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  1. This study revisits the material properties of solid “liquid crystalline” films made from synthetic helical polypeptides and explores their structure–property relationships. Poly(γ-benzyl-l-glutamate) (PBLG) with various molecular weights and architectures (linear, comb-, and brush-like) were transformed into films through mechanical hot pressing. The resulting materials are composed of helical PBLGs arranged in a near-hexagonal lattice, similar to those formed by casting from a concentrated solution in 1,2-dichloroethane (EDC). Despite exhibiting lower apparent crystallinity, these films showed superior mechanical strength, potentially due to the promotion of more interrupted helices and their entanglements under high temperature and pressure. A pronounced chain length effect on the tensile modulus and mechanical strength was observed, aligning with the “interrupted helices” model proposed by us and others. Macromolecules with a polynorbornene (PN) backbone and PBLG side chains mirrored the mechanical and viscoelastic properties of linear PBLGs. Our findings suggest that the folding structures of polypeptide chains and the discontinuity of the folding in longer chains are more influential in determining the macroscopic mechanical properties of the resultant materials than crystallinity, packing ordering, or macromolecular architecture, emphasizing the critical role of cohesive chain network formation in achieving enhanced mechanical strength. This research also presents a versatile approach to fabricating solid-state polypeptide materials, circumventing solubility challenges associated with traditional solution-based processing methods. 
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    Free, publicly-accessible full text available March 12, 2025
  2. The biological significance of self-assembled protein filament networks and their unique mechanical properties have sparked interest in the development of synthetic filament networks that mimic these attributes. Building on the recent advancement of autoaccelerated ring-opening polymerization of amino acid N-carboxyanhydrides (NCAs), this study strategically explores a series of random copolymers comprising multiple amino acids, aiming to elucidate the core principles governing gelation pathways of these purpose-designed copolypeptides. Utilizing glutamate (Glu) as the primary component of copolypeptides, two targeted pathways were pursued: first, achieving a fast fibrillation rate with lower interaction potential using serine (Ser) as a comonomer, facilitating the creation of homogeneous fibril networks; and second, creating more rigid networks of fibril clusters by incorporating alanine (Ala) and valine (Val) as comonomers. The selection of amino acids played a pivotal role in steering both the morphology of fibril superstructures and their assembly kinetics, subsequently determining their potential to form sample-spanning networks. Importantly, the viscoelastic properties of the resulting supramolecular hydrogels can be tailored according to the specific copolypeptide composition through modulations in filament densities and lengths. The findings enhance our understanding of directed self-assembly in high molecular weight synthetic copolypeptides, offering valuable insights for the development of synthetic fibrous networks and biomimetic supramolecular materials with custom-designed properties. 
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    Free, publicly-accessible full text available March 6, 2025
  3. null (Ed.)
    With PEG-like properties, such as hydrophilicity and stealth effect against protein absorption, oligo(ethylene glycol) (OEG)-functionalized polypeptides have emerged as a new class of biomaterials alternative to PEG with polypeptide-like properties. Synthesis of this class of materials, however, has been demonstrated very challenging, as the synthesis and purification of OEG-functionalized N -carboxyanhydrides (OEG-NCAs) in high purity, which is critical for the success in polymerization, is tedious and often results in low yield. OEG-functionalized polypeptides are therefore only accessible to a few limited labs with expertise in this specialized NCA chemistry and materials. Here, we report the controlled synthesis of OEG-functionalized polypeptides in high yield directly from the OEG-functionalized amino acids via easy and reproducible polymerization of non-purified OEG-NCAs. The prepared amphiphilic block copolypeptides can self-assemble into narrowly dispersed nanoparticles in water, which show properties suitable for drug delivery applications. 
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  4. null (Ed.)
  5. Abstract

    The recent advances in accelerated polymerization ofN-carboxyanhydrides (NCAs) enriched the toolbox to prepare well-defined polypeptide materials. Herein we report the use of crown ether (CE) to catalyze the polymerization of NCA initiated by conventional primary amine initiators in solvents with low polarity and low hydrogen-bonding ability. The cyclic structure of the CE played a crucial role in the catalysis, with 18-crown-6 enabling the fastest polymerization kinetics. The fast polymerization kinetics outpaced common side reactions, enabling the preparation of well-defined polypeptides using an α-helical macroinitiator. Experimental results as well as the simulation methods suggested that CE changed the binding geometry between NCA and propagating amino chain-end, which promoted the molecular interactions and lowered the activation energy for ring-opening reactions of NCAs. This work not only provides an efficient strategy to prepare well-defined polypeptides with functionalized C-termini, but also guides the design of catalysts for NCA polymerization.

     
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  6. Ribozymes synthesize proteins in a highly regulated local environment to minimize side reactions caused by various competing species. In contrast, it is challenging to prepare synthetic polypeptides from the polymerization of N -carboxyanhydrides (NCAs) in the presence of water and impurities, which induce monomer degradations and chain terminations, respectively. Inspired by natural protein synthesis, we herein report the preparation of well-defined polypeptides in the presence of competing species, by using a water/dichloromethane biphasic system with macroinitiators anchored at the interface. The impurities are extracted into the aqueous phase in situ, and the localized macroinitiators allow for NCA polymerization at a rate which outpaces water-induced side reactions. Our polymerization strategy streamlines the process from amino acids toward high molecular weight polypeptides with low dispersity by circumventing the tedious NCA purification and the demands for air-free conditions, enabling low-cost, large-scale production of polypeptides that has potential to change the paradigm of polypeptide-based biomaterials. 
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