Collapse of the protein homeostasis (proteostasis) can lead to accumulation and aggregation of unfolded proteins, which has been found to associate with a number of disease conditions including neurodegenerative diseases, diabetes and inflammation. Here we report a maleimide‐functionalized tetraphenylethene (TPE)‐derivatized fluorescent dye, TPE‐NMI, which shows fluorescence turn‐on property upon reacting with unfolded proteins in vitro and in live cells under proteostatic stress conditions. The level of unfolded proteins can be measured by flow cytometry and visualized with confocal microscopy.

Fluorescent dyes with aggregation-induced emission (AIE) properties exhibit intensified emission upon aggregation. They are promising candidates to study biomolecules and cellular changes in aqueous environments when aggregation formation occurs. Here, we report a group of 9-position functionalized anthracene derivatives that were conveniently synthesized by the palladium-catalyzed Heck reaction. Using fluorometric analyses, these dyes were confirmed to show AIE behavior upon forming aggregates at high concentrations, in viscous solvents, and when poorly solubilized. Their photophysical properties were then further correlated with their structural features, using density functional theory (DFT) calculation. Finally, we demonstrated their potential applications in monitoring pH changes, quantifying globular proteins, as well as cell imaging with confocal microscopy.

Collapse of proteostasis has been found in a number of disease conditions including neurodegeneration, diabetes and inflammation. To assess protein unfoldedness as a measure of proteostasis capacity, a maleimide‐functionalized tetraphenylethene, TPE‐NMI, was synthesized which shows fluorescence turn‐on property upon reacting with unfolded proteins in vitro and in live cells under proteostatic stress conditions. The level of unfolded proteins can be measured by using flow cytometry and visualized with confocal microscopy. More information can be found in the Full Paper by Yuning Hong et al. on page 904 in Issue 6, 2019 (DOI: 10.1002/asia.201900150).