Localization of siRNA. Huh7.5 cells were transfected with Cy5 labeled Cap siRNA using the lipid TKO reagent (middle panels) or by electroporation (right panels). Eighteen hours later, cells were collected and analyzed for Cy5 fluorescence by (A) flow cytometry or (B) fluorescence microscopy as described in Materials and Methods. Arrows denote the position of the nucleus. The gain in the Cy5 micrograph of electroporated cells was increased to compensate for lower levels of intracellular siRNA as compared to lipid-transfected samples.