We present a study of the hybridization of complementary DNA hairpin loops, with particular reference to their use as fuel for autonomous DNA devices. The rate of spontaneous hybridization between complementary hairpins can be reduced by increasing the neck length or decreasing the loop length. Hairpins with larger loops rapidly form long-lived kissed complexes. Hairpin loops may be opened by strand displacement using an opening strand that contains the same sequence as half of the neck and a "toehold" complementary to a single-stranded domain adjacent to the neck. We find loop opening via an external toehold to be 10-100 times faster than via an internal toehold. We measure rates of loop opening by opening strands that are at least 1000 times faster than the spontaneous interaction between hairpins. We discuss suitable choices for loop, neck, and toehold length for hairpin loops to be used as fuel for autonomous DNA devices.

Metastable two-stranded DNA loops can be assembled into extended DNA oligomers by kinetically controlled self-assembly. Along the designed reaction pathway, the sequence of hybridization reactions is controlled by progressively revealing toeholds required to initiate strand-displacement reactions. The product length depends inversely on seed concentration and ranges from a few hundred to several thousand base-pairs.

Continuous rotation of DNA around its phosphate backbone is achieved with a simple nanomotor, which is driven by an electric field oscillated between four orientations (see image). The motor consists of a DNA rotor and a partially single‐stranded DNA axle held between a surface and a magnetic bead. Rotation is caused by realignment of the rotor DNA with the oscillated electric field.

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Ziehen und Strecken: Aus DNA wurde eine molekulare Maschine konstruiert, bei der durch das Zusammenwirken vieler molekularer Pinzetteneinheiten eine Bewegung über größere Distanzen erreicht wird. Diese Maschine ist dazu in der Lage, sich wiederholt auf 75 % ihrer vollständig gestreckten Form zusammenzuziehen (siehe Bild). Angetrieben wird diese Bewegung durch zwei „Treibstoff“‐Stränge.