1. Center for Biomedical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, Catalysis Science Laboratory, Mitsui Chemicals, Inc., 1144 Togo, Mobara-shi, Chiba 297-0017, Japan, and Center for Environmental Biotechnology and Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee