1 Cell Biology and Biophysics Unit, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA.
2 Biochemistry & Biophysics Center, National Heart, Lung and Blood Institute, Bethesda, MD, USA.
3 Mass Spectrometry Core Facility, National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA.
4 Department of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada.
5 University of Texas Southwestern Medical Center, Protein Chemistry Technology Center, Dallas, USA.
6 Cell Biology and Biophysics Unit, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA. Antonina@mail.nih.gov.
7 Biochemistry & Biophysics Center, National Heart, Lung and Blood Institute, Bethesda, MD, USA. Antonina@mail.nih.gov.