Study On The Effect Of Shape Of CdS Nanoparticles On Their Interact Ion With EcoRI

CdS NPs (Cadmium sulfide nanoparticles) has special physical and chemicalproperties, such as small size and high specific surface area. These properties producehigh surface energy which allows a strong adsorption and binding ofbiomacromolecule to CdS NPs. Protein is an important biological macromolecule, andas nanotechnology is drawing more and more attention, interaction betweennanoparticles and biological molecules becomes a research hotspot of bionanotechnology. In this work we choose EcoRI (restriction endonuclease, colibacillus extract)as protein model of interaction, it is a very important protein in biological body andtends to resist invading DNA while protecting its own DNA, thus consisting immuneand defense system. Due to the close relationship between disease and expression ofprotein in most cases, we could determine the physiological functions of protein ordetect important substances in biological body by the studies on the conformationchanges and physical-chemical parameters changes of protein which contributes a lotto the research into biological medicine, clinical medicine and so on. Our work ismainly as follows:The first section: we obtained CdS nanocubes through one-pot synthesis, andthen made it linked with hydrophilic carboxyl groups through MUA surfacemodification. FTIR datas showed that the secondary structure content of EcoRI,which is also called conformation, underwent changes. The following UV absorptionspectrum, fluorescence spectrum and gel electrophoresis technology all proved thesuccessful interaction between them, inspite of that, we analysed the quenchingmechanism of CdS nanocubes to EcoRI and the interaction force between them.According to quenching constants and binding constant, we find pH7.2to be theoptimal pH environment for EcoRI-CdS nanocubes. Agarose electrophoresisdetermined the conservation of enzyme activity after the interaction.The second section: by means of some common spectrum and gel electrophoresistechnology, we took researches into the interaction between EcoRI and CdS nanorods.pH7.2was also found to be environment in which EcoRI and CdS nanorodsinteracts severely, thus getting a good repeatability. Besides, we analysed thequenching of CdS nanorods to EcoRI is static quenching dominant, and results aboveprovided us with theory basis for a better understanding of the binding process. The last lane in agarose electrophoresis figure became light, which indicated that theEcoRI-CdS nanorods interaction affected enzyme activity of EcoRI, yet not totallyinactived.The third section: we used the same solvothermal method as that in the secondsection to synthesis CdS multipods. We utilized fluorescence spectrum to performexperiment on variable temperature, and classified the queching mechnism of CdSmultipods to EcoRI to static quenching. The interaction force can be determined bythe related thermodynamic parameters calculated. As shown in FTIR spectra, afterconjugated with CdS multipods, secondary structure content of EcoRI showed anincrease of α-helix structure and a decrease of β-sheets and turns. Finally, weseparately conjugated EcoRI with CdS NPs of three different shapes, and thenconducted contrast test using agarose electrophoresis enzyme activity test, by the testwe found that CdS NPs of all the three shaps can’t make EcoRI totally inactived,that’s to say, the enzyme was conserved to some degree.