1. Magnetic Resonance Center (CERM), University of Florence, Via L. Sacconi 6, 50019 Sesto Fiorentino, Italy
2. Department of Chemistry, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy
3. Department of Agricultural Biotechnology, University of Florence, Via Maragliano 75-77, 50144 Florence, Italy