Department of Chemistry & Institute
of Materials Science, University of Connecticut
In the 1950s, Doty and co-workers found that a polypeptide chain can reversibly convert between the helical and coiled form in solution. The theories of helix-coil transition were then proposed by Schellman, Zimm, Gibbs, Lifson and others, and developed into one of the most fruitful subjects in macromolecular science. Doty also discovered at that time, in the synthesis of polypeptides, the addition of monomer to the helical form may occur a few times faster than that to the coiled form. A helical chain growth mechanism was proposed by Doty to explain the structured-based acceleration found in the kinetics of polymerization. However, the implication of this mechanism is not as extensively exploited as that of the helix-coil transition. Interestingly, the primary mechanism underlying the helical chain growth of polypeptides shares a remarkable similarity with that of helix-coil transition: both are a nucleation-controlled two-stage process, and a cooperativity factor can be defined to describe the sharp contrast between the two stages. Herein, we present some of our latest results arising from revisiting the helix-coil transition and the helical chain growth behaviors in synthetic polypeptides. We have focused on the applicability of these models in describing the experimental model systems under the limiting cases, such as the polypeptides of high molecular weights, or the polypeptides with local crowding owning to the macromolecular architectures. The aim is to integrate theoretical and experimental approaches to allow for model-driven engineering of complex, polypeptide-based systems in the future.