1. Department of Physiology and Biophysics, University of California, Irvine, California 92697, United States
2. Department of Life Science and Interdisciplinary Program of Integrated Biotechnology, Sogang University, Shinsu-Dong 1, Mapo-Gu, Seoul 121-742, Korea
3. Department of Chemistry, Norwegian University of Science and Technology, 7491 Trondheim, Norway