1 Department of Neurology, David Geffen School of Medicine, University of California, Gordon Neuroscience Research Building, Room 451, 635 Charles E. Young Drive South, Los Angeles, CA, 90095-7334, USA.
2 Present address: Division of Peptide Biochemistry, Technical University of Munich, Freising, Germany.
3 Faculty of Chemistry, University of Duisburg-Essen, Essen, Germany.
4 Department of Neurology, David Geffen School of Medicine, University of California, Gordon Neuroscience Research Building, Room 451, 635 Charles E. Young Drive South, Los Angeles, CA, 90095-7334, USA. gbitan@mednet.ucla.edu.
5 Brain Research Institute, University of California, Los Angeles, CA, USA. gbitan@mednet.ucla.edu.
6 Molecular Biology Institute, University of California, Los Angeles, CA, USA. gbitan@mednet.ucla.edu.