Development of sugar-based fluorescence (FL) chemo-probes is of much interest since sugars are biocompatible, water-soluble and structurally rigid natural starting materials. Researchers from Shanghai Institute of Materia Medica and East China University of Science and Technology reported a sugar-based fluorescent chemo-probe. 

Fluorescent glycoligands with two triazolylcoumarin moieties installed onto the different positions of an identical glucosyl nucleus exert completely reversed optical response to a metal ion. C3,4-, C2,3- and C4,6-di-substituted coumaringlucosides synthesized by a click reaction similarly showed a selective FL variation in the presence of silver (I) among a range of metal cations in an aqueous solution. 

However, the variation was determined to be converse: the FL of the C3,4-ligand was quenched whereas that of the C2,3/C4,6-ligand tangibly enhanced. FL and NMR titrations suggested that this divergence was due to the distinct complexation modes of the conformationally constrained ligands with the ion. The optimal motifs of the ligand-ion complexation were predicted by a computational simulation. Finally, the C2,3-ligand was determined to be of low cyto-toxicity and applicable in the FL imaging of silver ions internalized by live cells.  

This research work was performed by graduate student WEI Xiaoli and colleagues in LI Jia’s and CHEN Guorong’s groups. This study paves the way for the design and development of sugar-based fluorescent chemo-probes with tunable FL owing to the conformational constraint of fluorophore-receptor moieties modified on a rigid glycosylplatform. The research work has been recently published in Sci. Rep. ((IF 2.927) 2014, 4:4252).  

Substitution Pattern Reverses the Fluorescence Response of Coumarin Glycoligands upon Coordination with Silver (I) (Image by Prof. LI Jia ’s group)