Study On The Interaction Between Protein And Bioactive Components And The Protection For Bioactive Components

People pay more attention to bioactive components due to their beneficial health effects.However,they are susceptible to oxidative degradation during processing and storage when exposed to environmental conditions(e.g.,light,oxygen,temperature).And many hydrophobic and amphiphilic bioactive components have poor solubility in an aqueous environment.The unfavorable factors lead to the loss of functionality of bioactive components and limit their application in industry.In addition,it appears to be a trend in functional foods that contain a range of bioactive components.Consequently,it is necessary to design edible carriers which can simultaneously bind multiple bioactive components and improve their stability.Protein can bind a lot of low-molecular-weight molecules to form protein-ligand complexes due to ligandbinding property.The formation of these complexes can improve both stability and solubility of ligands in aqueous solutions.However,most studies have focused on the interaction between proteins and a single ligand.Nowadays,more and more proteins with multiple ligand-binding sites are being reported.Therefore,study on the preparation of protein-multiligand complexes and the protection of bioactive components may provide more theoretical models and data support for further studies on the interaction mechanism between ligands and proteins.This study will also provide guidance for the development of carriers based on proteins for simultaneous encapsulation of multiple bioactive components.In this study,bovine serum albumin(BSA)was used as a model protein to study the interactions with hydrophobic retinol,amphiphilic resveratrol and hydrophilic(-)-epigallocatechin-3-gallate(EGCG).In addition,BSA and whey protein isolation(WPI)were used as carrier proteins to be investigated the protective effects on the storage stability of these ligands.The main contents are as follows:Firstly,in order to study whether BSA can simultaneously bind with retinol,resveratrol and EGCG,experiments were carried out to characterize binding of a ligand to BSA in the absence and presence of other ligands.Results suggest that BSA-triligand complexes could successfully formed when the ligands were added in the sequence of retinol,resveratrol,EGCG.The complex formation did not significantly affect the secondary structure of BSA but altered the protein tertiary structure.Secondly,the surrounding microenvironment of bioactive components was analyzed by using their own fluorescence.Results indicate that retinol,resveratrol,EGCG upon binding to BSA transferred into more hydrophobic environments to different extents.Furthermore,the site marker competitive experiments and molecular docking were carried out to identify the binding sites of these three ligands on BSA.Data gathered from the former experiment indicate that their binding on BSA did not locate within subdomain IIIA.Although partial ligands were bound within subdomain IIA,it was also not the main site for the binding of the three components.The results from molecular docking suggest that retinol,resveratrol and EGCG were bound within domain ? of BSA.Thirdly,the protective effects of BSA and WPI on the retinol,resveratrol and EGCG were also discussed during storage.When the concentration of BSA was 30 ?M,the contents of retinol and resveratrol were about 22% and 51%,respectively,in the BSA-triligand complexes after storage for 628 h.The content of EGCG was about 1% after storage for 100 h.These results suggest that the stability of these bioactive components was improved in the BSAtriligand complexes relative to free ones.WPI provided a protection for retinol and resveratrol,but could not delay the loss of EGCG.