1. Magnetic Resonance Center (CERM), University of Florence, Via L. Sacconi 6, 50019 Sesto Fiorentino, Italy, Department of Chemistry, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy, Department of Agricultural Biotechnology, University of Florence, Via Maragliano, 75−77, 50144 Florence, Italy, European Molecular Biology Laboratory, Hamburg Outstation, Notkestrasse 85, 22603 Hamburg, Germany, and Institute of Crystallography, Russian Academy of Sciences, Leninsky pr. 59, 117333...