Affiliation: | a New York Structural Biology Center, 89 Convent Avenue, Park Building at 133rd St., New York, NY 10027, USA b Department of Chemistry, The City College of New York, 160 Convent Avenue, New York, NY 10031, USA c Graduate Center of the City University of New York, 365 5th Avenue, New York, NY 10016, USA d Département de Chimie, Ecole Normale Supérieure, and CNRS, UMR 7203; 24 rue Lhomond, 75231 Paris cedex 05, France |