Fluorophotometric Determination of Histone with 3,4,5,6-Tetrafluoro-2-carboxyphenylfluorone–Manganese(II) Complex and Its Characterization

A simple fluorophotometric method for the determination of histone has been developed. This method involves a fluorescence quenching reaction that results in the formation of a complex of manganese(II), 3,4,5,6-tetrafluoro-2-carboxyphenylfluorone (TFCPF), and histone in a non-ionic surfactant micellar medium. The calibration curve was found to be linear in the range of 0.5 to 2.0 µg/mL. The binding parameters (n, number of binding sites; K, binding constant) and thermodynamic parameters (ΔG0, change in Gibbs free energy; ΔH0, change in enthalpy; ΔS0, change in entropy) were investigated spectrophotometrically for the elucidation of the reaction mechanism. The resulting binding parameters (n=4.08 and K=3.16×104 m −1 at 25°C) and thermodynamic parameters (ΔG=−25.83 kJ/mol, ΔH=−9.83 kJ/mol, and ΔS=53.68 J/(mol K)) suggest that the colored complex in this reaction system is an ion-association complex between manganese(II)–TFCPF and histone.