Intramolecular Interactions of Conjugated Polymers Mimic Molecular Chaperones to Stabilize Protein-Polymer Conjugates

The power and elegance of protein-polymer conjugates has solved many vexing problems for society. Rational design of these complex covalent hybrids depends on a deep understanding of how polymer physicochemical properties impact the conjugate structure-function-dynamic relationships. We have generated a large family of chymotrypsin-polymer conjugates which differ in polymer length and charge, using grafting-from atom-transfer radical polymerization, to elucidate how the polymers influenced enzyme structure and function at pHs that would unfold and inactivate the enzyme. We also used molecular dynamics simulations to deepen our understanding of protein-polymer intramolecular interactions. Remarkably, the data revealed that, contrary to current thoughts on how polymers stabilize proteins, appropriately designed polymers actually stabilize partially unfolded intermediates and assist in refolding to an active conformation. Long, hydrophilic polymers minimized interfacial interactions in partially unfolded conjugates leading to increased stabilization. The design of covalently attached intramolecular biomimetic chaperones that drive protein refolding could have far reaching consequences.