Caltech scientists create DNA tubes with programmable sizes for nanoscale man...( PASADENA Calif.--Scientists at the C...)

PASADENA, Calif.--Scientists at the California Institute of Technology (Caltech) have developed a simple process for mass producing molecular tubes of identical--and precisely programmable--circumferences. The technological feat may allow the use of the molecular tubes in a number of nanotechnology applications.

The molecular tubes are composed of wound-up strands of DNA. DNA has been considered an ideal construction material for self-assembling molecular structures and devices because two complementary DNA strands can automatically recognize and bind with each other. DNA has been used to form rigid building blocks, known as tiles, and these tiles can further assemble into extended lattice structures, including tubes. However, it has been difficult to control the diameters of such tubes.

Peng Yin, a senior postdoctoral scholar in bioengineering and computer science at Caltech's Center for Biological Circuit Design, along with his colleagues has designed a series of flexible, single-stranded DNA molecules, called single-stranded DNA tiles. Each single-stranded tile is exactly 42 bases long and contains four modular binding sites. By pairing up the complementary binding sites, these single-stranded tiles bind with each other in a particular orientation like Lego pieces snapped together, forming a tube composed of parallel DNA helices.

The circumference of the resulting tube is determined by the number of different 42-base pieces used in its construction. For example, four pieces create a tube with a circumference of 12 billionths of a meter (or 12 nanometers); five pieces, a 15-nanometer-circumference tube; and six pieces, an 18-nanometer tube.

"We are not the first to make DNA tubes with controlled circumferences. However, compared with previous approaches, our method is distinctively simple and modular," says Yin. The simplicity and modularity of their approach permits the description of the tube design using a simple grap
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