The aggregation of Tyr-Phe dipeptide and Val-Tyr-Val tripeptide in aqueous solution and in the presence of SDS and PEO–PPO–PEO triblock copolymer: Fluorescence spectroscopic studies

Elastin-Derived Peptide-Based Hydrogels as a Potential Drug Delivery System

A peptide-based hydrogel sequence was computationally predicted from the Ala-rich cross-linked domains of elastin. Three candidate peptides were subsequently synthesised and characterised as potential drug delivery vehicles. The elastin-derived peptides are Fmoc-FFAAAAKAA-NH2, Fmoc-FFAAAKAA-NH2, and Fmoc-FFAAAKAAA-NH2. All three peptide sequences were able to self-assemble into nanofibers. However, only the first two could form hydrogels, which are preferred as delivery systems compared to solutions. Both of these peptides also exhibited favourable nanofiber lengths of at least 1.86 and 4.57 µm, respectively, which are beneficial for the successful delivery and stability of drugs. The shorter fibre lengths of the third peptide (maximum 0.649 µm) could have inhibited their self-assembly into the three-dimensional networks crucial to hydrogel formation.

A review on recent advances in amino acid and peptide-based fluorescence and its potential applications

Fluorescence is widely used to detect functional groups and ions, and peptides are used in various fields due to their excellent biological activity.

Guiding principles for peptide nanotechnology through directed discovery

Life's diverse molecular functions are largely based on only a small number of highly conserved building blocks - the twenty canonical amino acids. These building blocks are chemically simple, but when they are organized in three-dimensional structures of tremendous complexity, new properties emerge. This review explores recent efforts in the directed discovery of functional nanoscale systems and materials based on these same amino acids, but that are not guided by copying or editing biological systems. The review summarises insights obtained using three complementary approaches of searching the sequence space to explore sequence-structure relationships for assembly, reactivity and complexation, namely: (i) strategic editing of short peptide sequences; (ii) computational approaches to predicting and comparing assembly behaviours; (iii) dynamic peptide libraries that explore the free energy landscape. These approaches give rise to guiding principles on controlling order/disorder, complexation and reactivity by peptide sequence design.

Tunable Pentapeptide Self-Assembled β-Sheet Hydrogels

Oligopeptide‐based supramolecular hydrogels hold promise in a range of applications. The gelation of these systems is hard to control, with minor alterations in the peptide sequence significantly influencing the self‐assembly process. We explored three pentapeptide sequences with different charge distributions and discovered that they formed robust, pH‐responsive hydrogels. By altering the concentration and charge distribution of the peptide sequence, the stiffness of the hydrogels could be tuned across two orders of magnitude (2–200 kPa). Also, through reassembly of the β‐sheet interactions the hydrogels could self‐heal and they demonstrated shear‐thin behavior. Using spectroscopic and cryo‐imaging techniques, we investigated the relationship between peptide sequence and molecular structure, and how these influence the mechanical properties of the hydrogel. These pentapeptide hydrogels with tunable morphology and mechanical properties have promise in tissue engineering, injectable delivery vectors, and 3D printing applications.

The role of amino acid side chains in stabilizing dipeptides: the laser ablation Fourier transform microwave spectrum of Ac-Val-NH2

The steric effects imposed by the isopropyl group of valine in the conformational stabilization of the capped dipeptide N-acetyl-l-valinamide (Ac-Val-NH₂) have been studied by laser ablation molecular beam Fourier transform microwave (LA-MB-FTMW) spectroscopy.

Exploring the sequence space for (tri-)peptide self-assembly to design and discover new hydrogels

Peptides that self-assemble into nanostructures are of tremendous interest for biological, medical, photonic and nanotechnological applications. The enormous sequence space that is available from 20 amino acids probably harbours many interesting candidates, but it is currently not possible to predict supramolecular behaviour from sequence alone. Here, we demonstrate computational tools to screen for the aqueous self-assembly propensity in all of the 8,000 possible tripeptides and evaluate these by comparison with known examples. We applied filters to select for candidates that simultaneously optimize the apparently contradicting requirements of aggregation propensity and hydrophilicity, which resulted in a set of design rules for self-assembling sequences. A number of peptides were subsequently synthesized and characterized, including the first reported tripeptides that are able to form a hydrogel at neutral pH. These tools, which enable the peptide sequence space to be searched for supramolecular properties, enable minimalistic peptide nanotechnology to deliver on its promise.

