Out of Equilibrium Coil-Helix Transition Driven by Chemical Fuels

The coil-helix transition of biopolymers is an important secondary structure reconstruction and plays crucial role in biological events. It is known that under thermodynamic equilibrium, the coil-helix transition of polypeptides can be well controlled by external stimulus. In the current study, we are able to manipulate the conformation of PLG to transfer between α-helix and random coil conformation utilizing contiuns supply of the chemical energy flow, which is away from chemical equilibrium. We found that in the presence of EDC/NHS, carboxylate with negative charge on PLG side chains will be firstly activated by EDC and then converted into their corresponding electroneutral NHS-esters, followed by hydrolysis to form carboxylate and NHS again. Using this reaction cycle, we are able to control the charge interaction between side chains of PLG and switch the system from random coil conformation with low free energy to α-helical structure with high free energy in the presence of chemical fuel. Moreover, the lifetime and content of the transient α-helices can be tuned by adjusting the amount of chemical fuels and nucleophile. The fuel-mediated coil-helix transition of polypeptides presented here may provide an efficient strategy for mimicry the behavior of dynamic proteins found in natural systems and bring intriguing opportunities for future adaptive materials.