1. From the Department of Medical Biochemistry (R.A.B., J.O.F., O.L.V., F.W., H.P., A.J.G.H.), Academic Medical Center, University of Amsterdam; the Department of Molecular Cell Biology (E.P., P.t.D.), Leids Universitair Medisch Centrum, Leiden University; and the Division of Biopharmaceutics (E.J.A.v.W., J.K.), Leiden/Amsterdam Center for Drug Research, Gorlaeus Laboratories, Leiden, The Netherlands.