Study On The Interaction Between Environmental Estrogens And DNA

Environmental Estrogens(EEs) is a kind of external chemical substance, which can disrupt the normal endocrine of human and animals, they can through the combined with estrogen receptors, competition the binding sites on the receptor binding, play the similar effect of estrogen and affect the cell signaling pathways. As an important carrier of organisms genetic material, DNA is one of the main targets of many small molecules, these small molecules may cause damage to the DNA molecule, and harm the growth of the organism. Therefore inord to provide theoretical basis, for further understanding the mechanism of action of environmental estrogen and DNA, the study of between the EEs and DNA is very important. In this paper, combined use of A variety of spectroscopy, chemometrics techniques, and the molecular simulation to simulate human physiological acidity(pH 7.4) condition,researched of the three kinds of environmental estrogens(diethylstilbestrol, bisphenol A, bisphenol AF) interaction with calf thymus DNA.The main contents of these investigations were summarized as follows:1. A brief introduction of the physiological characteristics of DNA and the main harm of environmental estrogens, introduction the basic theory and testing method about how to study the interaction of biological molecules and small molecules.2. Under the conditions in the human body physiological acidity(pH 7.4), with acridine orange(AO) as a fluorescence probe, using fluorescence spectrometry,circular dichroism(CD) and fourier transform infrared spectroscopy(FT–IR), and viscosity measurements, measured the interaction of environmental estrogen diethylstilbestrol(DES) with calf thymus DNA(ctDNA). Results showed that DES bound to A, T base pairs of ctDNA through intercalation, swap out the AO which before embedded into the ctDNA. The binding constant reached of 104, the thermodynamic parameter change value of enthalpy and entropy were both less than zero, explained the hydrogen bond and van der Waals force was the main drivingforce in the reaction. And the existenced of the DES also made the relative viscosity value of ctDNA increased, and leads to the conformation of ctDNA from B form changed to A form.3. In the buffer solution of Tris–HCl(pH = 7.4 Tris–HCl), combined with chemometrics multivariate curve resolution–alternating least squares(MCR–ALS),spectral measurement, DNA melting measure, viscosity measure and molecular simulation technology researched the binding properties between bisphenol A(BPA)and ctDNA. Found that BPA can embed into the spiral structure of ctDNA, made the melting and viscosity have a certain degree of increase. Measured the binding constant of reaction is 103. The researches of FT–IR and CD analysis showed that the main effected of BPA on ctDNA was A, T base pairs, and leaded to ctDNA conformation from B changed to A. Molecular simulation showed the spatial combination of BPA intercalation with ctDNA. Application of MCR–ALS analysis the ultraviolet absorption spectrum of BPA and ct DNA reaction, obtained in the reaction system(BPA, ctDNA, ct DNA–BPA) concentration change, it can been used to quantitative determination the interaction process of BPA and ctDNA. It was also found that with the added of β–cyclodextrin(β–CD), the fluorescence intensity of BPA markedly improved, the existence of β–CD provided a hydrophobic environment for BPA, and did not significantly influence the combination of BPA and ctDNA,4. MCR–ALS method used to parse the complex ultraviolet spectrum data matrix of bisphenol AF(BPAF) and ctDNA reaction, obtained the earch reaction components spectral curves and concentrations change trend, based on thes researches, which can realize the process monitoring of the BPAF interact with ctDNA. Fluorescence quenching experiments showed that ctDNA through static quenching mechanism to decrease the fluorescence intensitty of BPAF, the hydrophobic force and hydrogen bond controlde all reaction. BPAF mainly through intercalation mode combined with ctDNA, these conclusion consistent with KI experiment, DNA single and double chain experiment, ionic strength experiment,viscosity measurement. FT–IR and CD spectra researchs showed that BPAF mainly combination in G, C base pairs of ctDNA, and make ctDNA type B conformationbecame loose. Molecular simulation results depicted the three-dimensional combination mode of BPAF and ctDNA.