1. Laboratory of Nucleic Acids Chemistry and Laboratory of Chemical Cybernetics, Department of Chemistry, M.V. Lomonosov Moscow State University, Leninskie Gory 1, 119992 Moscow, Russia, and Group “Réparation de l'AND”, UMR 8126 CNRS, Univ Paris-Sud, Institute Gustave Roussy, 94805 Villejuif Cedex, France