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Epicocconone 1 is a natural chromophore isolated from the fungus Epicoccum nigrum that has shown applications in proteomics and fluorescent microscopy thanks to its unique pro‐fluorescence properties. The modification of the skeleton of the natural product by replacing the triene side chain by a fluorenyl scaffold can noticeably increase the fluorophore's absorption coefficient. The synthesis of the analogues of the natural product has been made possible by the use of a palladium‐catalyzed carbonylation reaction, allowing the construction of the β‐keto‐dioxinone key intermediate. Two‐photon absorption cross‐section measurements of the fluorenyl epicocconone analogues show a structure dependency with values ranging from 60 to 280 GM and live cell imaging show intense staining of intracellular vesicle‐like structures around the nucleus. [ABSTRACT FROM AUTHOR]

Cell Imaging Platforms (CIPs) are research infrastructures offering support to a number of scientific projects including the choice of adapted fluorescent probes for live cell imaging. What to detect in what type of sample and for how long is a major issue with fluorescent probes and, for this, the "hat-trick" "Probe–Sample–Instrument" (PSI) has to be considered. We propose here to deal with key points usually discussed in CIPs including the properties of fluorescent organic probes, the modality of cell labeling, and the best equipment to obtain appropriate spectral, spatial, and temporal resolution. New strategies in organic synthesis and click chemistry for accessing probes with enhanced photophysical characteristics and targeting abilities will also be addressed. Finally, methods for image processing will be described to optimize exploitation of fluorescence signals. [ABSTRACT FROM AUTHOR]

Identification of new fluorescent biomarkers is a key issue to decipher mechanisms in living cells. Isolated from the fungus Epicoccum nigrum , natural epicocconone (NE) establishes a covalent and reversible link with primary amines and has been identified as a new fluorescent dye for cell imaging. In the present study, the properties of a synthetic and multifunctional analogue of epicocconone (SE) have been compared to those of NE through 1-photon (1P) and 2-photon (2P) advanced light microscopies. 1P Λλ confocal microscopy analyses revealed that, in cell culture medium, SE and NE displayed two peaks of excitation (ex) at 480 and 530 nm and a large band of emission (em) with a maximum at 610 nm. In living cells, SE presented sharper bands compared to NE with maxima at 545 nm (ex) and 605 nm (em). In 2P microscopy, SE and NE presented maxima around 790 nm (ex) and 595 nm (em) when diluted in cell culture medium. In living cells, SE did not present any large disturbing blue-shift for emission that was observed for NE. In addition, 2P bands for SE were sharper than the NE ones. SE was 2–3 times more fluorescent than NE as determined through 1P and 2P approaches. SE did not induce any cytotoxicity and was adapted for time-lapse acquisition. In PC12 cells, SE broadly labeled nuclear and plasma membranes, vesicles-like structures and organelles including the Golgi apparatus and mitochondria. Taken together, these data indicate that SE has appropriate properties for in vitro and in vivo cell biology studies and presents many advantages compared to NE for 1P and 2P microscopies. [ABSTRACT FROM AUTHOR]