1. Departments of Molecular Biophysics and Biochemistry; Yale University; New Haven CT 06520-8114
2. Department of Biological Information, Graduate School of Bioscience and Biotechnology; Tokyo Institute of Technology, Yokohama-shi; Kanagawa 226-8501 Japan
3. Departments of Molecular Biophysics and Biochemistry and of Chemistry; Yale University; New Haven CT 06520-8114