Matthew Addicoat, Senior Lecturer in Functional Materials, Nottingham Trent University
The 2026 Nobel prize for chemistry has been awarded to two researchers for their work on mirror-image molecules.
Frances’s Henri Kagan and Japan’s Kensō Soai were announced as this year’s winners during a news conference in Stockholm.
Some molecules, like amino acids, the building blocks of proteins in living beings, exist in two forms that are each other’s mirror-image – like our left and right hands. Molecules that are mirror-image in this way are described as chiral, which is from the Greek word for hand.
Henri Kagan was born at Boulogne-Billancourt, France, in 1930. He is an emeritus professor at the Université Paris-Saclay. Kensō Soai was born at Hiroshima, Japan, in 1950. He is a lecturer at the Tokyo University of Science.
Kagan and Soai developed reactions to produce only one variant of a mirror-image molecule. Their work was decisive for chemists manufacturing medicines, where only one version of a drug molecule might have the desired effect in the body.
Mirror-image molecules are remarkably common and each form can have very different effects. For instance, one version of the substance limonene smells like orange, whereas the other variant of limonene smells like lemon.
Similarly, the molecule carvone exists in left and right hand variants. One form is responsible for the smell in caraway seeds and is used to stop potatoes spoiling, the mirror-image molecule smells like mint and is used to repel mosquitoes.
We can smell these different mirror-image molecules easily, because the receptors in our noses are built from amino acids that are all left handed.
A left hand doesn’t fit well into a right hand glove. Similarly, in biology, a left hand molecule fits differently than a right hand molecule into a receptor built from left hand amino acids.
When we consider chiral molecules, two questions arise: First, when we do a chemical reaction, we often make a mixture of the two mirror images – or enantiomers. This can be a problem when developing pharmaceuticals, for reasons we’ve already mentioned. How can we make exclusively a single mirror image?
Second, Life is chiral because amino acids, exist naturally only in left handed forms. This has important knock on effects. But how did this left handed preference arise on Earth?
Henri Kagan took a major step forward in 1986, when he found a new way to manipulate chemical reactions. Kagan started with a catalyst that was itself chiral. A catalyst is a substance that speeds up a chemical reaction without being consumed in the process.
Kagan then showed how a mixture of the left and right hand versions of the catalyst could enhance the percentage of either the left or right hand form of the product.
In 2003, Soai addressed the second question: how can we start from no chirality and end up with solely the left or right hand variant of a chiral product?
To do this, he used a chemical reaction that is auto-catalytic – meaning that the product of the reaction is also the catalyst for the reaction.
Once the chiral product forms, it then catalyses the formation of only the left or right hand product. In this case, while initially both the left and right hand versions of the product will form, a tiny initial difference becomes self-reinforcing.
This allows one version of a molecule to take over. It can eventually comprise 99.99 per cent of the eventual product.
We don’t know the conditions on Earth four billion years ago that caused only left handed amino acids to form naturally. But Soai showed for the first time since the dawn of life that it is indeed possible to exclusively create one version of a mirror image molecule “from scratch”.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
(The Conversation/MSM)