1. Global Environment Research Group, Environment & Structure Laboratory, Korea Electric Power Research Institute, 103-16 Munji-Dong, Yuseong-Gu, Daejeon 305-380, Korea, and Departments of Chemistry and Bioinformatics and Life Science and CAMDRC, Soongsil University, 1-1 Sangdo-Dong, Dongjak-Gu, Seoul 156-743, Korea