It's not just people who come in right- or left-handed models. Some molecules occur in two forms, called enantiomers, that differ only in the spatial arrangement of their atoms such that they are mirror images of one another. So like our hands, no matter how you twist and turn them, these molecules can't overlap and don't have the same three-dimensional structure. This property, known as chirality, has important ramifications because many biological receptors accept only one form of these molecules. What's more, the wrong form may actually do more harm than good.

This year's recipients of the Nobel Prize in ChemistryWilliam S. Knowles, Ryoji Noyori and K. Barry Sharplessare honored for their work developing chiral molecules as catalysts. Catalysts speed up a reaction but do not get consumed. Most important, the catalysts refined by the winners heavily favor the synthesis of one enantiomer product molecule over the other. This discovery of catalytic asymmetric synthesis opened up a completely new field of research, according to the Nobel committee. For their efforts, Knowles and Noyori share half the prize, and Sharpless receives the other half.

  • William S. Knowles(below at left), now retired, discovered the first example of catalytic asymmetric synthesis in 1968 while he was a chemist for the Monsanto Corporation. He developed a chiral transition metal catalyst for hydrogenation, a reaction in which hydrogen is added across a molecule's double bond. His discovery allowed for the subsequent development of an industrial process for the production of L-DOPA, which is used in treating Parkinson's disease.

  • Ryoji Noyori(below center) of Nagoya University in Japan built on Knowles's discovery and vastly improved the efficiency and applicability of chiral catalysts for hydrogenation reactions that produce only one enantiomer in industrial applications.

  • K. Barry Sharpless(below at right) of the Scripps Research Institute in La Jolla, Calif., was honored for developing chiral catalysts for a different class of reactions known as oxidations. Of particular note is his development of a process to produce only one form of glycidol, a molecule used in the pharmaceutical industry to manufacture cardiac medications known as beta blockers.