Agarose gel electrophoresis of poly(NLS)/DNA polyplexes. Samples containing 0.4 μg DNA were run on a 0.8% agarose gel and DNA was stained with ethidium bromide and visualized under UV illumination. Lane 1, DNA ladder; lanes 2–4, DNA treated with 0.1, 0.2 and 0.4 M NaCl; lanes 5–8, polyplexes incubated in the absence of DTT followed by treatment with 0, 0.1, 0.2, and 0.4 M NaCl; lanes 9–12, polyplexes incubated in 20 mM DTT followed by treatment as indicated in lanes 5–8.