Per Artursson1, Stefan D Knight2. 1. Department of Pharmacy and Science for Life Laboratories, Uppsala University, 751 23 Uppsala, Sweden. per.artursson@farmaci.uu.se stefan.knight@icm.uu.se. 2. Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, SE-751 24 Uppsala, Sweden. per.artursson@farmaci.uu.se stefan.knight@icm.uu.se.