Figure 4: Comparison of confocal and STED imaging of HeLa cells stained with SiR-Hoechst.
From: SiR–Hoechst is a far-red DNA stain for live-cell nanoscopy
(a) Confocal and (b) STED images of living HeLa cell nuclei stained with 4 μM SiR-Hoechst for 2 h in phenol red-free medium. Both confocal and STED images were slightly smoothed. A part of the background in the STED image is caused by a weak but non-negligible two-photon excitation of Hoechst by the 775 nm STED beam. Scale bars, 1 μm. On the right, close-ups of the regions indicated with a box. (c) Examples of normalized fluorescence intensity profiles obtained in the regions indicated by the arrows in b. Profiles from the raw STED images were fitted to Gaussian distributions. Number corresponds to single measurement of full width at half maximum of the fitted peak.
