NYU Scientists Build Nano-Robotic "Arm" Prototype From Synthetic DNA

By introducing a positively charged cobalt compound into the solution surrounding the molecules, the bridge region is converted to an unusual left-handed DNA structure called Z-DNA. Thus, the researchers were able to rotate the arms of the molecule from the initial position into the Z structure. The resulting molecule has the structure diagramed in Figure 2. (Note that the X and Y helices are now on opposite sides of the bridge.) This relative repositioning was detected by means of fluorescent resonance energy transfer spectroscopy, which measures the relative proximity of two dye molecules attached to the free ends of the DX molecule. These are represented by the X and Y dots in the figures. In figure 1, the two dyes are 20 angstroms closer to each other than they are in figure 2, a difference readily detected by this type of measurement. Full size image available through contact

A team of New York University researchers have built a machine from the DNA, the genetic material of all living organisms. Constructed from synthetic DNA molecules, the device has two rigid arms that can be rotated between fixed positions (see Figures 1 and 2). The researchers say that the construction of this device is a first step towards the development of nano-robots that might some day construct individual molecules in molecular-scale factories.

The research team was led by NYU chemistry professor Nadrian C. Seeman. Their findings are reported in the January 14, 1999 issue of Nature. Seeman said, "Using synthetic DNA as a building material, we have constructed a controllable molecular mechanical system. In the short-run, this is an exciting technical achievement. In the long-term, the work will have implications for the development of nano-scale robots and for molecular manufacturing."

The specificity of base-pairing allows strands of DNA to be 'programmed' to self assemble in well-defined ways. Seeman's team took advantage of this fact. The device was constructed by fusing together two synthetic "double-crossover" (DX) DNA molecules. They are joined by a bridge containing the classical right-handed DNA structure called B-DNA. The resulting molecule has the structure diagramed in Figure 1. (Note that the helix with the light dot labeled "X" is on the same side of the bridge as the one with the dark dot labeled "Y.")

These findings are reported in a letter to Nature entitled "A Nanomechanical Device Based on the B-Z Transition of DNA." The authors are as follows: Chengde Mao, Weiqiong Sun, Zhiyon Shen and Nadrian C. Seeman.

Nadrian C. Seeman was born in Chicago in 1945. Following a BS in biochemistry from the University of Chicago, he received his Ph.D. in biological crystallography from the University of Pittsburgh in 1970. His postdoctoral training, at Columbia and MIT, emphasized nucleic acid crystallography. He has received numerous awards for his work on developing ways to construct three-dimensional objects, including cubes and more complex polyhedra, from synthetic DNA molecules. In August, 1998, he reported in Nature that his lab had developed a reliable technique for arranging DNA molecules into two-dimensional crystals.

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Copies of the Nature article are available upon request. To set up an interview with Professor Seeman, contact Josh Plaut at 212-998-6797. Reporters with questions for Nature should contact Lauren Funkhouser at 202-737-2355.

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