( ther the three strands will bind to ea...)Self-assembled DNA buckyballs for drug delivery

ther, the three strands will bind to each other over the complementary portions, creating a Y-shaped molecule. By joining several Y's in the same way, Luo's research group created molecules with several arms, a sort of tree shape (dendri- means tree in Greek). Then they attached polystyrene molecules to the dendrimerlike DNA forming a hybrid molecule called an amphiphile -- a molecule that both likes and hates water. DNA is hydrophillic -- attracted to water -- while polystyrene is hydrophobic -- water repels it.

The researchers expected the amphiphiles to assemble in water into some sort of solid structure arranged so that DNA would have a maximum interaction with water and polystyrene would avoid water as much as possible. Other researchers have used other amphiphiles to make spheres, rods and other solids. The hollow buckyballs were an intriguing and serendipitous surprise. A model suggests that one buckyball consists of about 19,000 amphiphiles, with their water-loving DNA mostly on the outside of the rods that form the structure. How these tens of thousands of molecules were able to self-organize to form such an intricate and complex structure is still an open question, the researchers say. They are seeking collaborators to solve the puzzle.

Luo and Ph.D. graduate students Soong Ho Um, Sang Yeon Kwon and Jong Bum Lee described DNA buckyballs in an invited talk titled "Self-assembly of nanobuckyballs from dendrimer-like-DNA-polystyrene amphiphiles" Sunday, Aug. 28, at the 2005 annual meeting of the American Chemical Society in Washington, D.C. They reminded the audience that although the geometry of solid truncated icosahedrons was first described by Archimedes on paper more than 2,000 years ago, the skeletal, hollow-faced version of buckyballs had not been envisioned until Leonardo da Vinci's illustrations in 1494.

Luo added that DNA buckyballs may turn out to have unusual electronic, photonic and mechanical properties, and that becau
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Source:Cornell University News Service

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