1. Department of Chemistry Science and Technology, University of Rome “Tor Vergata”, 00133 Rome, Italy; Section B of I.N.F.M. Roma-II, 00133 Rome, Italy; Section B of I.N.F.M. Roma-I, 00185 Rome, Italy; POLY-tech, Area Science Park, Padriciano 99, 34012 Trieste, Italy; and Department of Biochemistry, Biophysics, and Macromolecular Chemistry, University of Trieste, 34127 Trieste, Italy