1. Plant Pathology, Swammerdam Institute for Life Sciences, University of Amsterdam, P.O. Box 94062, 1090 GB Amsterdam, The Netherlands (M.R., J.H.V., A.D.d.B., P.M.H., B.J.C.C.);
2. Mass Spectrometry, Swammerdam Institute for Life Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands (H.L.D., J.W.B., C.G.d.K.); and
3. Biochemistry, Academic Medical Center, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands (D.S.)