Inhibitory Effect Of EGCG On A?40 Aggregation At Membrane Surface

Alzheimer's disease(AD)is closely related to the aggregation of amyloid-? protein(A?).The A? aggregation process is very complex and involves the effects of cell membranes in addition to the interaction between A? molecules and molecules.However,the development of small molecule inhibitors has neglected the effect of cell membrane on the inhibition of A? aggregation and severely hindered the development of high-performance A? inhibitors.Therefore,it is very important to study the mechanism of small molecules on the cell membrane to inhibit the aggregation of A?.In this paper,gallocatechin gallate(EGCG)was selected as a small molecule inhibitor.Three small monolayer vesicles were synthesized and characterized.The mechanism of EGCG on the aggregation of A?40 was studied by means of biophysics,biochemistry and cell biology.The results of ThT fluorescence showed that the inhibitory effect of EGCG on A?40 was concentration-dependent on the surface of liposomes,which was consistent with the results in free solution.The results of atomic force microscopy showed that EGCG could completely inhibit the formation of A?40 fibers in the presence of low concentration inhibitor EGCG,compared with free solution and the amount of short fibers produced in the presence of liposomes.The results of CD show that EGCG concentration has a significant effect on A?40 conformational transformation.In the cytotoxicity test,the inhibitor EGCG was also chemically dependent on the cell viability.After adding the low concentration inhibitor EGCG,the cell viability was lower under liposomes compared to free solution.In addition,a silicon ball wrapped with erythrocyte membrane(silicon membrane)with a true physiological cell diameter(about 5 ?m)was selected.The results of ThT fluorescence show that the surface of the silicon membrane can accelerate the process of A?40 aggregation and shorten the delay period of the protein,but it does not increase the number of finally produced fibers.The results showed that the inhibitory effect of EGCG on protein A?40 was also concentration-dependent in in situ and non-in situ ThT experiments.The initial fluorescence value of the protein was higher in the silicon and the silicon membrane system.After adding the low concentration inhibitor EGCG,the protein fluorescence value was higher under the silicon membrane,and the inhibition effect of the inhibitor EGCG was poor.In the AFM experiment,as the concentration of the inhibitor EGCG increased,the number of finally produced fibers decreased gradually.After adding the low concentration inhibitor EGCG,the number of short fibers produced in the silicon membrane system is more.The CD showed that the high concentration inhibitor EGCG could inhibit the conformational transformation of A?40 on the surface of the silicon membrane,and its final conformation was mainly ?-helix and irregular curl.The results of cytotoxicity test showed that the inhibitor EGCG could significantly enhance the survival rate of the cells on the surface of the silicon membrane and was in a concentration-dependent manner.In summary,EGCG on the surface of liposomes and silicon membrane can also inhibit the aggregation of A?40 in a concentration-dependent manner.This study can provide some theoretical support for the development of in vivo inhibitors.