Fig. 1: Design and dimensions of the DNA leaf-spring nanoengine.
From: A rhythmically pulsing leaf-spring DNA-origami nanoengine that drives a passive follower
a, Schematic of the leaf-spring nanoengine, showing the dimensions of the stiff origami arms. Green circles, attachment sites for streptavidin binding; blue circle, T7RNAP part of the HT–T7RNAP fusion protein. Top: arrangement and dimensions of the 18-helix bundle that forms the origami arms. b, Schematic of the 90° left turn of the view shown in a. Orange rectangle, HT; blue circle, T7RNAP. c, Schematic and dimensions of the 90° left turn of the view shown in b. d, Schematic and dimensions of the 90° left turn of the view shown in c. e, Schematic and dimensions of the inner surface of the origami arms flanking the 28-nm-long leaf-spring helices (dark grey) that are arranged in a sliced honeycomb lattice fashion (below). Red dots, attachment sites of the dsDNA template strand; yellow dot, attachment site of the HT–T7RNAP. f, AFM characterization of the leaf-spring nanoengine. Overview (left) and detailed image (right) of the nanoengines. g, TEM of the nanoengine in negative staining. Overview (left) and detailed image (right) of the nanoengines. Green arrows, streptavidin molecules bound to biotin-modified staples protruding from one of the origami arms opposite to the location of the HT–T7RNAP fusion protein (blue arrow). h, Full opening and closing cycle of the compliant mechanical structure: (1) in the open structure the dsDNA template is bound by the immobilized HT–T7RNAP fusion protein and transcription begins; (2) upon transcription, HT–T7RNAP pulls the opposing origami arm towards itself, forcing the structure to close; (3) when the terminator sequence is reached, the T7RNAP releases the dsDNA template linker, which causes the structure to actively open to its equilibrium conformation. The T7RNAP can initiate the next closing cycle. i, Example of the nanoengine engaged in transcription. Blue arrow, HT–T7RNAP; green arrows, streptavidin. j, Example of the nanoengine engaged in transcription. Blue arrow, HT–T7RNAP; green arrows, streptavidin. All scale bars, 100 nm.
