1. Department of Biochemistry, Max Planck Institute for Chemical Ecology, Jena D-07745, Germany
2. Section of Cell and Developmental Biology, University of California, San Diego, California 92093-0380, USA
3. Research Group Biosynthesis/NMR, Max Planck Institute for Chemical Ecology, Jena D-07745, Germany
4. Scripps Institution of Oceanography, University of California, San Diego, California 92093, USA