1. Magnetic Resonance Center (CERM) and Department of Chemistry, University of Florence, 50019 Sesto Fiorentino (FI), Italy, Department of Biology, University of Rome “Tor Vergata”, 00133 Rome, Italy, National Institute of Biostructures and Biosystems (INBB), Viale delle Medaglie d’Oro 305, 00136 Rome, Italy, and Department of Chemical Science and Technology, University of Rome “Tor Vergata”, 00133 Rome, Italy