRUE-Universitat Jaume

Mechanistic Insight into the Lability of the Benzyloxycarbonyl (Z) Group inN-Protected Peptides under Mild Basic Conditions

The unexpected lability of Z protecting group under mild basic conditions at room temperature is explained by a mechanism based on anchimeric assistance. It is found that the vicinal amide group stabilizes the tetrahedral intermediate formed after the nucleophilic addition of hydroxide to the carbonyl of the Z group. This effect operates in N-protected tripeptides and tetrapeptides but Z-protected dipeptides are stable under the same conditions due to the blockage of the vicinal amide NH by intramolecular H-bonding with terminal carboxylate moiety

Insight into the esterase like activity demonstrated by an imidazole appended self-assembling hydrogelator

A low molecular weight hydrogelator with a covalently appended imidazole moiety is reported. Capable of percolating water in the pH range of 6 to 8, it proves to be an efficient catalyst upon self-assembly, showing Michaelis-Menten type kinetics. Activities at different pH values correlated with dramatic structural changes were observed. It can hydrolyse p-nitrophenyl acetate (pNPA) as well as inactivated esters, and l and d-phenylalanine methyl esters. The enhanced activity can be related to the conglomeration of catalytic groups upon aggregation resulting in their close proximity and the formation of hydrophobic pockets

Selective and highly efficient dye scavenging by a pH-responsive molecular hydrogelator

A structurally simple low molecular weight hydrogelator derived from isophthalic acid forms robust pH-responsive hydrogels capable of highly efficient and selective dye adsorption

Transcription of Nanofibrous Cerium Phosphate Using a pH-Sensitive Lipodipeptide Hydrogel Template

A novel and simple transcription strategy has been designed for the template-synthesis of CePO4 xH2O nanofibers having an improved nanofibrous morphology using a pH-sensitive nanofibrous hydrogel (glycine-alanine lipodipeptide) as structure-directing scaffold. The phosphorylated hydrogel was employed as a template to direct the mineralization of high aspect ratio nanofibrous cerium phosphate, which in-situ formed by diffusion of aqueous CeCl3 and subsequent drying (60 C) and annealing treatments (250, 600 and 900 C). Dried xerogels and annealed CePO4 powders were characterized by conventional thermal and thermogravimetric analysis (DTA/TG), and Wide-Angle X-ray powder diffraction (WAXD) and X-ray powder diffraction (XRD) techniques. A molecular packing model for the formation of the fibrous xerogel template was proposed, in accordance with results from Fourier-Transformed Infrarred (FTIR) and WAXD measurements. The morphology, crystalline structure and composition of CePO4 nanofibers were characterized by electron microscopy techniques (Field-Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy/High-Resolution Transmission Electron Microscopy (TEM/HRTEM), and Scanning Transmission Electron Microscopy working in High Angle Annular Dark-Field (STEM-HAADF)) with associated X-ray energy-dispersive detector (EDS) and Scanning Transmission Electron Microscopy-Electron Energy Loss (STEM-EELS) spectroscopies. Noteworthy, this templating approach successfully led to the formation of CePO4 H2O nanofibrous bundles of rather co-aligned and elongated nanofibers (10–20 nm thick and up to ca. 1 m long). The formed nanofibers consisted of hexagonal (P6222) CePO4 nanocrystals (at 60 and 250 C), with a better-grown and more homogeneous fibrous morphology with respect to a reference CePO4 prepared under similar (non-templated) conditions, and transformed into nanofibrous monoclinic monazite (P21/n) around 600 C. The nanofibrous morphology was highly preserved after annealing at 900 C under N2, although collapsed under air conditions. The nanofibrous CePO4 (as-prepared hexagonal and 900 C-annealed monoclinic) exhibited an enhanced UV photo-luminescent emission with respect to non-fibrous homologues