Red-Emitting Fluorophores with Tailored Properties for Microscopy and Nanoscopy

Abstract

Extended series of red-emitting rhodamine dyes were synthesized and tested. This revealed the real factors determining the quality of STED (stimulated emission depletion) imaging, dye photostability in general, and stability of the corresponding reactive labels. Previously overlooked and underestimated observations are now being highlighted and discussed. So are some very important syntheses-related aspects. The studies were also expanded on far-red emitting oxazine and silicon rhodamine dyes. An intriguing discovery emerged when certain fluorophores, which were originally designed for STED, demonstrated an ability to discern between viable and dead bacterial cells. Recent publications by Lucidi and co-workers showed that certain positively charged dyes allow imaging of bacterial membranes using both conventional techniques, for example, confocal laser scanning microscopy (CLSM), and STED. This opens avenues for investigating membrane biogenesis and diagnostics.