1. Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, U.K.
2. Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, Avenida Augusto de Lima 1715, Belo Horizonte 30190-002, Brazil
3. Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London WC1N 3BG, U.K.