Photocyclisation of Diphenylamine as a Fluorogenic Reaction for Photochemical‐Fluorimetric Analysis

Abstract

photometrically and spectrophotofluorometrically in several organic solvents at room temperature. A two-step photoreaction takes place, with the formation of carbazole as the main fluorescent photoproduct. In most solvents, the fluorescence intensity of diphenylamine is increased upon UV irradiation, reaching a maximum within 10 to 15 min. Photochemical-fluorescence enhancement factors range between 3 and 35. Linear log-log calibration plots are obtained over several orders of magnitude in concentration units. Photochemical-fluorimetric limits of detection are as low as 2 0 pg 1-1. The photocyclisation of diphenylamine is shown to be a very useful fluorogenic reaction for its quantitative analysis.The photocyclisation reaction of diphenylamine has been studied spectro- INTRODUCTIONRecently, photochemical fluorogenic reactions have been proposed for improving the sensitivity and selectivity of fluorimetric detection of naturally non-fluorescent or weakly fluorescent organic compounds in bulk liquid solution (1-9) as well in combination LIith HPLC or with TLC (10-23).In the present work, we have investigated the analytical usefulness of the photocyclisation reaction of diphenylamine (Scheme I) ( 2 4 -2 8 ) for the fluorimetric determination of this compound.

Comment on “Multiple Independent Binding Sites for Small-Molecule Inhibitors on the Oncoprotein c-Myc”

“…This involves Coulombic interaction between the electronically allowed π–π* transition moments of the chromophoric unit(s) of the guest compound and proximal aromatic side chains. − This type of coupling is referred to as nondegenerate because the coupled transitions are different in energy. The carbazole chromophore shows a strong absorption band around 250 nm ( 1 B a , ε max ∼ 28 000 M –1 cm –1 ). , Two opposite ICD signals appear in the CD spectrum corresponding to the absorption band of the ligand and the interacting residues, respectively. The latter one could not be observed due to the strong masking effect of the intrinsic CD contribution of the peptide/protein at lower wavelengths.…”

“…The carbazole chromophore shows a strong absorption band around 250 nm ( 1 B a , ε max ∼ 28 000 M −1 cm −1 ). 19,20 Two opposite ICD signals appear in the CD spectrum corresponding to the absorption band of the ligand and the interacting residues, respectively. The latter one could not be observed due to the strong masking effect of the intrinsic CD contribution of the peptide/protein at lower wavelengths.…”