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This is Scientific American's 60-second science. I'm Christopher in Taliatta.

Of the many puzzles mathematicians ponder, one of them is new ways to tie knots.

There are more than 6 billion different types of knots that are being tabulated by mathematicians, 6 billion.

David Lee, a chemist at the University of Manchester in the UK.

The hard part, he says, is actually making them. Just because I can see a knitted jumper doesn't

mean that I can actually make one. Because what Lee and his colleagues are interested in is tying

molecular knots, using strands that are 10,000 times thinner than a human hair. With a molecule, you can't just grab hold of the ends and tie them like you with a shoelace.

They're too small for that.

And instead you've got to use chemistry to make the molecules sort of fold themselves round

into the precise way that you need to form the particular knot.

Continuing the shoelace analogy, remember when you were learning to tie your shoes,

your mom or dad put a finger in the middle of the knot to make it easier to tie?

Well, Lee and his team did something similar, but they used metal ions as the fingers

to keep the knot tying organized.

Then tiny molecular strands, just 192 atoms long, assembled themselves around the ions.

And then mum pulls a finger out and we extract the metal ions out and you're left just

with the knot at the end.

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