科学美国人60秒 SSS 看结容易 打结难（在线收听）

Knot Not Easy to Knot

看结容易 打结难

Of the many puzzles mathematicians ponder, one is new ways to tie knots. "There are more than six billion different types of knots that have been tabulated by mathematicians. Six billion." David Leigh, a chemist at the University of Manchester in the U.K.

在数学家思考的众多的谜题中，其中一个就是打结的新方法。“数学家们已经想出了60亿种不同的打结方法。”大卫·利是英国曼彻斯特大学的化学家。

The hard part, he says, is actually making them. "Just because I can see a knitted jumper doesn't mean I can actually make one." Because what Leigh and his colleagues are interested in, is tying molecular knots—using strands that are 10,000 times thinner than a human hair.

他还表示，困难之处在于打结的过程。“因为，我可以看懂针织毛衣，并不意味着我可以织一个毛衣。”因为，利和他同事感兴趣的是打“分子”结——使用的线比人类的头发还细1万倍。

"With a molecule you can't just grab hold of the ends and tie them like you would a shoelace. They're too small for that. Instead you've got to use chemistry to make the molecules fold themselves round into the precise way you need to form the knot."

“你不能像绑鞋带一样来抓分子的末端。因为它们太小了。你必须让分子按照需要的精确的方式自己折叠打结。”

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? Leigh and his team did something similar, but 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.

继续鞋带的类比分析——想想你学习系鞋带的时候，你的妈妈或者爹地会把手指放到结的中间，这样会更容易打结?利和他的团队做了类似的事情，但是他们使用金属离子作为“手指”组织打结。之后，小的分子线头，只有192原子长，围绕金属离子折叠。

"And then mum pulls her finger out—we extract the metal ions out—and you're left with just the knot at the end." The most complex molecular knot ever synthesized. The study is in the journal Science.

“然后妈妈将自己的手指抽出——我们将金属离子提取——最后就只剩下打得结了。” 这是复杂的分子结。该研究结果发表在《科学》杂志上。

Knots were hugely useful to our ancestors in the stone age: "fishing nets, axes with blades tied to the handles, how to weave fabrics to keep him warm." And Leigh says knots could be just as helpful in the molecular world—like for stronger braided polymers—maybe a better Kevlar.

在石器时代打结对于我们的祖先非常的有用:”渔网、有把手的斧头，以及如何编织可以让他们暖和。”利表示在分子世界，结也一样非常有用——像更坚韧的辫状聚合物——或许是更好的Kevlar。

After all, we do have six billion knots to choose from. "As every Boy Scout knows, different types of knots have different characteristics that make them more or less suited to particular tasks." And yes, Leigh himself was once a Scout. "I found knots difficult to tie then, and it hasn't gotten easier as I've gotten older."

但是毕竟我们有60亿种结可以选择。“童子军都知道，不同类型的结具有不同的特征,适合于特定的任务。”利自己曾是一名童子军。“当时我觉得打结非常的难，即使后来我年龄变大了也还是觉得如此。”