Study Of Interaction Between Protein And Small Molecules By Molecular Spectroscopy And Isothermal Titration Calorimetry

The study of the binding between proteins and small molecules has always been a hot spot.When small molecules enter the organism,they will be distributed through the intracellular specific transport system,thus interacting with proteins and affecting various physiological functions in the body.At present,many proteins have become the drug targets of certain diseases.Therefore,understanding the interaction between some compounds and proteins is very important for studying their pharmacological behaviors.And it is helpful to screen out small molecules that specifically bind to proteins,which provides a theoretical basis for the development and design of new drugs.In this thesis,the interactions of 3-phenyl-1H-indazole,pyrazole derivatives,flavonoids,ginsenoside F1 and chlorogenic acid with proteins were studied by isothermal titration calorimetry,spectroscopy and molecular simulation techniques.The research content of the thesis is divided into six parts.In the first chapter,the structure and function of five proteins are summarized,and the methods and contents of the interaction between proteins and small molecules are introduced.In the chapter two,in order to test whether there is specificity for the interaction between FTO(fat mass and obesity-associated)and 3-phenyl-1H-indazole,the interactions between 3-phenyl-1H-indazole and other four important proteins(human serum albumin,pepsin,catalase and trypsin)were investigated by isothermal titration calorimetry,spectroscopy and molecular docking methods.Calorimetry results showed spontaneously exothermic reactions occurred between 3-phenyl-1H-indazole and the proteins except trypsin under investigated conditions.The order of the binding affinity of 3-phenyl-1H-indazole is catalase > human serum albumin > FTO >pepsin.The interaction between the protein and 3-phenyl-1H-indazole is primarily hydrophobic.Spectroscopic results show that 3-phenyl-1H-indazole has an effect on the conformation of the five proteins.In the third chapter,the interaction between seven pyrazole derivatives(3a-3g)and human serum proteins(HSA)was studied by spectroscopy and molecular docking techniques.The results showed that all seven compounds can produce static quenching of HSA.Due to steric hindrance,3c has the greatest binding capacity to HSA.The interaction of these derivatives with HSA is mainly hydrogen bonding and hydrophobic interaction.In the fourth chapter,human serum albumin and three flavonoids(quercetin,liquiritin and taxifolin)were studied.The effects of three flavonoids on HSA were static quenching.Both calorimetry and fluorescence spectroscopy indicated that the binding constant of quercitrin and HSA was the largest.The interaction between HSA and quercitrin and liquiritin is hydrophobic and hydrogen bonding,while hydrogen bonding and electrostatic interaction dominate the binding of taxifolin to HSA.In the fifth chapter,the interaction mechanisms of ginsenoside F1 on three proteins(human serum albumin,trypsin and pepsin)were investigated.The results have shown that the binding ability of ginsenoside F1 to protein is weak,and a new complex could be formed.The order of strength is trypsin > pepsin > human serum albumin.The interaction between the three proteins and ginsenoside F1 is hydrophobic and hydrogen bonding.In the sixth chapter,the interaction between chlorogenic acid and three proteins(human serum albumin,trypsin and pepsin)was studied.The spectroscopy proves that chlorogenic acid is static quenching for three proteins.Calorimetry indicates the binding of chlorogenic acid to the three proteins is driven by entropy,and the binding force is human serum protein > trypsin > pepsin.In addition,hydrophobic interactions and hydrogen bonding play a major role in the binding of chlorogenic acid to the three proteins.