Folding Cooperativity of Synthetic Polypeptides with or without “Tertiary” Interactions

Model-based studies on helix–coil transition and folding cooperativity of synthetic polypeptides have contributed to the understanding of protein folding and stability and to the development of polypeptide-based functional materials. Polypeptide-containing macromolecules with complex architectures, however, remain a challenge in the model-based analysis. Herein, a modified Schellman–Zimm–Bragg model has been utilized to quantitatively analyze the folding cooperativity of polypeptide-containing macromolecules. While the helix–coil transition of homopolypeptides (e.g., poly(e-benzyloxycarbonyl-l-lysine) (PZLL)) can be described by the classic model, the folding of grafted polypeptide chains in the comb macromolecules (e.g., polynorbornene-g-poly(e-benzyloxycarbonyl-l-lysine) (PN-g-PZLL)) cannot be accurately predicted by the existing theories, due to the side-chain interactions between grafted polypeptides in the comb macromolecules. Incorporating nonlocal interaction explicability into the statistical mech...