1. Division of BiologyCalifornia Institute of Technology Pasadena California 91125
2. Department of Medical Biochemistry and BiologyUniversity of Bari 70124 Bari Italy
3. Department of Biological and Environmental Science and TechnologyUniversity of Lecce I‐73100 Lecce Italy
4. Institute of Clinical Neurology, University of Milan Ospedale Maggiore Policlinico 20122 Milan