Study On The Interaction Of Theaflavin With Human Serum Albumin,Glycated Human Serum Albumin And Lactoferrin

Tea polyphenols—theaflavin have become the focus of attention for researchers in researching various antioxidants and treating various chronic diseases due to their high antioxidant activity and their unique properties to promote human health.The effects of theaflavin on the transporters in plasma after ingestion into the body and the structure and function of proteins in the coexisting food system are worthy of our attention.In this paper,firstly,the interaction mechanisms of theaflavin(TF1),theaflavin-3-gallate(TF2)and theaflavin-3,3'-disgallate(TFDG)with human serum protein(HSA)and glycated human serum protein(GHSA)were comparative studied by spectroscopic methods such as fluorescence spectroscopy,ultraviolet-visible absorption spectroscopy,circular dichroism and computer methods for molecular simulation docking.Secondly,the interaction mechanism of theaflavin(TF1),theaflavin-3-gallate(TF2)and theaflavin-3,3'-disgallate(TFDG)with bovine lactoferrin(b LF)were comparative studied.Finally,based on the conclusions of theaflavin-3,3'-disgallate(TFDG)on the structural conformation of bovine lactoferrin(b LF),the effects of bovine lactoferrin on its functionality were further explored.The main research contents and results of this article are as follows:1.The first part briefly described the classification structure and functional activity of theaflavin,the structure and function of proteins,and summarized the research methods for the interaction mechanism of theaflavin and transporters.In addition,the research progress of theaflavin and protein,as well as the significance of this topic,the research content and innovations were also elaborated.2.The interaction mechanism between TF1/TF2/TFDG and HSA/GHSA and its influence on the conformation of HSA/GHSA structure were studied by spectroscopic methods such as fluorescence spectroscopy,ultraviolet-visible spectroscopy,and circular dichroism.Multispectral results showed that TF1/TF2/TFDG quenched the endogenous fluorescence of HSA/GHSA by static quenching.Calculated from the fluorescence data,there was no significant difference between the quenching ability of TF1/TF2/TFDG for HSA and the quenching ability for GHSA.For HSA/GHSA,the quenching ability of three theaflavins on protein's intrinsic fluorescence intensity of the protein was TFDG>TF2>TF1.The interaction forces of TF1/TF2/TFDG with HSA/GHSA were mainly hydrophobic interaction forces.In addition,the results of ultraviolet-visible absorption spectrum,synchronous fluorescence spectrum,and three-dimensional fluorescence spectrum showed that the interaction of TF1/TF2/TFDG with HSA/GHSA formed complexes and affected the microenvironment of protein amino acid residues.According to the further exploration of circular dichroism,it was concluded that TF1/TF2/TFDG affected the secondary structure of HSA/GHSA: the addition of TF1/TF2/TFDG resulted in the reduction of the ?-helix of HSA,while ?-turn,anti-parallel,parallel and random curl increased to varying degrees.However,the addition of TF1/TF2/TFDG resulted in an increase in the ?-helix of GHSA,while ?-turn,anti-parallel,parallel and random curl showed varying degrees of decline.Finally,through site competition experiments,it was found that the binding site of TF1/TF2/TFDG on HSA/GHSA was site II,and this conclusion had been further verified in molecular docking.3.The interaction mechanism of TF1/TF2/TFDG with b LF and its effect on the conformation of b LF structure were comparative studied by spectroscopic methods such as fluorescence spectroscopy,ultraviolet-visible spectroscopy and circular dichroism.Multispectral results showed that TF1/TF2/TFDG quenched the endogenous fluorescence of b LF by static quenching.And the quenching ability to the intrinsic fluorescence intensity of b LF was:TFDG>TF2>TF1.According to the results of ultraviolet-visible absorption spectrum,synchronous fluorescence spectrum,and three-dimensional spectrum,it was found that TF1/TF2/TFDG complexed with b LF to form a complex,and the effect on the amino acid microenvironment of b LF was very weak,but it would cause changes in protein structure.According to the results of circular dichroism research,it was further found that the addition of TF1/TF2/TFDG would cause the ?-helix of b LF to increase,while ?-turn,anti-parallel,parallel and random curl would all decrease correspondingly.In addition,the results showed that the effect of the addition of TFDG on the changes of the secondary structural components of b LF was significantly stronger than that of TF1/TF2 on b LF.4.The effects of TFDG on the functional properties of b LF were studied using iron binding force experiment,enzyme-linked immunosorbent assay and in vitro digestion.According to the results of the iron binding force experiment,it was found that the addition of TFDG increased the ability of b LF to bind iron,which indicated that TFDG could enhance the iron transfer ability of b LF.The ELISA data showed that the addition of TFDG reduced the sensitivity of b LF.The results of in vitro digestion experiments revealed that the digestibility of TFDG-b LF complex in the gastric and intestinal stages was significantly lower than that of pure protein,indicating that the addition of TFDG was beneficial to increase the intestinal stability of bLF.