1. UCLA-DOE Institute for Genomics and Proteomics, Los Angeles, California 90095, United States
2. Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
3. Molecular Biology Institute, University of California, Los Angeles, California 90095, United States
4. Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California 90095, United States