1. Department of Biology and Chemistry; City University of Hong Kong; 83 Tat Chee Avenue, Kowloon Hong Kong, P. R. China
2. Department of Chemistry; University of Hong Kong; Pokfulam Road Hong Kong
3. Department of Chemistry; Youngstown State University; One University Plaza Youngstown, OH 44555 USA
4. Department of Chemistry; Purdue University; 560 Oval Drives West Lafayette IN 47907 USA