Fig. 4: DNA origami-based platform for spacing control of TCR and CD4.

a Schematic of “surrogate” T cell – magnetic bead bearing 10 HB origami functionalized with precisely spaced TCR and CD4. b Schematic of micropipette adhesion frequency assay combined with ligand presentation by origami. c 10 HB origami controls separation distance of TCR and CD4 and attaches to magnetic bead via DNA strand hybridization. TCR binds to a streptavidin (SA), which also binds to a biotinylated DNA strand that hybridizes with a TCR-capturing DNA strand on 10HB origami. CD4 is covalently conjugated with a DNA stand that binds to a CD4-captruing strand. d Four distances were employed, with either 6, 13, 20, or 100 nm TCR–CD4 spacing. e SDS PAGE of CD4 conjugated to oligonucleotide for loading onto 10HB origami. f Native agarose gel electrophoresis of 10 HB origami with (1) no poly-A extensions or protein handles, (2) poly-A extensions but no protein handles, 3-6 poly-A extensions with protein handles spaced at 6, 13, 20, and 100 nm respectively. g TEM image of 10HB origami bearing CD4 and SA-coupled TCR with 13 nm (top) and 20 nm (bottom) spacing. Experiments in e and f were repeated three times. TEM images in g are representative of 30-50 images collected from samples prepared in three separate experiments. Source data are provided as a Source Data file.