1. Department of Chemistry and Biochemistry, University of Texas, 1 University Station, A5300, Austin,
Texas 78712-0165, United States
2. Department of Experimental Therapeutics, UT M. D. Anderson Cancer Center, 1515
Holcombe Boulevard, Unit 1950, Houston, Texas 77030, United States
3. Lumiphore, Inc., 4677 Meade Street, Richmond,
California 94804, United States
4. Department of Chemistry, Yonsei University, Seoul 120-749, Korea