Frequency histograms showing the mean and variation of intracellular fluorescence 4 hours after SL-O and electroporation delivery of fluorescent ODN (20 μmol/L extracellular concentration) into KYO1 cells. (A) The filled grey area represents cells permeabilized with an optimal concentration of SL-O (data from Fig 3A). The solid line represents cells permeabilized with a supraoptimal concentration of SL-O (data taken from the experiment described in Fig3B). The grey line represents electroporated cells (data from Fig 3B). (B) The solid line represents electroporated cells. The grey line represents cells permeabilized with a suboptimal dose of SL-O, designed to give equivalent ODN loading (mean of 1.2 attomoles per cell).