RACHEL MARTIN, HOST:
Diplomacy can be its own kind of tricky knot. But tying a literal knot can be really difficult - just ask any kid who's struggling with shoelaces. Now imagine how much harder it would be to make a knot in a molecule. That's what some scientists have been trying to do. NPR's Nell Greenfieldboyce reports on the tightest knot ever tied.
NELL GREENFIELDBOYCE, BYLINE: Knots may not seem high-tech. But once our prehistoric ancestors figured out knots, it led to all kinds of innovation.
DAVID LEIGH: Like fishing nets and axes with blades tied to the handles.
GREENFIELDBOYCE: David Leigh is a chemist at the University of Manchester in the United Kingdom. And he says knots could be just as revolutionary at the molecular level.
LEIGH: But we can't exploit that until we learn how to make them.
GREENFIELDBOYCE: The first molecular knot made by a chemist had three loops. It looked a bit like a three-leaf clover. Leigh says that's the simplest kind of knot possible.
LEIGH: And then, for the next 25 years, chemists weren't able to make any more complicated knots than that.
GREENFIELDBOYCE: Which is surprising considering that mathematicians have come up with billions of possible knots. Well, just in the last few years, scientists have managed to produce a couple of more complex knots. And now, in the journal Science, Leigh and his colleagues have unveiled the most intricate one yet. It looks a lot like a Celtic knot, and making this out of molecules wasn't easy.
LEIGH: You can't tie the knots by grabbing the ends and mechanically tying them like you would a shoelace in our everyday world. Instead, you have to use chemistry.
GREENFIELDBOYCE: Leigh's team designed strands of atoms that could effectively braid themselves together in a test tube.
LEIGH: And being able to braid, like you braid a girl's hair in elementary school, allows you to make much, much more complicated knots and ultimately opens the door for weaving as well, which will be very exciting.
GREENFIELDBOYCE: Because molecular weaving could produce materials with interesting new properties.
Edward Fenlon is a chemist at Franklin & Marshall College who has a special interest in knots. He says this new one is fantastic.
EDWARD FENLON: It's really impressive that they've been able to go beyond some of the more simple knots with just three crossings.
GREENFIELDBOYCE: He says this knot has eight crossings, and that makes it the tightest knot ever. Here's how he assesses tightness.
FENLON: So it's just the length of the rope and then how complex the knot is, how many crossings you have.
GREENFIELDBOYCE: In this case, the rope, if you will, is very short - just 192 atoms long, 500 times smaller than a red blood cell.
Nell Greenfieldboyce, NPR News.