Thermodynamic Study On The Interaction Of Polyphenols And Bisphenol Compounds With Proteins

The widespread application of endocrine disruptors has caused great harm to human health.This result has aroused great concern from the people.In addition to anti-cancer,anti-oxidation,anti-thrombosis and prevention of heart disease,polyphenols are also used as food additives.By studying the interaction of polyphenolic compounds and endocrine disruptors with proteins at different temperatures,the results can be used to determine the binding mechanism between ligands and proteins.These data can provide useful information to mitigate the effects of endocrine disruptors on the human body and address some food safety issues.Combined with the actual situation of our laboratory on the basis of literature review,various spectroscopic methods combined with isothermal titration calorimetry(ITC),differential scanning calorimeter(DSC)and molecular docking were used to study the interactions between the competitive system of bisphenol F and polyphenols and various proteins at different temperatures levels.This paper is divided into the following four parts:The first part: The competitive interactions of piceatannol and bisphenol F with pepsin at different temperatures were studied by ITC,fluorescence spectroscopy,and circular dichroism spectrum.The effects of temperature on thermodynamic parameters were studied to determine the binding mode of the two ligands and observe the conformational changes of pepsin.The results showed that the binding ability between piceatannol and pepsin was superior to that of bisphenol F.Molecular docking results indicated that both piceatannol and bisphenol F can enter the active pocket of pepsin.The test results of the enzyme activity showed that the two ligands have an inhibitory effect on the activity of pepsin.The second part: Fluorescence spectroscopy study shows the binding mechanism of piceatannol and bisphenol F with human serum albumin at different temperatures.Fluorescence spectra and UV-visible absorption spectroscopy results indicate that the binding process is static quenching.The circular dichroism spectroscopy was used to study the conformational changes before and after protein-drug binding.The stability of the protein was determined by differential scanning calorimetry.The molecular docking technique was used to obtain information on the binding of the two ligands to the IIA site of human serum albumin and demonstrated that the two ligands were competitive with the binding of protein.The third part: The interactions between piceatannol or oxyresveratrol and trypsin at different temperatures were studied by fluorescence spectroscopy to obtain the binding mode and thermodynamic parameters.Differential scanning calorimetry and circular dichroism spectroscopy data showed that the stability and secondary structure of protein were altered.Through the molecular docking technology and enzyme activity assay,two polyphenolic compounds were found to interact with catalytically active amino acids of trypsin,resulting in inhibition of trypsin activity.The fourth part: The combination of fluorescence spectra and UV-visible absorption spectroscopy to obtain the binding of piceatannol or oxyresveratrol and lysozyme was static quenching process.Hydrogen bonding and van der Waals force were the main forces.Circular dichroism spectroscopy was used to study the effects of piceatannol and oxyresveratrol on the secondary structure of the enzyme.The binding sites of the two ligands to lysozyme can be obtained by molecular docking techniques.This result can be mutually verified with the results of the enzyme activity assay.