Characterization Of The Interaction Between Environmental Endocrine Disrupting Chemicals With Biomacromolecule

Environmental endocrine disrupting chemicals （EDCs） is a kind of chemicalpollutant that can simulate or disturb normal hormone endocrine function, chargehormonal balance, effect on endocrine system in body. It has become a significantlyworldwide environmental problem because of its great hazardous nature, covert actionand widely influence. Its poisonous mechanism has become favorable research object inarea of environmental science, biology and toxicology, and so on.In this thesis, the interactions of hexythiazox, paclobutrazol, uniconazole anddiethylstilbestrol with human serum albumin were investigated by molecular dockingand spectroscopic approach. The interaction of imazethapyr with DNA was studieddetailedly using spectral probe. Moreover, their model and mechanism of interaction isdiscussed. Based on combining with theoretical predictions and experimentation, thetheoretical predictions are confirmed by experiments. These studies contributed torecognizing the EDCs’ harmfulness in molecular level. This thesis consists of sixchapters and the main contents are summarized as follows:1. The interaction of human serum albumin （HSA） with hexythiazox （HEX） waspredicted by molecular docking technique. Subsequently, the binding interaction undersimulative physiological conditions was preliminarily studied by UV-vis absorptionspectrometry. Moreover, the binding of HEX with HSA had been investigated bysynchronous fluorescence spectrometry, three-dimensional fluorescence spectroscopy.On the other hand, the features of HEX leading to conformational change of HSA havebeen explored. The binding constants and binding distance were calculated. Theinteraction forces and binding site were elucidated according to the thermodynamicparameters, number of the binding sites combining with the result of molecular docking. 2. The interactions of HSA with two kinds of plant-growth regulators paclobutrazol（PAC） and uniconazole （UNI） were predicted by molecular docking technique,respectively. The predicted results were consistent with those by UV-vis absorptionspectrometry under simulative physiological conditions. Subsequently, the results offluorescence spectroscopy, three-dimensional （3D） fluorescence spectra and circulardichroism （CD） spectroscopy suggested that PAC had a strong ability to quench theintrinsic fluorescence of HSA through static quenching procedure. Binding affinity （KA）and the amounts of binding sites （n） between PAC and HSA at291K were estimated as2.369×10⁵mol·L^-1 and1.357respectively, which confirmed that PAC could bind onboth site I and site II. An apparent distance between the Trp214and PAC was4.41nm.Additionally, PAC led to decrease in the α-helix structure and change in the peptidechain structure and surrounding microenvironment of HSA.3. The binding between diethylstilbestrol （DES） and HSA was investigated byUV-vis absorption spectrometry, fluorescence spectroscopy combining with moleculardocking. The binding constants, number of the binding sites and binding distance werecalculated. The thermodynamic analysis proved the binding behavior was mainlygoverned by hydrogen bond and van der Waals force. Furthermore, as evidenced by sitemarker experiments using two probe compounds, it revealed that DES acted on site Iand site II of HSA. Additionally, the effect of DES on the conformation of HSA wasinvestigated by synchronous fluorescence spectra and three-dimensional fluorescencespectra.4. The interactions of imazethapyr （IMA） and2-（4-methoxyphenyl）-ethenyl-naphthalenethiazole （MNT） with DNA were investigated in simulated physiologicalbuffer （pH7.4） using the ethidium bromide （EB） as a spectral probe by UV-visabsorption and fluorescence spectroscopy. The binding affinity （KA） of IMA and DNAwas calculated by a double reciprocal method, and the interaction forces wereelucidated according to the thermodynamic parameters. Interaction model between IMAand DNA was demonstrated by melting temperature （Tm）. Subsequently, the interactionmechanism between IMA and DNA is studied using MNT as a new probe.