1. School of Pharmacy Institute for Drug Research, Faculty of Medicine, The Hebrew University of Jerusalem, P.O. Box 12065, Jerusalem 91120, Israel, Given Imaging, New Industrial Park, P.O. Box 258, Yokneam 20692, Israel, and Laboratory of Membrane and Liposome Research, The Hebrew University of Jerusalem, Faculty of Medicine Institute for Medical Research, Israel-Canada, P.O. Box 12272, Jerusalem 91120, Israel