Dual-monitoring Glycosylation and Local pH in Live Cells by Metabolic Oligosaccharide Engineering with a Ratiometric Fluorescent Tag.

Glycosylation and local pH change play vital roles in many biological processes. Monitoring the distribution of glycosylated molecules and their local nanoenvironment pH in live cells would provide deep insights into cellular metabolism. In this paper, we have reported a new cyclooctyne-linked fluorescent tag, ANCO, which can freely diffuse into cells and selectively label azide-modified glycans by a bioorthogonal copper-free click reaction. Combining with metabolic oligosaccharide engineering, ANCO could help to visualize the dynamic distribution of glycans as well as their local pH by ratiometric fluorescence signals. Using this strategy, we simultaneously observed the glycosylation inhibition and the local pH change of glycans in live cells after treatment with tunicamycin, a glycosylation inhibitor. ANCO showed great promise as a universal tool for dual-monitoring the distribution of azido-metabolic molecules and their local nanoenvironment pH in live cells.