For all the harm they cause, viruses are very simple things, not much more, really, than a short strand of DNA or RNA encased in a box of protein. That simple structure intrigues virologist Mark Young and chemist Trevor Douglas, who have been using the empty husks of viruses to make the world's smallest test tubes.
"Chemists have been trying for years to build small, uniform cagelike structures," says Young, who works at Montana State University in Bozeman. Such microñtest tubes, he says, would allow chemists to design entirely new classes of materials, including perhaps tiny wires, crystals, and other microelectronic components. Their efforts have largely been in vain, however, because they've had trouble making uniformly sized microcontainers in which to conduct their experiments.
Young and Douglas realized that the necessary containers already existed: the protein shells of viruses. "Viruses are incredibly homogeneous in both size and shape," says Douglas, who works at Temple University in Philadelphia. Their shapes range from rods to icosahedrons (symmetrical 20-sided objects). So instead of building containers from scratch, Young and Douglas grow viruses in culture, chemically separate the viral genetic material from the protein shell, and then reassemble the shell.
To test their idea, Young and Douglas immersed some empty viral shells in a solution containing tungsten salt. The acidity of the solution, it turns out, controls whether pores on the viral cages remain open or shut. After the pores close, the tungsten molecules trapped inside react and form uniform crystals that exactly mirror the shape of the viral container. Since viruses come in so many forms and sizes, Young and Douglas see the potential to build scores of different materials. "It's really a very simple idea when it comes right down to it," says Young. "But no one had thought of it before."