Chemistry.

And this year's Nobel Prize in Chemistry goes to three scientists for their discovery in the early 1980s of how cells mark proteins for destruction. The key turned out to be the molecular tag called ubiquitin. Doomed proteins get the label and then are shuttled off to a cell's disposal apparatus, called a proteasome, which slices the proteins into pieces. This selective destruction of unwanted proteins is involved in a number of diseases, including cervical cancer and cystic fibrosis.

Aaron Ciechanover and Avram Hershko of the Technion-Israel Institute of Technology in Haifa and Irwin Rose of the University of California, Irvine will share the prize, which was announced at press time. More on their research will appear in next week's Science News.