1. Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853
2. Nara Institute of Science and Technology, Ikoma, Nara 630-0101
3. Institute of Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0035, Japan
4. Abteilung VFB, Roche Vitamins Ltd., CH-4070 Basel, Switzerland
5. Integrated Genomics, Chicago, Illinois 60612