Scientists have accidentally tied the smallest and tightest molecular knot ever, overtaking the top spot in the Guinness Book of World Records. The remarkable microscopic tangle contains just 54 atoms that twist around three times into an interlacing loop called a ‘trefoil’ knot, with no loose ends.
What is a Molecular Knot?
A molecular knot is a chain of atoms that crosses itself at least once, forming a loop with no free ends. Knots can be classified by their shape and complexity, such as how many times they cross themselves. The simplest of nontrivial knots is the trefoil knot, which has three crossings and resembles a three-leaf clover.
Molecular knots are not only fascinating for chemists, but also for biologists, as they can occur naturally in DNA, RNA and proteins. Studying how these knots form and function could help us understand how they affect biological processes, such as gene expression, DNA replication and enzyme activity.
How was the smallest Molecular Knot made?
The smallest knot ever made was created by chemists at the University of Western Ontario in Canada and the Chinese Academy of Sciences. They were working on creating metal acetylides, which are useful for organic chemical reactions, when they stumbled upon the unexpected knot.
The knot is made of a chain of gold, phosphorus, oxygen and carbon atoms that self-assembles into a trefoil shape. The gold atoms act as the backbone of the knot, while the other atoms form the links. The researchers used X-ray diffraction to determine the structure of the knot and confirm its size and tightness.
The knot has a backbone crossing ratio (BCR) of 18, which means that it has 18 atoms in the chain for each crossing. The smaller the BCR, the tighter the knot. The previous smallest molecular knot, reported in 2020, had a BCR of 23.
Why is this discovery important?
The discovery of the smallest and tightest molecular knot ever is not only a remarkable feat of chemistry, but also a potential source of new materials and insights. By understanding how this combination of atoms results in a knot, scientists could design new molecules with novel properties and functions.
For example, molecular knots could be used to create stronger and more flexible polymers, which are chains of molecules that make up plastics and other materials. Molecular knots could also help us mimic natural knots, such as those found in DNA and proteins, and manipulate them for biomedical applications.
The researchers are still trying to figure out why this particular chain of atoms forms a knot at all, and whether they can make even smaller or tighter knots in the future. They are also exploring how the knot behaves under different conditions, such as temperature and pressure.
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