Conformation Controlled Hydrogelation of Minimalistic α, γ Hybrid Peptide.

A majority of short peptide (≤7 amino acids) hydrogels are primarily assembled via cross ß-structure formation. In contrast to the natural trend, herein, we report the formation of supramolecular hydrogel from the ultrashort hybrid folded peptide composed of canonical α-amino acid and noncanonical γ-amino acid, Fmoc-γPhe-Phe-OH. The designed hybrid peptide hydrogel is composed of entangled fibers, has viscoelastic properties, exhibits proteolytic stability, and exhibits cytocompatibility with L929 fibroblast cells. Mutating the peptide sequence by altering the position of γPhe from the N-termini to C-termini transforms the self-assembly into crystalline aggregates. Combining FTIR, 2D NMR, and DFT calculations revealed that the hydrogel-forming peptide adopts a C9 H-bonded conformation, resembling the well-known γ-turn. However, the isomeric hybrid peptide adopts an extended structure. The present study highlights the importance of secondary structure in the higher order assembly of minimalist hybrid peptides and broadens the range of secondary structures to design short peptide-based hydrogels.

Peptide hydrogen-bonded organic frameworks.

Hydrogen-bonded porous frameworks (HPFs) are versatile porous crystalline frameworks with diverse applications. However, designing chiral assemblies or biocompatible materials poses significant challenges. Peptide-based hydrogen-bonded porous frameworks (P-HPFs) are an exciting alternative to conventional HPFs due to their intrinsic chirality, tunability, biocompatibility, and structural diversity. Flexible, ultra-short peptide-based P-HPFs (composed of 3 or fewer amino acids) exhibit adaptable porous topologies that can accommodate a variety of guest molecules and capture hazardous greenhouse gases. Longer, folded peptides present challenges and opportunities in designing P-HPFs. This review highlights recent developments in P-HPFs using ultra-short peptides, folded peptides, and foldamers, showcasing their utility for gas storage, chiral recognition, chiral separation, and medical applications. It also addresses design challenges and future directions in the field.

Exploring Helical Peptides and Foldamers for the Design of Metal Helix Frameworks: Current Trends and Future Perspectives.

Flexible and biocompatible metal peptide frameworks (MPFs) derived from short and ultra-short peptides have been explored for the storage of greenhouse gases, molecular recognition, and chiral transformations. In addition to short flexible peptides, peptides with specifically folded conformations have recently been utilized to fabricate a variety of metal helix frameworks (MHFs). The secondary structures of the peptides govern the structure-assembly relationship and thereby control the formation of three-dimensional (3D)-MHFs. Particularly, the hierarchical structural organization of peptide-based MHFs has not yet been discussed in detail. Here, we describe the recent progress of metal-driven folded peptide assembly to construct 3D porous structures for use in future energy storage, chiral recognition, and biomedical applications, which could be envisioned as an alternative to the conventional metal-organic frameworks (MOFs).