Effect of Ionic Strength on the Thermal Stability of DNA Origami Nanostructures

The stability of DNA origami nanostructures in aqueous media is closely tied to the presence of cations that screen electrostatic inter-helix repulsion. Here, the thermal melting behavior of different DNA origami nanostructures is investigated in dependence on Mg2+ concentration and compared to calculated ensemble melting temperatures of the staple strands used in DNA origami folding. Strong deviations of the measured DNA origami melting temperatures from the calculated ones are observed, in particular at high ionic strength where the melting temperature saturates and becomes independent of ionic strength. The degree of deviation between the measured and calculated melting temperatures further depends on the superstructure and in particular the mechanical properties of the DNA origami nanostructures. This indicates that thermal stability of a given DNA origami design at high ionic strength is governed predominantly not by electrostatic inter-helix repulsion but mostly by mechanical strain.

Automated summary

The stability of DNA origami nanostructures in aqueous media is affected by the presence of cations, which can screen electrostatic inter-helix repulsion. This study examines the thermal melting behavior of different DNA origami nanostructures under varying concentrations of Mg2+ and compares it to the calculated ensemble melting temperatures of the staple strands used in DNA origami folding. The results show significant deviations between the measured and calculated melting temperatures, particularly at high ionic strength where the melting temperature saturates and becomes independent of ionic strength. The degree of deviation also depends on the superstructure and mechanical properties of the DNA origami nanostructures, suggesting that mechanical strain plays a more dominant role in thermal stability at high ionic strength.