1. Department of Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea
2. Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea
3. Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607
4. Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556
5. School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong 999077, China
6. Department of Biochemistry and Molecular Biology, Indiana University School of Medicine-South Bend, South Bend, Indiana 46617