1. Department of Biochemistry, Biophysics and Macromolecular Chemistry, University of Trieste, I-34127 Trieste, Italy; Istituto di Studi Chimico-fisici di Macromolecole Sintetiche e Naturali, National Research Council, via De Marini 6, I-16149 Genova, Italy; and Department of Chemistry Science and Technology, University of Rome “Tor Vergata”, I-00133 Rome, Italy