a, Agarose gel electrophoreses showing the dimerization yields of the 40-nm and 60-nm wide DNA channels at different MgCl2 concentrations. Channel (dimer) bands are denoted by asterisks. The experiment was repeated three times with similar results. b, Different sizes of DNA channels purified by rate-zonal centrifugation. Agarose gel (1.5%) electrophoreses show the enrichment of DNA channel in fractions 11–13 (40 nm), 9–10 (60 nm), and 10–12 (45 nm), respectively. Well-folded nanostructure bands are denoted by asterisks. This experiment was repeated three times with similar results.