1. Angiogenesis Laboratory, Research Institute Growth and Development (GROW), Department of Pathology, Maastricht University & University Hospital, Maastricht, The Netherlands; Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands, and Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455.