Dose-dependent detection of siRNA transfection efficacy by immunofluorescence observation. The following doses of siRNA were assessed: A: 30 pmol/ml. B: 50 pmol/ml. C: 70 pmol/ml. D: 100 pmol/ml. By visual inspection of the fluorescence intensity and frequency of cells transfected, we selected a dose of 50 pmol/ml in subsequent experiments.