1. Department of Chemistry, Center for Integrated Molecular Systems, Division of Molecular and Life Sciences, and Polymer Research Institute, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang 790-784, Republic of Korea, and Department of Microbiology, Dongguk University College of Medicine, 707 Seokjang-dong, Gyeongju, 780-714, Republic of Korea