Boronolectin with divergent fluorescent response specific for free sialic acid

摘要

A fluorescent boronate receptor with a unique response to free sialic acid has been developed; this divergent response system may find use in design of other fluorophores to discriminate between structurally similar analytes.rnBoronic acid-based carbohydrate sensors have been developed for a variety of biological applications from blood glucose monitoring, including glucose-responsive contact lenses, to "boronolectins" for cell-surface carbohydrate identification. The reversible esterification of boronates by carbohydrates in aqueous solution can be sensitively monitored either by fluorescence quenching, as first demonstrated by Czarnik, or through fluorescence signal increase by elimination of internal quenching mechanisms such as photon-induced electron transfer (PET), as first reported by Shinkai. Recently, James has developed an aniline-based system (1) that responds to monosaccharide binding with fluorescence signal enhancement via both locally excited (LE) and twisted internal charge transfer (TICT) states. The binding of sugar diols by the boron effectively turns fluorescence "on", i.e. there is an increase in fluorescence intensity (I> I_0). In order to compete with natural lectins for carbohydrate identification, boronolectins that are highly selective for particular monosaccharide ligands must be developed.