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. Author manuscript; available in PMC: 2019 Feb 20.
Published in final edited form as: Nat Methods. 2018 Aug 20;15(9):685–688. doi: 10.1038/s41592-018-0105-0

Figure 1. SOMAmers as labeling probes for quantitative, high resolution DNA-PAINT imaging of membrane receptors.

Figure 1

(a) Labeling scheme using SOMAmers for diffraction-limited imaging with a fixed dye. (b) Labeling scheme using SOMAmers for DNA-PAINT super-resolution imaging. Transient binding of a dye-labeled strand to a complementary docking strand is enabled by single-stranded extension of the SOMAmer sequence. (c) SOMAmer against EGFR labeled with a fixed Cy3 dye (SL1069, see scheme in a) allows specific detection of EGFR in A549 cells using confocal microscopy. (d) Diffraction-limited DNA-PAINT image using a complementary dye-labeled imager strand against a docking-site-modified SOMAmer (see scheme in b) against EGFR (standard deviation image) in A431 cells. (e) Zoom-in of highlighted area in the diffraction-limited image in d. (f) Corresponding DNA-PAINT super-resolution image of the highlighted area in d. (g, top) Zoom-ins of highlighted areas (i, ii, and iii) in f. (g, bottom) Cross-sectional histogram analysis in i, and iii, respectively, demonstrates high-resolution DNA-PAINT imaging of single EGFR proteins labeled using SOMAmers. (h) Fitting a Gaussian distribution to the center-of-mass-aligned single-molecule localizations of ~34000 SOMAmer-labeled EGFR proteins yields a localization precision of 3.2 nm. (i) qPAINT analysis of single EGFR proteins yields a unimodal distribution of binding events, confirming quantitative 1:1 labeling of EGFR proteins using SOMAmers. Scale bars: 10 µm (c), 2 µm (d), 200 nm (e, f), 20 nm (g). Experiments were repeated at least three times with similar results; representative data are shown.