NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the task group responsible for the report were chosen for their special competences and with regard for appropriate balance.

Support for this project was provided by Contract NASW 96013 between the National Academy of Sciences and the National Aeronautics and Space Administration. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsor.

Images on the front cover:

Top left: Red blood cells in a cross section of a small blood vessel in the mouse lung. Scanning electron micrograph courtesy of Jacob Bastacky, Lawrence Berkeley National Laboratory.

Top right: A ligand complex, a designed, sequence-specific minor groove binding compound (Geierstanger et al., 1996). Image courtesy of David Wemmer, University of California at Berkeley.

Bottom left: Nitrogen Regulatory Protein C (NtrC), a bacterial transcription factor regulated by phosphorylation (Volkman et al., 1995). Image courtesy of David Wemmer, University of California at Berkeley.

Bottom right: The apicoplast is a nonphotosynthetic plastid, acquired by endosymbiosis of a eukaryotic alga and retention of the algal chloroplast. This essential organelle is found in all members of the phylum Apicomplexa, including malaria parasites and the AIDS pathogen Toxoplasma gondii (shown), providing a promising target for therapeutic drug design (Köhler et al., 1997). Electron micrograph courtesy of David Roos and Lewis Tilney, University of Pennsylvania.

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