Abstract
The ultrasensitive threshold response is ubiquitous in biochemical systems. In contrast, achieving ultrasensitivity in synthetic molecular structures in a controllable way is challenging. Here, we propose a chemomechanical approach inspired by Michell’s instability to realize it. A sudden reconfiguration of topologically constrained rings results when the torsional stress inside reaches a critical value. We use DNA origami to construct molecular rings and then DNA intercalators to induce torsional stress. Michell’s instability is achieved successfully when the critical concentration of intercalators is applied. Both the critical point and sensitivity of this ultrasensitive threshold reconfiguration can be controlled by rationally designing the cross-sectional shape and mechanical properties of DNA rings.
Highlights
The ultrasensitive threshold response is ubiquitous in biochemical systems
As shown in the result of finite element (FE) analysis for the ring (Fig. 1b and Supplementary Note 1), the applied twist is stored purely as torsional strain energy in the structure, resulting in zero writhe (Wr) and a constant in-plane bending strain energy. When it exceeds θcr, the ring structure suddenly becomes supercoiled with a nonzero writhe due to Michell’s instability, where the stored torsional strain energy is drastically transformed into the out-of-plane bending energy
Rings are capable of buffering a certain amount of torsional strain energy, enabling a switch-like, threshold reconfiguration from a circle to a supercoil under varied twist angles
Summary
The ultrasensitive threshold response is ubiquitous in biochemical systems. In contrast, achieving ultrasensitivity in synthetic molecular structures in a controllable way is challenging. We are able to control the critical point and the sensitivity of this ultrasensitive threshold reconfiguration by rationally designing the cross-sectional shape and the mechanical properties of DNA rings. To investigate Michell’s instability at the molecular level, we constructed ring structures using the DNA origami method[20,21,22] (Fig. 1c).
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