Structural and morphological diversity of self-assembled synthetic γ-amino acid containing peptides.

Regulating the nanostructural morphology of synthetic hybrid peptides through external stimuli is still a great challenge. Here, we report the synthesis of constrained amino acid building block gabapentin (Gpn) based hybrid peptides and their structural and morphological diversity in different conditions. The synthesized three hybrid peptides Boc-Gpn-Aib-Phe-Aib-OMe (P), Boc-Gpn-Aib-Leu-Aib-OMe (P) and Boc-Gpn-Aib-Tyr-Aib-OMe (P) are folded into C12/C10 hydrogen-bonded double turn conformations. The double turn feature is probed and confirmed by conformational analysis of hybrid peptides using 2D-NMR studies and X-ray crystallography. DMSO-d6 solvent titration investigations also support the double turn conformation adopted by our reported peptides in CDCl3 solution. Solvent assisted self-assembled morphological features of peptides P-P and the salt-prompted mineralization studies of peptide P under ambient conditions are studied. All three reported peptides P-P form diverse supramolecular scaffolds in solid states through non-covalent interactions to attain higher order architectures.

Chemical reactions directed Peptide self-assembly.

Fabrication of self-assembled nanostructures is one of the important aspects in nanoscience and nanotechnology. The study of self-assembled soft materials remains an area of interest due to their potential applications in biomedicine. The versatile properties of soft materials can be tuned using a bottom up approach of small molecules. Peptide based self-assembly has significant impact in biology because of its unique features such as biocompatibility, straight peptide chain and the presence of different side chain functionality. These unique features explore peptides in various self-assembly process. In this review, we briefly introduce chemical reaction-mediated peptide self-assembly. Herein, we have emphasised enzymes, native chemical ligation and photochemical reactions in the exploration of peptide self-assembly.

Mutually Orthogonal Bioconjugation of Vinyl Nucleosides for RNA Metabolic Labeling.

We report a strategy for the orthogonal conjugation of the vinyl nucleosides, 5-vinyluridine (5-VU) and 2-vinyladenosine (2-VA), via selective reactivity with maleimide and tris(2-carboxyethyl)phosphine (TCEP), respectively. The orthogonality was investigated using density functional theory (DFT) and confirmed by reactions with vinyl nucleosides. Further, these chemistries were used to modify RNA for fluorescent cell imaging. These reactions allow for the expanded use of RNA metabolic labeling to study nascent RNA expression within different RNA populations.

Controlling Peptide Self-Assembly through a Native Chemical Ligation/Desulfurization Strategy.

Self-assembled peptides were synthesized by using a native chemical ligation (NCL)/desulfurization strategy that maintained the chemical diversity of the self-assembled peptides. Herein, we employed oxo-ester-mediated NCL reactions to incorporate cysteine, a cysteine-based dipeptide, and a sterically hindered unnatural amino acid (penicillamine) into peptides. Self-assembly of the peptides resulted in the formation of self-supporting gels. Microscopy analysis indicated the formation of helical nanofibers, which were responsible for the formation of gel matrices. The self-assembly of the ligated peptides was governed by covalent and non-covalent interactions, as confirmed by FTIR, CD, fluorescence spectroscopy, and MS (ESI) analyses. Peptide disassembly was induced by desulfurization reactions with tris(2-carboxyethyl)phosphine (TCEP) and glutathione at 80 °C. Desulfurization reactions of the ligated peptides converted the Cys and penicillamine functionalities into Ala and Val moieties, respectively. The self-supporting gels showed significant shear-thinning and thixotropic properties.

In situ generation of redox active peptides driven by selenoester mediated native chemical ligation.

Redox active peptides are generated through selenoester mediated native chemical ligation (NCL). Distinct nanostructures, such as nanotubes to nanofibrillar architectures, were observed for self-assembling soft materials.

Lipase catalyzed inclusion of gastrodigenin for the evolution of blue light emitting peptide nanofibers.

We report lipase catalysed regioselective inclusion of gastrodigenin (p-hydroxybenzyl alcohol: HBA) to a peptide Nmoc-Leu-Trp-OH at physiological pH 7.4. The resultant Nmoc-Leu-Trp-HBA from a reaction cycle of dissipative self-assembly evolves into blue light emitting peptide nanofibers.

Self-programmed nanovesicle to nanofiber transformation of a dipeptide appended bolaamphiphile and its dose dependent cytotoxic behaviour.

Nanostructural transition of a small peptide bolaamphiphile via molecular self-assembly is a challenging task. Here, we report the self-programmed morphological transformation from nanovesicles to nanofibers of a smart peptide bolaamphiphile in its self-assembling hydrogel state. The nanostructural transition occurs based on the structural continuity of the ß-sheet structures. Spectroscopic studies confirmed the different molecular arrangements of the two different nanostructures. Furthermore, the smart bolaamphiphile shows a dose-dependent cytotoxicity and cell-proliferation behaviour.

Peptide-Nanofiber-Supported Palladium Nanoparticles as an Efficient Catalyst for the Removal of N-Terminus Protecting Groups.

Sonication-induced tryptophan- and tyrosine-based peptide bolaamphiphile nanofibers have been used to synthesize and stabilize Pd nanoparticles under physiological conditions. The peptide bolaamphiphile self-assembly process has been thoroughly studied by using several spectroscopic and microscopic techniques. The stiffness of the soft hydrogel matrix was measured by an oscillatory rheological experiment. FTIR and circular dichroism (CD) experiments revealed a hydrogen-bonded ß-sheet conformation of peptide bolaamphiphile molecules in a gel-phase medium. The π-π stacking interactions also played a crucial role in the self-assembly process, which was confirmed by fluorescence spectroscopy. Electron (SEM and TEM) and atomic force microscopy (AFM) studies showed that the peptide bolaamphiphile molecules self-assemble into nanofibrillar structures. Pd nanoparticles were synthesized in the hydrogel matrix in which redox-active tryptophan and tyrosine residues reduce the metal ions to metal nanoparticles. The size of the Pd nanoparticles are in the range of 3-9 nm, and are stabilized by peptide nanofibers. The peptide-nanofiber-supported Pd nanoparticles have shown effective catalytic activity for the removal of N-terminus protecting groups of amino acids and peptides.

Peptide self-assembly driven by oxo-ester mediated native chemical ligation.

We use the oxo-ester mediated native chemical ligation (NCL) reaction to generate a peptide self-assembly process to make supramolecular nanofibers and self-supporting gels.