Environment-sensitive amphiphilic fluorophore for selective sensing of protein.

Here we report the selective sensing of BSA (bovine serum albumin) by 8-(alkoxy)quinoline-based fluorescent probes, via non-covalent interactions. The weak fluorescence of these probes in aqueous solution showed a dramatic increase in quantum yield and lifetime upon binding with BSA, while the responses to various other proteins/enzymes used were negligible under similar experimental conditions. The emission of the probe is affected by the interplay with BSA but not with tryptophan amino acid suggesting that the microenvironment created by the macromolecule induces some change in their excited-state properties. Binding site assignment by a known site-selective binding ligand enabled us to conclude that the compounds predominantly bind at site I of BSA. The changes in fluorescence intensity and the position of emission maxima of compounds in presence of BSA along with the increase in steady state anisotropy values well reflect the nature of binding and location of the probe inside the protein environment. Compounds interact with BSA efficiently and exhibit site selectivity and thus have the potentiality to serve as an efficient and selective sensor of protein.