Polynucleic acid nanomechanical device controlled by hybridization topology

A polynucleic acid nanomechanical device capable of cycling between two topoisomeric states upon the sequential addition of fuel and set strands of nucleic acids, comprising a nucleic acid paranemic crossover molecule having a four-stranded coaxial structure of flanking parallel Watson-Crick double helices of nucleic acid strands with two backbones, two pairs of ends, a plurality of major and minor grooves, a central dyad axis, and reciprocal crossovers, where two strands of a strand pair from one helix pass over to the other helix and which reciprocal crossovers flank the central dyad axis at every major and minor groove separation where two strands of a strand pair from one helix approach the central dyad axis, each of said strands being involved in a crossover at the start and end of a Watson-Crick helical turn, wherein:

• the device is cycled between said nucleic acid paranemic crossover molecule and its JX2 topoisomer, said JX2 topoisomer differing from said nucleic acid paranemic crossover molecule by having one pair of ends rotated relative to the other pair of ends by 180° and by having two adjacent sites where said two backbones juxtapose without the strands being involved in a crossover;
• and
• a segment of a strand from each of said strand pairs of said nucleic acid paranemic crossover molecule, which segment is referred to as a PX set strand and which is broken from the rest of the strand, is stripped from said nucleic acid paranemic crossover molecule by the addition of fuel strands complementary to said PX set strands followed by the addition of JX2 set strands to convert said nucleic acid paranemic crossover molecule to its JX2 topoisomer, said JX2 topoisomer being converted/cycled back to said nucleic acid paranemic crossover molecule by the addition of fuel strands complementary to said JX2 set strands to strip said JX2 set strands from said JX2 topoisomer followed by the addition of PX set strands.