1. Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003, U.S.A.
2. Institute for Research in Biomedicine (IRB Barcelona), Carrer de Baldiri Reixac, 10, 08028 Barcelona, Spain
3. Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, NY 10012, U.S.A.