Transfection efficiency of siRNA in relation to concentration. Final concentration of small interfering RNA (siRNA) in culture media in nanomoles/litre (nM). Histograph analysis of flow cytometry data shows the transfection efficiency of siRNA. The darker peak represents the fluorescence-positive cell population, which is clearly shifted from the position of the gated untransfected cells (lighter peaks). Upper univariate range indicates proportion of fluorescent cells. These data are representative of two independent experiments.