The use of aqueous two-phase systems for the partitioning of macromolecules, organelles and cells was originally developed by Per-Ake Albertsson in Sweden in the mid-fifties [1-3]. These systems were initially applied to separations of plant organelles and viruses but their use has now extended into most areas of cell biology and biochemistry [4,5]. Since 1979 biennial International Conferences on Partitioning in Aqueous Two-Phase Systems have been...