Magnetically driven single DNA nanomotor.

In biological systems, nanoscale molecular motors can generate forces from spontaneous reactions of energy-rich molecules, mostly adenosine triphosphate (ATP), to convert chemical energy into mechanical movement. These motors are roughly 10 nm in size, take steps of a few nanometers, and can exert forces in the piconewton range. [ 1 , 2 ] However, to effi ciently design and construct nanoscale motors in the laboratory, two key requirements must be satisfi ed: 1) the generation of forces suffi cient to power nanomachines or nanodevices and 2) the exertion of precise control over the motion produced. Accomplishing these objectives begins with DNA, which is the ideal building block for nanostructures. In addition, DNA can also be used to create dynamic molecules that replicate machine functions including tweezers, [ 3 ] gears, [ 4 ] walkers, [ 5 ] and motors. [ 6 ] DNA nanomotors, which can be operated with high effi ciency for several cycles, require exergonic reactions, such as hydrolysis of the DNA backbone, [ 5 a, 5 b, 6 c] hydrolysis of ATP, [ 5 c] and DNA hybridization. [ 7 , 8 ] However, operating such DNA nanomotors requires the addition and removal of fuels and waste strands for motor function. This mode of operation is accompanied by the accumulation of waste products, which results in decreased motor effi ciency. Therefore, coupling the nanomotors to clean alternative energy sources would both eliminate the accumulation of waste products and produce a practical high-effi ciency device. Single molecules can be manipulated through magnetic forces by attaching them to magnetic particles and applying an external magnetic fi eld. Using a magnetic fi eld to control the movement of molecules can also avoid molecular damage from photonic fl ux. Therefore, the application of a magnetic fi eld could be of great interest as an alternative energy source for DNA nanomotors and could also satisfy the design requirements enumerated above.