In a clever bit of engineering that exploits the structure of one molecule and the strength of a second, chemists have melded DNA strands with buckminsterfullerenes, the soccer ball-shaped molecules of pure carbon. The achievement, reported in the current Angewandte Chemie International Edition, may provide a simple, rapid way to create custom-made polymers.
Researchers weren't seeking this result. It's an offshoot of another idea they were testing--using buckyballs as a way to spot DNA with a transmission electron microscope (TEM). Buckyballs are dense enough to be seen by a TEM, but DNA isn't. To make DNA visible, a team at the University of South Carolina, Columbia--including chemists James Tour, Alan Cassell, and Walter Scrivens--attached positively charged ammonium groups to the neutral buckyballs, then mixed the buckyballs with rings and strands of DNA. They hoped that the positively charged buckyballs would attach to the negatively charged DNA backbone. "We thought this would be a great way to image DNA," says Tour. To check, the researchers examined slides of the mixture with TEM. Indeed, the buckyballs were arranged in the telltale rings and zigzags of DNA.
The team then realized that the DNA was acting like a molecular scaffold for the buckyballs, which almost completely coated the DNA surface. It is extremely difficult to assemble buckyballs into strings of exact size for use as transistors and wires, because once they reach a certain length they are hard to purify and manipulate. But with DNA as a template, Tour says, "we can use nature's materials to just shake and bake," cooking up custom-made fullerene polymers that mimic the size and shape of a given DNA helix. Next, Tour's group will try to link the coat of fullerenes together to form polymers, which might be used as molecular wires, since fullerenes can conduct electricity.
"It's a terrific paper," says Rice University chemist Dan Colbert, who sees the study as an important advance toward creating nanoscale molecular structures. Tour and his colleagues are currently testing the ability of the modified buckyballs to enhance images of synthetic cube- and star-shaped DNA.