Two Chemists Win Nobel Prize for Unraveling a Mystery of Molecular 'Handedness,' Helping Drugmakers Develop Safer Medications

Two scientists have been awarded the Nobel Prize in Chemistry for their work untangling a perplexing puzzle about the “handedness” of molecules, allowing drugmakers to develop safer, more precisely targeted medicines. Chemists Henri Kagan of the University of Paris-Sud and Kenso Soai of the Tokyo University of Science were named Nobel laureates on October 7. Kagan and Soai’s award-winning research centers on chirality, which derives from the Greek word for “hand.” Some molecules come in two forms that are mirror images of each other, just like our right and left hands.

These mirror images, known as chiral forms, may look similar, but they can behave very differently. The chemical carvone, for instance, can smell like mint or caraway, depending on which version of it you sniff. However, living organisms usually contain just one version of a molecule.

The sugars in our DNA, for example, are right-handed, while most amino acids in your body’s proteins are left-handed. Their mirror-image counterparts, by contrast, are rarely found in nature. This phenomenon is known as homochirality, which derives from the Greek words for “same” and “hand.” For decades, this chemical asymmetry confounded scientists.

How do natural reactions in living organisms produce just one type of a molecule? And why did life’s building blocks evolve a preference for one version or the other? Deepening the conundrum, they couldn’t replicate this natural asymmetry in the lab.

Their experiments produced equal amounts of each version of a molecule—a 50-50 right-handed and left-handed split. Thanks to Kagan and Soai, as well as numerous scientists who came before them, researchers are now closer to unraveling this mystery. Their work hinges on catalysts, or substances that can influence chemical reactions without being used up or permanently altered in the process.

In 1986, Kagan reported that if an asymmetrical catalyst is introduced to a chemical reaction, it can cause the resulting molecule to be asymmetrical, too, producing more of the right-handed or left-handed version. The effect of the catalyst is nonlinear, meaning that a small imbalance in the catalyst can lead to a much larger imbalance in the handedness of the ensuing molecules. Soai further tweaked the work and developed chemical reactions that can produce their own asymmetrical catalyst.