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takyon writes:

The tightest molecular knot ever has been created, using 192 atoms:

In a feat that breaks one of the most obscure world records in science, a team of chemists has created a microscopic circular triple helix, or put in more simple terms, the tightest knot ever made. Researchers in Manchester in the UK built the knot from a strand of atoms which curls around in a triple loop and crosses itself eight times. Made from 192 atoms linked in a chain, the knot is only two millionths of a millimetre wide – around 200,000 times thinner than a human hair.

[...] The tightness of a knot is defined by the distance between points where the rope, string – or chain of atoms, in this case – cross each other. For the Manchester group's circular triple helix, each crossing point is a mere 24 atoms apart. "That's very, very tight indeed," said Leigh. "It is definitely the most tightly knotted physical structure known."

Building molecular knots has become something of a passion for Leigh. The latest knot beats the record his own team set four years ago when they created a so-called pentafoil knot from 160 atoms. That knot bested an even earlier effort called a trefoil knot [DOI: 10.1002/anie.201105012] [DX] with three crossing points. "There are actually billions of different knots known to mathematicians," Leigh said in a comment that hinted at a busy future.

Also at Science Magazine and NPR.

Braiding a molecular knot with eight crossings (DOI: 10.1126/science.aal1619) (DX)

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