Synthesis Of Novel Fluorescence Probes And Study Of The Interaction Between The Probes And Biomolecules

In recent years, fluorescence assay is developed to a powerful analytical technique because of its high sensitivity and easy operation. Therefore, designing and synthesizing different kinds of fluorescent receptors have become a hot topic in this field. The fluorescent receptor usually consists of two parts, a recognizing moiety and a signal-report moiety. When the guest is bound with the recognizing moiety, the fluorescence properties of the receptor will undergo changes. The change of fluorescence spectrum can be used to recognize and sense the guest. We designed and synthesized three kind of compounds, studied the interactions between them or their metal complex and DNA or BSA. This thesis consists of four chapters.In chapter 1, the development of studing the interactions of small molecules and biomolecules has been elaborated since 2005.In chapter 2, a new Schiff-base compound, N'-(2-hydroxynaphthalenem-ethylene)-4-(2-hydroxylnaphthalenemethylenamine) benzoylhydrazine (1) was synthesized and the product was characterised by 1H NMR spectrum, Mass data and IR spectrum. The interaction between zinc complex (1-Zn) and bovine serum albumin (BSA) was investigated by fluorescence and absorption spectroscopies. A marked increase in the fluorescence intensity of 1-Zn was observed at 475 nm upon addition of BSA when excitation wavelength was set at 370 nm in pH 7.4 Tris-HCl buffer solution. Reversely, the intrinsic fluorescence of BSA could be quenched by 1-Zn complex. The quenching mechanism was suggested as static quenching according to the Stern-volmer equation and the UV-vis absorption spectral changes of 1-Zn upon addition of BSA. The binding constants Kb and the number of binding sites n were calculated. The effect of 1-Zn on the conformation of BSA was studied using synchronous fluorescence spectroscopy and three-dimensional fluorescence spectroscopy. In addition, the binding average distance r between the donor (BSA) and acceptor (1-Zn) was estimated based on the Forster's non-radiation energy transfer theory.In chapter 3, another Schiff-base compound,p-amino acetophenone- p- dimethylamino benzoyl hydrazone (2) was synthesized and and the product was characterised by 1H NMR spectrum. the interaction between 2 and calf thymus deoxyribonucleic acid (ct-DNA) was investigated by fluorescence and absorption spectroscopies. A significant increase in the fluorescence intensity of 2 was observed upon addition of ct-DNA in pH 7.4 Tris-HCl buffer solution when exited at 345 nm. The ionic strength experiment revealed that there was no electrostatic interaction between 2 and ct-DNA. The absorption titration of 2 with ct-DNA showed hypochromic effect. Study of interaction between 2 and denatured ct-DNA and 2 quenching the fluorescence of EB-DNA both revealed that the interaction mode between 2 and ct-DNA was intercalation interaction.In chapter 4, the interaction between zinc complex of 2-[2-(3,5-bis(2-pyridylmethyl)aminomethyl-4-hydroxy-phenyl)ethylene]-5-methylpyrazine (3) and ct-DNA was studied by fluorescence and absorption spectral assay. A notable increase in the fluorescence intensity of 3-Zn was observed upon addition of ct-DNA in pH 7.4 Tris-HCl buffer solution. The absorption titration of 3-Zn with ct-DNA showed no bathochromic shift and hypochromic effect. No anisotropy increase was observed when ct-DNA was added to 3-Zn solution. They both proved the lack of intercalation interaction between 3-Zn and ct-DNA. The ionic strength experiment, Scatchard plot, study of interaction between 3-Zn and denatured ct-DNA all revealed that the interaction mode between 3-Zn and ct-DNA was electrostatic interaction. Binding constant was calculated to be 7.96×104 L·moL-1.