1,1,1,3,3,3-Hexafluoro-2-propanol and 2,2,2-trifluoroethanol solvents induce self-assembly with different surface morphology in an aromatic dipeptide

Peptide based self-assembled structures, especially those from smaller peptides, have attracted much research interest due to their potential applications as biomaterials. These structures have been produced using different solvents (one of the methods), including alcohols, except fluorinated alcohols, which are believed to support non-aggregated structures. Herein, we have studied the ability of 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) solvents to induce self-assembly of an aromatic dipeptide, namely Tyr-Phe (YF). SEM images showed that HFIP and TFE can induce self-assembly with completely different morphologies, namely microribbons and microspheres, respectively, when YF is dried on a glass surface. Optical microscopic images showed that the microribbons possess birefringence under polarized light, whereas the microspheres do not, indicating that the self-assembled structures derived from HFIP solution are more highly ordered and crystalline in nature than those derived from TFE. Spectroscopic results indicated that the YF peptide adopts completely different conformations in these solvents. Time-dependent experiments suggested that the conformation of YF in HFIP is kinetically unstable and undergoes conformational change, whereas it is more stable in TFE, demonstrating that the modes of interaction of the TFE and HFIP solvents with the peptide are dissimilar. Different self-assembled structures were observed at different time intervals when YF was incubated in neat HFIP and 10% HFIP-90% TFE, establishing that the monomeric conformation plays a dominant role in deciding the final self-assembled structure (morphology) of YF. The current results demonstrate that TFE and HFIP solvents can produce self-assembled structures with different morphologies during solvent evaporation, despite their similar properties, such as secondary structural (α-helix) induction and preserving the peptide in its monomeric conformation in solution.

Interaction between graphene oxide and Pluronic F127 at the air-water interface

Triblock copolymer Pluronic F127 (PF127) has previously been demonstrated to disperse graphene oxide (GO) in electrolyte solution and block the hydrophobic interaction between GO and l-tryptophan and l-tyrosine. However, the nature of this interaction between PF127 and GO remains to be characterized and elucidated. In the present study, we aimed to characterize and understand the interaction between GO and PF127 using a 2-dimensional Langmuir monolayer methodology at the air-water interface by surface pressure-area isotherm measurement, stability, adsorption, and atomic force microscopy (AFM) imaging. Based on the observation of surface pressure-area isotherms, adsorption, and stability of PF127 and PF127/GO mixture at the air-water interface, GO is suggested to change the conformation of PF127 at the air-water interface and also drag PF127 from the interface to the bulk subphase. Atomic force microscopy (AFM) image supports this assumption, as GO and PF127 can be observed by spreading the subphase solution outside the compressing barriers, as shown in the TOC graphic.

Solution behavior of normal and reverse triblock copolymers (pluronic L44 and 10R5) individually and in binary mixture

Solution properties of pluronics L44 or L [(PEO)(10)(PPO)(23)(PEO)(10)] and 10R5 or R [(PPO)(8)(PEO)(22)(PPO)(8)] were studied individually as well in their binary mixtures in aqueous medium. The critical micelle concentration (CMC), critical micelle temperature, and cloud point (CP) were determined. Ideal and nonideal behaviors of their mixtures in the formation of CMC and CP were observed; the energetics of the studied processes were determined. Spectrophotometry, isothermal titration calorimetry and dynamic light scattering (DLS) methods were used for evaluations. Morphologies of the dispersed L, R, and their mixtures along with their polydispersities were determined from DLS measurements. Atomic force microscopy was also employed. The interfacial properties of L and R were investigated forming Langmuir monolayers in a surface balance. The surface pressures (π) generated by the compounds were moderate, the area per molecule was higher for R than L. R has shown antibacterial activity against both gram positive and gram negative bacteria whereas L was inactive in this respect.