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Stimulated emission depletion (STED) nanoscopy allows observations of subcellular dynamics at the nanoscale. Applications have, however, been severely limited by the lack of a versatile STED-compatible two-colour labelling strategy for intracellular targets in living cells. Here we demonstrate a universal labelling method based on the organic, membrane-permeable dyes SiR and ATTO590 as Halo and SNAP substrates. SiR and ATTO590 constitute the first suitable dye pair for two-colour STED imaging in living cells below 50 nm resolution. We show applications with mitochondria, endoplasmic reticulum, plasma membrane and Golgi-localized proteins, and demonstrate continuous acquisition for up to 3 min at 2-s time resolution., The intracellular applications of STED microscopy are limited by the availability of dyes. Here the authors develop a two-colour labelling strategy based on SiR and ATTO590 dyes, and apply their strategy to image various subcellular membrane compartments.

NMR spectroscopic studies with a series of proline derivatives revealed that the polarity of the environment has a significant effect on the trans : cis isomer ratio of Xaa–Pro bonds. Computational studies showed that this effect is due to differences in the overall dipole moments of trans and cis conformers. Comparisons between the conformational properties of amide and ester derivatives revealed an intricate balance between polarity effects and n → π* interactions of adjacent carbonyl groups. The findings have important implications for protein folding and signaling as well as the performance of proline-based stereoselective catalysts., Chemical Science, 6 (12), ISSN:2041-6520, ISSN:2041-6539