1. Magnetic Resonance Center, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Italy, Department of Chemistry, University of Florence, Via Della Lastruccia 5, 50019 Sesto Fiorentino, Italy, FiorGen Foundation, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Florence, Italy, and Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095-1569