1. Y. Lu, F. Duewer, X.-D. Xiang, Molecular Design Institute, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
2. T. Wei and P. G. Schultz, Howard Hughes Medical Institute and Molecular Design Institute, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
3. Y. Lu and N.-B. Ming, National Laboratory of Solid State Microstructures, NanJing University, NanJing 210093, China.