Article,
Optical Sensing of Aromatic Amino Acids and Dipeptides by a Crown‐Ether‐Functionalized Perylene Bisimide Fluorophore
Chemistry - A European Journal, 24 (31): 8009-8016 (June 2018)
DOI: 10.1002/chem.201800870.
Abstract
The host–guest binding properties of a fluorescent perylene bisimide (PBI) receptor equipped with crown ether were studied in detail with a series of aromatic amino acids and dipeptides by UV/Vis, fluorescence and NMR spectroscopy. Fluorescence titration experiments showed that electron‐rich aromatic amino acids and dipeptides strongly quench the fluorescence of the electron‐poor PBI host molecule. Benesi–Hildebrand plots of fluorescence titration data confirmed the formation of host–guest complexes with 1:2 stoichiometry. Binding constants determined by global analysis of UV/Vis and fluorescence titration experiments revealed values between 103 m−1 and 105 m−1 in acetonitrile/methanol (9:1) at 23 °C. These data showed that amino acid l‐Trp having an indole group and dipeptides containing this amino acid bind to the PBI receptor more strongly than other amino acids and dipeptides investigated here. For dipeptides containing l‐Trp or l‐Tyr, the binding strength is dependent on the distance between the ammonium group and the aromatic unit of the amino acids and dipeptides leading to a strong sensitivity for Ala‐Trp dipeptide. 1D and 2D NMR experiments also corroborated 1:2 host–guest complexation and indicated formation of two diastereomeric species of host–guest complexes. The studies have shown that a properly functionalized PBI fluorophore functions as a molecular probe for the optical sensing of aromatic amino acids and dipeptides.
