1. Contribution from the Physical Organic Chemistry Unit, Stratingh Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, BioMaDe Technology Foundation, Nijenborgh 4, 9747 AG Groningen, The Netherlands, Department of Membrane Cell Biology, University of Groningen, Faculty of Medical Sciences, Antonius Deusinglaan 1, 9700 AD Groningen, The Netherlands, and Kiadis BV, Zernikepark 6-8, 9747 AN Groningen, The Netherlands