Spm multimode with nanoscope 5 controller

AFM images were obtained using a SPM Multimode with Nanoscope V controller (Bruker). Normally 50 μl of 0.5× TE buffer with 15–20 mM MgCl₂ were applied to a freshly cleaved mica surface, and then a 5 μl droplet of a sample (2–10 nM) was added and incubated for ∼2 min. Supplementary 10–20 μl of 10 mM NiCl₂ was added to increase the strength of DNA-mica binding (30 (link)). Additional dilution of the sample was possibly performed to achieve the desired sample density. Samples were imaged under liquid ScanAsyst mode with C-type triangular tips (resonant frequency, = 40–75 kHz; spring constant, k = 0.24 N m⁻¹) from the SNL-10 silicon nitride cantilever chip (Bruker).

AFM images were obtained using a SPM Multimode with Nanoscope V controller (Bruker). Forty microliters of 0.5 × TE buffer with 10 mM MgCl₂ were applied to a freshly cleaved mica surface, and then a 5 μL droplet of purified sample (2–10 nM) was added and incubated for approximately 2 mins. Supplementary 10 μL of 10 mM NiCl₂ was added to increase the strength of DNA–mica binding^{47 (link)}. Additional dilution of the sample was possibly performed to achieve the desired sample density. Samples were imaged under liquid ScanAsyst mode, with C-type triangular tips (resonant frequency, f₀ = 40–75 kHz; spring constant, k = 0.24 N m⁻¹) from the SNL-10 silicon nitride cantilever chip (Bruker). Additional details of measurements based on AFM results can be found in Supplementary Information.