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. Author manuscript; available in PMC: 2021 Mar 30.
Published in final edited form as: Nat Chem. 2020 Jul 20;12(9):832–837. doi: 10.1038/s41557-020-0506-4

Figure 2. Single-molecule fluorescence imaging of G-quadruplexes in living cells using the fluorescent probe SiR-PyPDS (1).

Figure 2

(a) Schematic of G4s in the cell nucleus with a zoom-in showing G4s stained by SiR-PyPDS (1). (b) Representative background-subtracted image (max projection of 100 frames with 200 ms exposure) of SiR-PyPDS (1) binding events in a living U2OS cell treated with 20 nM SiR-PyPDS (1) for 30 min before imaging; fluorescent puncta indicate binding of single SiR-PyPDS (1) molecules. Blue color corresponds to nuclear staining with Hoechst 33342. Scale bar is 2 μm. Inset scale bar is 1 μm. (c) Representative image of SiR-iPyPDS (2) staining in living U2OS cell treated with 20 nM SiR-PyPDS (1) for 30 min before imaging. Experiments b-c were repeated 3 times independently with similar results. (d) Quantification of the binding events within the nucleus lasting more than one frame (100 ms per frame) per cell for SiR-PyPDS (1) and SiR-iPyPDS (2). Center lines indicate the median; boxes show interquartile range; whiskers denote 5th and 95th percentiles. *** P = 3.5×10-7, two-sided Mann-Whitney U-test, n = 18 measurements from 6 cells each time in 3 independent replicates.