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In previous DNA nanotechnology efforts, duplex DNA has been used as a static lattice to construct geometrical objects in three dimensions. Instead of manipulating DNA alone into such shapes, the researchers are using DNA to control the folding and resulting structure of RNA. Eventually, they envision building supramolecular machines whose inner workings are governed by twisted strands of DNA.

In a paper that has been accepted for publication in the Journal of the American Chemical Society, and posted on its Web site, Silverman and graduate student Chandrasekhar Miduturu begin with a piece of unfolded RNA. Through specific chemical reactions, they attach two strands of DNA, each resembling one side of a ladder. The two DNA strands spontaneously bind together, then the researchers add magnesium ions to initiate folding of the RNA.

"Folding of the RNA structure competes with formation of the DNA constraint until a chemical balance is reached," Silverman said. "In some cases, the DNA is like a barnacle, just stuck onto the RNA without perturbing its structure. In other cases, the DNA changes the RNA structure. We can predict which situation will occur based on the shape of the RNA and on the attachment points of the DNA constraint."

In cases where the normal RNA shape and the DNA constraint cannot co-exist simultaneously, the balance between competing RNA and DNA structures is controlled by the concentration of magnesium ions, Silverman said.

In work not yet published, the researchers have also shown that the effects of the DNA constraint on the RNA structure can be modulated by external stimuli such as DNA oligonucleotide strands, protein enzymes and chemical reagents.

While Silverman and Miduturu are currently usi
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