1. Department of Chemical and Biological Engineering, College of Engineering, Korea University, Anam-Ro 145, Seoul 136-713, Republic of Korea
2. Department of Neurology, Research Institute and Hospital of National Cancer Center, 323 Ilsan Street, Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
3. College of Medicine, Seoul National University, Daehak-Ro 103, Seoul 110-744, Republic of Korea
4. College of Medicine, Chung-Ang University, Heuksuk-Ro 84, Seoul 156-756, Republic of Korea