Evaluation Of Molybdenum Disulfide And Pesticides Effects On Amyloid Fibrillation Using Atomic Force Microscopy

Amyloidosis is caused by a variety of risk factors, and it is important to discover and interfere the controllable risk factors for lowering the incidence of these diseases. One of the most prominent hallmarks of amyloidosis is the insoluble fibrils deposited in the extracellular spaces of organs and tissues. Based on our knowledge, although the relationship between amyloidosis and chemical reagents which are known as one of the environmental factors have been reported currently, it is still not systematic and comprehensive enough in the academic research on the relationship between nanomaterials and amyloidosis or between pesticides and amyloidosis. Most researches have been focused on epidemiological and experimental studies which can get information about the etiology of these diseases and disease prevention methods at the macroscopical level. Considering that the study on the intermolecular interactions at the molecular level can get more chemical and biological information which provides a theoretical basis for the analysis of the interactions between moleculars, it is indispensable to investigate the effect of nanomaterials and pesticides on the kinetics of amyloid fibrillation.In this thesis, hen egg white lysozyme was used as a model protein. A comprehensive study in regard to the relationship between environmental factors and protein amyloid fibrillation was investigated by atomic force microscope (AFM) imaging measurement. The main contents were as follows:1. Evaluation of molybdenum disulfide (MoS2) nanosheets effects on the amyloid fibrillation using AFM imaging measurement.The lysozyme was incubated with different kinds of MoS2 nanosheets and the effects of MoS2 nanosheets on amyloid fibrillation were investigated using AFM. And other technologies, such as thioflavin T fluorescence spectroscopy, circular dichroism and intrinsic fluorescence spectroscopy were also used to explain the mechanism. The results showed that MoS2 nanosheets promoted the rate of lysozyme fibrillation with the increase of the concentrations of MoS2 nanosheets, and single-layer MoS2 nanosheets exhibited a stronger acceleration on lysozyme fibril formation than the few-layer MoS2 nanosheets.It was speculated that a mechanism might be due to the combination interactions of hydrophobic interactions, electrostatic interactions and van der Waals forces between MoS2 nanosheets and lysozyme which might induce a locally higher concentration of lysozyme monomers on the nanosheet surface. What's more, the protein conformational changes might lead to an enhancement of self-organization into ordered or pre-ordered layer as a template for further fibrillation.2. Evaluation of pesticides effects on the amyloid fibrillation using AFM imaging measurement.The lysozyme was incubated with different kinds of pesticides. Then the effects of pesticides on amyloid fibrillation were investigated using AFM. The results showed that dicofol, thiophanate-methyl and cyfluthrin showed the acceleration of amyloid fibrillation, while triadimefon, dimethoate, chlorothalonil and carbaryl had no effects on amyloid fibrillation. In addition, the above seven kinds of pesticides had no effects on the morphology of amyloid fibrils. According to the results of surface plasmon resonance and tryptophan intrinsic fluorescence spectroscopy, it was speculated that the three kinds of accelerating pesticides interacted with lysozyme respectively and then induced the changes of protein conformational changes, which would promote the formation of amyloid fibrils.