1. Instituto de Química Médica (C.S.I.C.), Juan de la Cierva 3, E-28006 Madrid, Spain
2. Laboratory of Medical Biochemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium
3. Rega Institute for Medical Research, Katholieke Universiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium