A half-meter-long protein floats in midair, several centimeters in front of a monitor. It looks like an oversize curled ribbon from a birthday package. As three molecular biologists maneuver around the image, studying the complex molecule from different angles, it begins to fold, slowly twisting and interlocking into a tangled knot. Its shape is a clue to the function it performs in the human body: some proteins produce chemical reactions or behave like a kind of scaffolding for cells, while others help with cell division. Creation of a drug that encourages or blocks a protein's action-say, preventing cancerous cells from dividing-could lead to more effective treatments. One of the researchers uses a stylus to prod the protein at several points. As she does so, the protein refolds itself, revealing a location that could be targeted with a drug to inhibit the protein's function.

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