AFM images of the (SQ1A:SQ1B)
nanofiber. Left panel: The synapsable DNA nanofiber was prepared by dilution of purified SQ1A:SQ1B duplex originally diluted from 0.05 mol/L (50 mM) TMACl into 1 KMgTB buffer. The quadruplex sample was incubated for 12 h at 4°C prior to depositing it on the silicon wafer for imaging. The average height of the nanofiber is 0.45 ± 0.04 nm. Right panel: Gel-purified SQ1A:SQ1B duplex was heated to 90°C for 5 min and kept at 50°C for 72 h. The concentration was 6.7 × 10−9 mol/L (6.7 nM) quadruplex. A drop of sample was placed on the silicon wafer substrate, evaporated for 10 min at room temperature, and then washed with purified water three times prior to drying at room temperature for 1 to 2 h. Average height above the background of the bundles is 0.9 ± 0.4 nm.