M13mp18 scaffold

Unmodified DNA oligonucleotides were purchased from Integrated DNA Technologies. Fluorescently modified DNA oligonucleotides were purchased from Biosynthesis. Biotinylated monoclonal antibodies against β-tubulin and COX IV were purchased from Cell Signaling. Anti-PMP70 was purchased from Abcam. Anti-TGN46 was purchased from VWR. Streptavidin was purchased from Invitrogen (Catalog number: S-888). Bovine serum albumin (BSA), and BSA-biotin was obtained from Sigma Aldrich (Catalog Number: A8549). Glass slides and coverslips were purchased from VWR. Lab-Tek II chambered cover glass were purchased from Thermo Fisher Scientific. M13mp18 scaffold was obtained from New England Biolabs. p8064 scaffold for microtubule-like DNA origami structures was prepared as described before^{19 (link)}. ‘Freeze N Squeeze’ columns were ordered from Bio-Rad. TetraSpeck Beads were purchased from Life Technologies. Paraformaldehyde, glutaraldehyde and TEM grids (FORMVAR 400 Mesh Copper Grids) were obtained from Electron Microscopy Sciences.
Three buffers were used for sample preparation and imaging: Buffer A (10 mM Tris-HCl, 100 mM NaCl, 0.05 % Tween-20, pH 7.5), buffer B (5 mM Tris-HCl, 10 mM MgCl₂, 1 mM EDTA, 0.05 % Tween-20, pH 8), and buffer C (1×PBS, 500 mM NaCl, pH 8).

Ten nM of the M13mp18 scaffold
(New England Biolabs) was mixed with 100 nM of the 179 staples and
annealed for 23 h in 40 mM Tris-HCl, 45 mM boric acid, 1 mM EDTA,
14 mM MgCl₂, pH 8.2 using a protocol described previously.^{29 (link)}