1. Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Department of Molecular Biology, Hebrew University-Hadassah Medical School, P.O.B. 12000, Jerusalem 91120, Israel, Institute of Organic and Medicinal Chemistry, University of Pécs, H-7643 Pécs, Hungary, and Department of Chemistry, Nuclear Chemistry, The Royal Institute of Technology, S-10044 Stockholm 70, Sweden