Synthesis Of CdTe Quantum Dot Probes And The Application In Imaging Arabidopsis Roots

The discovery of new herbicide targets and their inhibitor lead structures is one of the key problems which restrict the development of high efficiency herbicides.It is important to establish a quick and easy method that can be utilized to define the localizationof a target,which is import to promote the development of new herbicides.In this paper,an a-alkyl indole acetic acid is used as the active molecule,and connected with different surface-modified CdTe quantum dots,and co-cultured with the model plant Arabidopsis Thaliana.By this way,we are able to localize the distribution of the bioactive fluorescent probes in Arabidopsis roots,with the expectation for the establishment of a method that can be used in the herbicide target discovery.The work in this thesis has three parts:1.In the part,the relevant background knowledges of this thesis,including the action mode of auxin,the target proteins,and the synthesis and application of quantum dots,are reviewed,and the research project of this thesis is planed.2.In the second part,the CdTe quantum dots(QDs)with three differently modified surfaces were synthesized.The three surface modifiers are:2-mercaptoacetic aicd(MAA),the mixtuaqueore of MAA and PEG with a terminal thiol group(HS-PEG-COOH),and a triple-function polymer(HS-LSA)synthesized in our lab.These QDs were characterized with surface morphology,spectroscopic characteristic,and the size by UV absorption spectroscopy(UV-vis),fluorescence emission spectra,transmission electron microscopy(TEM),dynamic light scattering(DLS),infrared spectroscopy(FTIR),and X-ray powder diffraction(XRD).The results showed that CdTe QDs prepared in us solution have good optical stability with uniform particle size of about 2-5 nm in diameter.Relatively,the QDs modified with the mixture modifier MAA/PEG exhibit a higher performance in these parameters.3.In the third part,fluorescent nanoprobes were synthesized through the covalent connections between CdTe QDs of different surface-modifiers and the biologically activeα-alkylindoleacetic acid.The solution stabilities in water,PBS buffer,and MS plant culture media were tested.The cytotoxicity of these fluorescent probes to the Arabidopsis plant also were examined.The results showed that CdTe-MAA/PEG with the concentration of the 0.25 mg/L were stable dispersions and low toxicity that were suitable for plant co-culture.Fluorescence inverted microscopy and confocal microscope were used to image the distribution and location of the fluorescent probes in Arabidopsis roots.It was found that the probes were mainly localized in the meristem epidermal cells and maturation zone cortical cells.The literature report that auxin receptor protein TIR1 mainly exists in the nucleus and the cell membrane,and auxin transporter protein PIN2 is mainly expressed in the apical epidermal and cortical cells.Therefore,the probes are likely binding specifically with the proteins TIR1 and PIN2,or both.