Metal-Enhanced Helical Chirality of Coil Macromolecules: Bioinspired by Metal Coordination-Induced Protein Folding

Abstract

Although the supramolecular helical structures of biomacromolecules have been studied, the examples of supramolecular systems that are assembled using coils to form helical polymer chains are still limited. Inspired by enhanced helical chirality at the supramolecular level in metal coordination-induced protein folding, a series of alanine-based coil copolymers (poly-(L-co-D)-ala-NH 2 ) carrying (L)-and (D)-alanine pendants were synthesized as a fresh research model to study the cooperative processes between homochirality property and metal coordination. The complexes of poly-(L-co-D)-ala-NH 2 and metal ions underwent a coil-to-helix transition and exhibited remarkable nonlinear effects based on the enantiomeric excess of the monomer unit in the copolymers, affording enhanced helical chirality compared to poly-(L-co-D)-ala-NH 2 . More importantly, the synergistic effect of amplification of asymmetry and metal coordination triggered the formation of a helical molecular orbital on the polymer backbone via the coordination with the d orbital of copper ions. Thus, the helical chirality enhancement degree of poly-(L-co-D)-ala-NH 2 /Cu 2+ complexes (31.4) is approximately 3 times higher than that of poly-(L-co-D)-ala-NH 2 /Ag + complexes (9.8). This study not only provides important mechanistic insights into the enhancement of helical chirality for self-assembly but also establishes a new strategy for studying the homochiral amplification of asymmetry in biological supramolecular systems.

Nonionic Water-Soluble Oligo(ethylene glycol)-Modified Polypeptides with a β-Sheet Conformation

“…Proteins play many important roles in virtually every aspect of living processes, often through their ordered secondary structures such as the α-helix, β-sheet, and turns. − To manipulate the secondary structures and better understand the relationship between the secondary structures and biological functions of proteins, synthetic polypeptides with specific conformations are ideal model systems. − One commonly used method to prepare polypeptides is the ring-opening polymerization (ROP) of amino acid N -carboxylic anhydrides (NCAs). By designing NCAs bearing different side chains and/or through postpolymerization modifications, novel polypeptides with rich functionalities have been created, which often exhibit fascinating material properties and biological functions depending on their distinctive secondary structures. − …”