1. Department of Chemistry and Division of Nano Science, Ewha Womans University, 11-1 Daehyon-Dong, Sodaemun-Ku, Seoul 120-750, South Korea, and Interdisciplinary Program of Biochemical Engineering and Biotechnology, Seoul National University, San 56-1, Shilim-dong, Gwanak-gu, Seoul 151-742, South Korea %jyoon@ewha.ac.kr