V1 afm mica

To avoid the possibility of unintended deformation or change of mechanical properties of the DNA origami structures induced by EtBr intercalation and mechanical damaging during gel electrophoresis, only unpurified samples were used in AFM measurement. One microlitre of annealed sample was diluted using 19 μl of folding solution (1 × TAE, 20 mM MgCl₂), and deposited on a freshly cleaved mica substrate (highest grade V1 AFM Mica, Ted-Pella Inc.). After incubation for 5 min, the substrate was washed with DI water and gently dried by N₂ gun for 1 min. AFM images were taken by NX10 (Park Systems) using non-contact mode in SmartScan software. A PPP-NCHR probe having spring constant of 42 N m⁻¹ was used in the measurements (Nanosensors). Measured images were flattened with linear and quadratic order using XEI 4.1.0 program (Park Systems). Structural folding yield analysis and included angle measurement of DNA origami monomer structures from AFM images were done by custom scripts using MATLAB R2015b software (MathWorks Inc.). Typically, more than 250 monomer structures obtained from at least two different AFM images were used for each case.