1. Department of BioSystems, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Korea, Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Korea, Department of Chemistry, Yonsei University, Seoul 120-749, Korea, and Department of Allergy and Clinical Immunology, Ajou University School of Medicine, Suwon 442-749, Korea