Thermodynamic Study On The Interaction Between Anticancer Drug Synergistic System Of Catechins-pyrimidine And Protein

With the enhancement of the incidence of cancer and the increase of drug resistance,combination therapy has become an inevitable trend.The widely used pyrimidine drugs are faced with the problem of serious toxic side effects,however,catechins have the advantage of small side effects except for anticancer effect.After studying the interactions between anticancer drug synergistic system of catechins-pyrimidine and protein at different temperatures and pHs,the mechanism of the drugs and the relationship between the two drugs when they are coexisting can be obtained,and the study will provide a theoretical basis for clinical combination therapy.Combined with the actual situation of our laboratory on the basis of literature review,various spectroscopic methods combined with isothermal titration calorimetry(ITC)and molecular docking were used to study the interactions between the synergistic system of catechins-pyrimidine and human serum albumin(HSA)at different temperatures and pH levels.As a part of the National Natural Science Foundation(No.21473085),this paper is divided into the following four parts:The first part: To explore the influence of temperature and pH on the number of binding sites,binding constants,enthalpy changes,entropy changes,determine the mode of action of the two drugs simultaneously,and observe the conformational changes of protein,the competitive interactions of EGCG and FU with HSA at different temperatures and pHs were studied by ITC and fluorescence spectroscopy,circular dichroism spectrum,dynamic light scattering.The time resolved fluorescence spectra showed that the interactions of EGCG or FU with HSA were static quenching.The second part: The binding mechanisms of EGCG and TF with HSA at different temperatures and p Hs were investigated by ITC together with fluorescence spectroscopy,the static quenching process can be obtained by UV-Vis absorption spectra,the conformational changes of HSA before and after the interactions can be monitored by dynamic light scattering,circular dichroism spectrum and infrared spectrum.To further demonstrate the relationship between the the two drugs which are existed at the same time,the positions of the two drugs can be simulated by molecular docking.The third part: The interactions between ECG or TF and HSA at different temperatures and pHs were studied by ITC and fluorescence spectroscopy,then analyzed the mechanism of single drug and the advantages and disadvantages of combined drugs according to the data,the effect of temperature and pH also can be acquired.Dynamic light scattering and circular dichroism spectrum can explain the slightly changes in secondary structure of HSA.The fourth part: The thermodynamic parameters such as binding constants,the number of binding sites,enthalpy and entropy changes in the interactions between ECG or TF with HSA can be obtained by ITC and fluorescence spectroscopy,and the influence of combination therapy can be understanded by the comparision of the difference between single drug and the two drugs.The binding positions can be determined by molecular docking,other experiments were used to test the microenvironmental changes of the protein.Meanwhile,we compare the similarities and differences between the analogues.