Have a look round Ken Dill’s office, and you can probably guess his line of work. On the blackboard, drawings of knotted and tangled strings fight it out for space. Books lie open on the desk, their pages cluttered with diagrams of strings. And on the computer screen, stringy chains of yellow, luminescent beads wriggle and writhe. On the evidence, you might guess that Dill is a string theorist.
In a sense, you’d be right. But Dill is no quantum physicist seeking a Theory of Everything. He’s not even doing what most people would think of as physics. Try biology instead. At the University of California at San Francisco, Dill is trying to create a mathematical theory for the building blocks of the living world—those strange and stringy molecules called proteins.
Biologists know a vast amount about proteins: as long chains of amino acids folded into distinctive blobs, they do everything from catalysing chemical reactions to destroying microbes in the bloodstream. But smack bang in the middle of this understanding is a yawning gap—how proteins fold up. The folded shape of a protein is vital to its action—an extra kink or a missing coil can spoil everything. Even when researchers know a protein’s precise sequence of amino acids, they are usually powerless to predict its final shape.
Go one step deeper and the puzzle becomes more disconcerting. After half a century, scientists still haven’t worked out the basic mechanisms by which proteins manage to fold at all. Worse yet, simple arithmetic says that protein folding ought to be impossible. But this is where Dill’s mathematical “string theory”…
