Forced Unfolding of Protein-Inspired Single-Chain Random Heteropolymers

Synthetic random heteropolymers (RHPs) with high chemical heterogeneity can self-assemble into single-chain nanoparticles that exhibit features reminiscent of natural proteins, such as topological polymorphism. Using all-atom molecular dynamics simulations, this work investigates the structure and single-chain mechanical unfolding of a library of four-component RHPs in water, studying the effects of sequence, composition, configuration, and molecular weight. Results show that compactified RHPs can have highly dynamic unfolding behaviors which are dominated by complex side-chain interactions and prove markedly different from their homopolymer counterparts. For a given sequence and conformation, an RHP’s backbone topology can strongly impact its unfolding response, hinting at the importance of topological design in the nanoscale mechanics of heteropolymers. In addition, we identify enthalpically-driven reconfiguration upon unfolding, observing a solvent-shielding protection mechanism similar to protein stabilization by PEGylation. This work provides the first computational evidence for the force-induced unfolding of protein-inspired multicomponent heteropolymers.