1. Molecular Logic Gate Laboratory
2. Department of Chemistry, and School of Molecular Science (BK 21), Korea Advanced Institute of Science and Technology (KAIST), 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea
3. School of Biological Sciences, Seoul National University, Seoul, Korea
4. Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027