Study On The Mechanism Of The Interactions Between Flavonoids Of Active-Constituents Of Medical Plants And DNA

Deoxyribonucleic acid(DNA) is an important genetic substance in organic. Exploring the interaction mechanisms on these bio-macromolecules with small molecules or ions,especially for those drug molecules,at the molecular level is of current hot subjects in many research areas such an biology,clinic medicine, medicinal chemistry,chemistry and so on.In this thesis,the binding modes between some flavonoids and its rare earth metal complexes with DNA were studied by uorescenee and UV-vis absorption spectrophotometry.The application of chemometries in analysis of two-dimensional data also had been developed,and it can solve some problems and obtain the equilibrium concentration and pure spectra of each component in complicated biochemical system(DNA-probe-small molecular). The conclusions of the thesis are summarized as follows:1.The chemical and biological characters of DNA were introduced simply first; And then the research methods,research objects and binding modes of interaction between small molecules and DNA were reviewed in turns.Moreover the research status of the interaction between flavonoids active components and its metal complexes and DNA were summarized recently;At last,the development trend was forecasted.2.The interaction between catechin and DNA in physiological condition(pH 7.4) was studied by fluorescence and UV absorption spectrophotometry.The results indicated the major mode of binding was intercalation binding of catechin with DNA through fluorescent probe(ethidium bromide),I^- fluorescence quenching effect,the melting point effect of DNA and salt effect.In addition,The binding constant and number of binding sites between catechin and DNA were calculated to be 9.44×10⁴ L·mol^-1 and 1.18,respectively,based on the intrinsic fluorescence quenching of catechin by DNA.3.The interaction of puerarin with DNA was studied by fluorescence and absorption spectrometric methods using neutral red as a spectral prob.Effect of ionic strength and I^- concentration on binding of puerarin with DNA were investigated.It is found that puerarin can react with DNA under physiological conditin(pH7.40).The major mode of recognition is groove binding between puerarin and DNA.The quenching belonged to static fluorescence quenching.The binding constant and binding site for querarin with DNA was 1.67×10⁵ L·mol^-1 and 1.19 respectively.4.The interaction between morin-Eu³⁺ complex and calf thymus DNA in physiological buffer(pH 7.4) was investigated by UV-vis spectrophotometry, fluorescence spectroscopy,viscosity measurements and DNA melting techniques.All the results suggested that morin-Eu³⁺ complex can bind to DNA,and the major binding mode is intercalation binding.The binding constants of morin-Eu³⁺ complex with DNA at 292 K,301K and 310K were calculated as 7.47×10⁴,8.89×10⁴ and 1.13×10⁵ L mol^-1,respectively.The thermodynamic parameters were obtained,which suggested that hydrophobic force plays a major role in the binding of morin-Eu³⁺ complex to DNA.5.The interaction of kaempferol with calf thymus DNA in physiological buffer (pH 7.4) was investigated by UV-vis spectrophotometry,synchronous fluorescence spectroscopy,viscosity measurements and DNA melting techniques,using the Neutral Red dye(NR) as a fluorescence probe of DNA.The results suggested that kaempferol can bind to DNA,and the major binding mode is intercalation binding.At the same time,it was proved that the quenching at different temperatures belonged to static fluorescence quenching between kaempferol and DNA.And then the binding constants,binding sites and the thermodynamic parameters were obtained.6.The interaction between kaempferol-Eu³⁺ and calf thymus DNA in physiological buffer(pH 7.4) was investigated by UV-vis spectrophotometry, synchronous fluorescence spectroscopy,viscosity measurements and DNA melting techniques,using the Neutral Red dye(NR) as a fluorescence probe of DNA.The results showed that both kaempferol-Eu³⁺ complex and NR molecule can intercalate into the double helix layer of DNA,and there was a competition between these two interactions.Information such as binding constants at various temperatues and thermodynamic parameters were obtained.Furthermore,a chemometrics approach, alternative least squares(ALS) algorithm,was used to resolve the measured complex two-way array absorption spectral data and the equilibrium concentration profiles of each component in the reaction as well as the corresponding pure spectra were obtained. The ALS analysis showed that the intercalation of kaempferol-Eu³⁺ complex molecule into DNA proceeds by exchanging with NR probe,and can be attributed to two parallel reactions.