1. Center for Biophysics and Quantitative Biology; University of Illinois at Urbana-Champaign; 1110 West Green Street Urbana IL 61801 USA
2. Department of Chemistry; University of Illinois at Urbana-Champaign; 600 South Matthews Avenue Urbana IL 61801 USA
3. Industrial Enzymes National Engineering Laboratory; Tianjin Institute of Industrial Biotechnology; Chinese Academy of Sciences; Tianjin 300308 PRC
4. Institute of Biological Chemistry; Academia Sinica; 128 Academia Road Taipei 11529 ROC