1. Department of Chemistry and Division of Nano Sciences, Ewha Womans University, Seoul 120-750, Korea, Department of Chemical Technology, Changwon National University, Kyungnam 641-773, Korea, Department of Pharmacology and Laboratory of Neurodegenerative Diseases, Ewha Institute of Neuroscience, Seoul 120-750, Korea, and Department of Chemistry, Sogang University, Seoul 121-742, Korea wwnam@ewha.ac.kr