title: Studies of the fluorescence light-up effect of amino-substituted benzo[b]quinolizinium derivatives in the presence of biomacromolecules.
abstract: A comparative study of the ability of amino-substituted benzo[b]quinolizinium derivatives to act as DNA- or protein-sensitive fluorescent probes is presented. Spectrophotometric titrations, DNA denaturation studies and viscometric titrations showed that all tested aminobenzo[b]quinolizinium derivatives intercalate into DNA with binding constants K(b) = 10(4)-10(5) M(-1). The intense fluorescence of the 9-aminobenzo[b]quinolizinium (Φ(fl) = 0.41) as well as the intrinsically very weak emission of the 7-aminobenzo[b]quinolizinium (Φ(fl) < 0.005) are quenched by the addition of DNA, most likely caused by a photoinduced electron transfer (PET) between the excited intercalated ligand and the DNA bases. The 6-aminobenzo[b]quinolizinium (1b) and the 6-amino-9-bromobenzo[b]quinolizinium (1c) exhibit very low fluorescence intensity in water (Φ(fl) < 0.005). However, in water-glycerol mixtures the emission intensity increases by factors of 56 (1b) and 27 (1c) with increasing glycerol content of the solution (0-100 wt%), which indicates the radiationless deactivation of the excited state of 1b and 1c due to a torsional relaxation, i.e. rotation about the exocyclic C(ar)-NH(2) bond. In the case of the bromo-substituted derivative 1c, a viscosity-independent heavy-atom-effect of the bromo substituent leads to additional quenching. The association of 1b and 1c with ds DNA leads to a restricted conformational flexibility of the intercalated ligand and results in an increase of fluorescence intensity. This effect is particularly strong in the presence of poly[dA-dT]-poly[dA-dT]. Upon association with ct DNA or poly[dG-dC]-poly[dG-dC] only very small enhancement of emission intensity (1b) or even a slight quenching (1c) of the fluorescence was observed because of the interfering PET reaction with the guanine residues. Preliminary experiments reveal that the 6-aminobenzo[b]quinolizinium derivatives 1b and 1c may also be employed as protein-sensitive probes, because their emission intensity increases upon association with selected albumins.
authors: University of Würzburg, Institute of Organic Chemistry, Am Hubland, 94047, Würzburg, Germany.
authors: Katja
authors: K
authors: Faulhaber
authors: Anton
authors: A
authors: Granzhan
authors: Heiko
authors: H
authors: Ihmels
authors: Daniela
authors: D
authors: Otto
authors: Laura
authors: L
authors: Thomas
authors: Sharon
authors: S
authors: Wells
mesh_terms: D000042:Absorption; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004579:Electron Transport; D005990:Glycerol / Q000737:chemistry; D007364:Intercalating Agents / Q000737:chemistry*; D011067:Poly dA-dT / Q000737:chemistry; D011506:Proteins / Q000737:chemistry / Q000378:metabolism; D011789:Quantum Theory; D011807:Quinolizines / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D014867:Water / Q000737:chemistry
chemical_list: D007364:Intercalating Agents; D011506:Proteins; D011807:Quinolizines; D014867:Water; D011067:Poly dA-dT; D004247:DNA; D005990:Glycerol