# Controlled Reassociation of Multistranded, Polycrossover DNA Molecules into Double Helices

## TL;DR

This paper shows how DNA nanostructures can change shape in a controlled way, which could be useful for biosensing, drug delivery, and data storage.

## Contribution

A new method for sequence- and temperature-controlled reassociation of complex DNA nanostructures into double helices is introduced.

## Key findings

- PX DNA structures can be reassociated into duplexes using complementary anti-PX structures at specific temperatures.
- Formamide lowers the temperature needed for reassociation, enabling better control.
- The approach works for multiple DNA motifs, showing tunable biostability and nuclease resistance differences.

## Abstract

Shape-changing DNA nanostructures have found applications
in biosensing,
drug delivery, and data storage. Here, we use sequence and temperature-controlled
reassociation of one type of a DNA nanostructure (paranemic crossover
(PX) DNA) into another structure (duplex). In the presence of an anti-PX
structure that is composed of strands that are each complementary
to those in PX DNA, the structures reassociate at specific temperatures
to form duplexes. Using the denaturing agent formamide, we decreased
the temperature required for this reassociation. We demonstrate tunable
biostability, where the structures before and after reassociation
show vastly different nuclease resistance against DNase I. We further
extend the strategy to other polycrossover DNA molecules such as a
double crossover motif and a juxtaposed DNA motif, showing controlled
reassociation of different DNA motifs into duplexes. Our study highlights
the potential for DNA motifs to function as switchable molecular systems,
offering new insights for DNA-based materials and devices.