title: Chemical and photophysical mechanism of fluorescence enhancement of 3-quinolineboronic acid upon change of pH and binding with carbohydrates.
abstract: The free 3-quinolineboronic acid (3-QBA) with the lowest (n-π*) excited singlet is non- or weakly fluorescent while protonated 3-QBA has the lowest (π-π*) excited singlet state and is highly fluorescent. The hybridization of boronic atom or charge transfer from aromatic ring to boronic acid group plays a secondary role in affecting fluorescence intensity. Binding with carbohydrate at a proper acidity, the hybridization of boron atom changes from sp(2) to sp(3) and the nitrogen atom in the quinoline ring is partially protonated, resulting in large enhancement of fluorescence. Meanwhile, the fluorescent lifetime of 3-QBA produces obvious change by binding with carbohydrates. Quinoline boronic acid is an important water-soluble fluorescence sensor for carbohydrate recognition. Both the remarkable changes in intensity and lifetime of 3-QBA can act as working parameters in recognition of carbohydrates at physiological pH.
authors.affiliation: College of Chemistry, Beijing Normal University, Beijing 100875, People's Republic of China.
authors.forename: Qian Jin
authors.initials: QJ
authors.lastname: Shen
authors.forename: Wei Jun
authors.initials: WJ
authors.lastname: Jin
mesh_terms: D001897:Boronic Acids / Q000737:chemistry*; D002241:Carbohydrates / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D013050:Spectrometry, Fluorescence
chemical_list: D001897:Boronic Acids; D002241:Carbohydrates