Nearly two decades after the discovery of knotted proteins, most researchers think the strangely tangled molecules are too unwieldy to play much part in a cell's activities. This notion is changing.

Tie a trefoil knot in a piece of string, seal the ends together, and try to wiggle it free without cutting. In three-dimensional space, the knot holds firm. Add a fourth spatial dimension, however, ...

Proteins are long chains of amino acids that are essential building blocks for all living things. These chains form complex three-dimensional shapes that play a key part in their function—when ...