Carbohydrate Tethered Cyanostilbene Fluorogen: Unique Emission and Preferential Protein Binding

A simple and efficient construction of a water-soluble glycoconjugate bearing a cyanostilbene with glucose pendant and its interaction with proteins is reported. The absorption and fluorescence behavior of this glycoconjugate was investigated in organic solvents, binary-solvent mixtures, water and in the presence of proteins, concanavalin A, bovine serum albumin (BSA) and human serum albumin (HSA). With increase in the solvent polarity, the synthesized derivative exhibited emission quenching but in dioxane-pentane binary mixture, a significant red-shifted emission with substantial Stokes’ shift was observed. This emission response is attributed to the formation of aggregates and the results were substantiated by scanning electron microscopy (SEM) and dynamic light scattering (DLS) analysis. In the presence of proteins, the fluorophore exhibits moderate binding efficiency and shows synergistic interactions with a combination of hydrophobic and hydrophilic interactions. Circular Dichroism (CD) studies with protein and the fluorophore reveals changes in ellipticity confirming the binding of the fluorophore within the protein domains.