1. Department of Chemistry, Korea University, Seoul 02841, Korea
2. Division of Medical Oncology, Department of Internal Medicine, Korea University College of Medicine, Korea University, Seoul 02841, Korea
3. Brain Korea 21 Program for Biomedical Science, Korea University College of Medicine, Korea University, Seoul 02841, Korea
4. Department of Biomedical Research Center, Korea University Guro Hospital, Korea University, Seoul 08308, Korea
5. Department of Chemistry, The University of Texas at Austin, Austin, TX 78712-1224