Published online by Cambridge University Press: 10 February 2011
We present a new method for electrophoretic separation of DNA, Ferro fluid Array Electrophoresis (FAE). The method uses a stabilized suspension of an hydrophobic ferrofluid in aqueous buffer as the separating medium. When this suspension is placed in a slab cell and submitted to a magnetic field perpendicular to the slab plane, it organizes into a regular array of columns with micron-sized spacing. DNA migrating in this maze leads to size-fractionation. Resolution of lambda phage (48.5 kbp) and T4 (140 kbp) DNA molecules in 30 mn is achieved. The motion of individual DNA molecules during FAE is observed using fluorescence videomicroscopy, and the molecular mechanisms responsible for separation are discussed in the light of recent computer simulations. During migration, large DNA molecules temporarily wrap around the impenetrable ferrofluid columns. They disengage by slippage, like a rope on a pulley, and the dependence of the disengagement time upon DNA size is responsible for the size-fractionation.