1. Department of Physiology and Biochemistry, University of Pisa, I-56126 Pisa, Italy, Institute of Biostructures and Bioimages, CNR, I-80134 Naples, Italy, Institute of Biomolecular Chemistry, CNR, Comprensorio Olivetti, I-80078 Pozzuoli (Naples), Italy, and Proteomics and Mass Spectrometry Laboratory, ISPAAM, CNR, I-80147 Naples, Italy