Study On The Effect Of Tannic Acid On Lysozyme Fibrillation

Protein fibrillation is a unique protein aggregation behavior.In vivo,protein fibrillation is generally believed to be closely related to a variety of devastating human diseases,including Alzheimer's disease,mad cow disease,Parkinson's disease,Huntington's disease,and type II diabetes.Although scientists have done a lot of research on this type of diseases,there is still a lack of effective treatment and effective drugs for these diseases.In view of the close relevance between protein fibrillation and these diseases,it is of great importance to explore organic inhibitors for protein fibrillation and to study related inhibition mechanism.This is undoubtedly of great significance for the treatment,prevention and drug design of protein fibrillation diseases.The effect of tannic acid on lysozyme fibrillation was studied in this paper.We used ThT fluorescence spectroscopy,Fourier transform infrared spectroscopy(FTIR)and atomic force microscopy(AFM)to systematically study the effects of tannic acid on the kinetics of lysozyme fibrillation,fibril morphology,and secondary structure of protein fibril.The mechanism of the intermolecular interaction between tannic acid and lysozyme was also studied by fluorescence quenching and synchronous fluorescence.We also discussed the discrepancy of experimental results obtained by fluorescence quenching at different temperatures,and pointed out a serious defect in previous experimental design in previous related studies.Details of our results are as follows:The results showed that low-concentration tannic acid could inhibit lysozyme fibrillation,and higher-concentration of tannic acid could induce the formation of non-fibril aggregates.Fluorescence study indicated that the quenching mechanism of tannic acid to lysozyme is static quenching.In the molecular complex,the proportion of the tannic acid and lysozyme is approximately 1:1,and there exists non-radiation energy transfer.When tannic acid interacting with lysozyme,tyrosine residues basically do not interact with on lysozyme,but the polarity of the microenvironment and the hydrophobicity of tryptophan residues will increase.In fibrillation temperature,323~333 range of K,lysozyme and tannic acid bind each other through hydrophobic interaction.Hydrophobic interaction between tannic acid and lysozyme will weaken the intermolecular forces to suppress lysozyme's self-assembly and destruct the assembly rich in beta-sheet structures,that inhibits fibrillation.The results of fluorescence quenching experiment on the interaction of tannic acid and lysozyme were found to be highly dependent on temperature.In the range of 298~308K,the binding of lysozyme to tannic acid is mainly hydrogen bonding and Van der waals force.This result is totally different from that obtained at high temperature.This study provides new methods and ideas for the in-depth understanding of the effects of organic molecules on protein fibrillation.New evidence has been provided for a comprehensive understanding of the effects of related organic molecules on protein fibrillation.