1. Department of Chemistry, Southern Methodist University, Dallas, Texas 75275, United States
2. State Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, China
3. China Research Center, Genencor, A Danisco Division, Shanghai 200335, China
4. Department of Chemistry, California State Polytechnic University, Pomona, California 91768, United States