Using viruses to make nanowires

To Angela M. Belcher of MIT, viruses and their DNA provide a versatile means for making nanoscale materials and gadgets. "What you have is these DNA sequences that code for the growth and assembly of a functional device," Belcher says. In her latest foray into "virus-enabled synthesis," Belcher and seven colleagues tweaked the genome of the rod-shaped virus M13 so that each of its roughly 2,700 major coat proteins would sport a string of four glutamate molecules. In water, the negative charges of these appendages proved irresistible to cobalt ions, which once in place on the viral surface could then be readily oxidized. The result: cobalt oxide wires the size and shape of M13 viruses (Science, published online April 6, dx.doi.org/10.1126/science.1122716). One goal is to make electrodes for tiny batteries. That's why Belcher's group used another genetic technique to weave a 12-amino-acid motif that binds gold atoms into some of the coat proteins. The hybrid gold-cobalt oxide nanowires produced have energy capacities almost one-third higher than that of cobalt oxide-only nanowires.