of new antibiotics as well.

Yonath, is professor of structural biology and director of the Helen & Milton A. Kimmelman Center for Biomolecular Structure & Assembly at the Weizmann Institute. Yonath, in collaboration with the late biochemist H. G. Wittmann of Max Planck Institute for Molecular Genetics, Berlin, was the first to obtain crystals of the ribosome, a prerequisite to the X-ray crystallographic studies honored with this year's prize. Later, she and her coworkers studied ribosome structure with cryo-crystallography, obtained X-ray crystal structures of the small and large subunits, revealed the binding sites of several antibiotics, and proposed modes of action for the drugs. She is an Israeli citizen.

The contributions of Steitz, professor of chemistry and of molecular biophysics & biochemistry and a Howard Hughes Medical Institute Investigator atYale, have included a structure of the large subunit, obtained by a group led by him and his Yale colleague Peter B. Moore. This study helped show that the ribosome is actually a ribozyme (RNA-based enzyme) by revealing that RNA predominates in the active site. The group later determined structures of the large subunit bound to various substrates, such as antibiotics and transition-state analogs.

Ramakrishnan, now senior scientist and group leader at the Structural Studies Division of the MRC Laboratory for Molecular Biology, is a U.S. citizen born in India. His group's contributions have included determination of the crystal structure of the small subunit and a demonstration of how the ribosome discriminates between correct and incorrect tRNAs, which deliver specific amino acids to the ribosome for protein synthesis.

American Chemical