Catalysis observed in enzymatic processes and protein polymerizations often relies on the use of supramolecular interactions and the organization of functional elements in order to gain control over the spatial and temporal elements of fundamental cellular processes. Harnessing these cooperative interactions to catalyse reactions in synthetic systems, however, remains challenging due to the difficulty in creating structurally controlled macromolecules. Here, we report a polypeptide-based macromolecule with spatially organized α-helices that can catalyse its own formation. The system consists of a linear polymeric scaffold containing a high density of initiating groups from which polypeptides are grown, forming a brush polymer. The folding of polypeptide side chains into α-helices dramatically enhances the polymerization rate due to cooperative interactions of macrodipoles between neighbouring α-helices. The parameters that affect the rate are elucidated by a two-stage kinetic model using principles from nucleation-controlled protein polymerizations; the key difference being the irreversible nature of this polymerization.

All polymerizations were conducted in a water/DCM biphasic system in the presence of PEG−PBLG macroinitiators. [I] 0 = 0.5 mM except for the last three entries. ELG, γ-ethyl-L -glutamate; ZLL, e-carboxybenzyl-L -lysine. † Polymerization time reaching 98% monomer conversion. ‡ Obtained MW (designed MW*). § Synthesis of block copolymer through sequential monomer addition. [I] 0 = 1.0, 0.5, and 0.25 mM for the first, second, and third block, respectively. Song et al.

This review provides an overview of smart chemistry developed and utilized in the last 5-10 years in polymer-based drug delivery nanomedicine. Smart chemistry not only facilitates the controlled drug loading in a highly specific manner, but also potentially controls the drug release kinetics at the targeted tissues. This review highlights the emergence of new chemistry or unique utilization of conventional chemistry in drug delivery, which is believed to play an important role in developing next generation nanomedicine.

Enzymes provide optimal three-dimensional structures for substrate binding and the subsequent accelerated reaction. Such folding-dependent catalytic behaviors, however, are seldom mechanistically explored with reduced structural complexity. Here, we demonstrate that the α-helix, a much simpler structural motif of enzyme, can facilitate its own growth through the self-catalyzed polymerization of N-carboxyanhydride (NCA) in dichloromethane. The reversible binding between the N terminus of α-helical polypeptides and NCAs promotes rate acceleration of the subsequent ring-opening reaction. A two-stage, Michaelis–Menten-type kinetic model is proposed by considering the binding and reaction between the propagating helical chains and the monomers, and is successfully utilized to predict the molecular weights and molecular-weight distributions of the resulting polymers. This work elucidates the mechanism of helix-induced, enzyme-mimetic catalysis, emphasizes the importance of solvent choice in the discovery of new reaction type, and provides a route for rapid production of well-defined synthetic polypeptides by taking advantage of self-accelerated ring-opening polymerizations.

Cooperative interactions and transitions are among the most important strategies utilized by biological systems to regulate a variety of physical and chemical processes. We report herein an auto-accelerated, rapid cooperative polymerization of N-carboxyanhydrides (NCAs) with initiators structurally as simple as linear aliphatic diamines for the synthesis of polypeptides. The polymerization initiated by diamines proceeds via the formation of "hinged" polypeptides, which are two blocks of helical chains connected head-to-head by the diamine molecules in the polymerization solution. The reactions follow a two-stage, cooperative polymerization kinetic; the cooperative interactions between the macrodipoles of the two hinged helical polypeptides dramatically accelerate the polymerization. Compared to the NCA polymerization initiated by the hexylamine (CH 3 (CH 2 ) 5 NH 2 ), the chain propagation rate of the NCA polymerization is increased by more than 600 times when initiated by its diamine analogue (1,6-diaminohexane, NH 2 (CH 2 ) 6 NH 2 ). This proximity-induced cooperative polymerization showcases the single helix as a remarkable cooperativityenabling motif in synthetic chemistry.