Prion Protein Induced Aggregation Of CdTe QDs And Their Application In Biological Analysis

Quantum dots, also known as semiconductor nanocrystals, are a novel type of fluorescent nanomaterials developed in recent years. They attracted a growing notice in biological research due to small diameter (similar with nucleic acids and proteins), perfect optical property (broad absorption, narrow emission, strong light stability, etc.), biocompatibility, etc., and they have been widely applied to cell and in vivo imaging, the study of fluorescence resonance energy transfer, and detection of biological macromolecules. Prion protein is a kind of infectious protein which could cause many neurodegenerative diseases in animal and human. The pathogenic mechanism is the misfolding of normal PrPc which form theβ-sheep-rich and protease-resistant PrPSc. The unstable PrPSc possesses a high tendency to aggregate and form oligomers, the precursor of amyloid fiber and amyloid plaques. The main work on this thesis can be summarized as follows:(1) CdTe QDs with excellent fluorescent properity were synthesized and modified by mercaptoacetic acid, and high purity of prion protein was purified from Escherichia coli. Subsequently, we discussed the aggregation of CdTe QDs induced by prion protein and the effects of CdTe QDs on the progress of fibrosis of prion protein.(2) Based on the aggregation of CdTe QDs induced by prion protein, CdTe QDs were used as a fluorescent probe for colorimetric qualitative and semi-quantitative detection of prion protein. Meanwhile, both the decrease in fluorescence intensity and the blue-shift of maximal emission peak of the supernatant could be used for quantitative detection of prion protein. Interference test showed that this detection had high selectivity and sensitivity. To demonstrate the potential application of this detection system, we also detected prion protein in the diluted solution of Escherichia coli lysate. Finally, transmission electron microscopy results showed that fibrils existed in the precipitates and were partly transformed to amyloid plaques.(3) According to the phenomenon that prion protein precipitated with larger CdTe QDs preferentially and caused the blue-shift of maximal emission peak of the supernatant, we used prion protein as a "biological separating reagents" to separate three different sizes of CdTe QDs, including the separation of two kinds of CdTe QDs, and three kinds of CdTe QDs from each other. In addition, the recoveries of these separation methods were calculated and the mechanism was discussed.