| With the rapid development of nanotechnology,research and application of nanomaterials in industry,daily necessities,medical treatment,monitoring and other fields become more and more wide,which makes a large number of nanomaterials enter and remain in environment.Because of their high reactivity,nanomaterials that entering environment can interact with environmental media,thus affecting their migration,deposition and transformation in environment.Meanwhile,interaction with nanomaterials will also cause some changes in environmental active substances,then changing the living environment of organisms or affecting elements cycle process.Not only that,nanoparticles existed in environment will enter the organism through respiration,direct contact,diet and other ways,then they will interact directly or indirectly with proteins,nucleic acids and other biomacromolecules,further affecting physiological functions or special properties of biomacromolecule.Due to the important physiological functions of proteins in organisms and in natural environment,it is of great significance to study the interaction between different nanomaterials and proteins in order to understand the biological and ecological toxicity of nanomaterials.This paper is divided into two parts:In the first part,interaction mechanism of human serum albumin(HSA)with carbon quantum dots(CQDs)and effect of interaction on protein structure and function were studied by using a variety of spectroscopy methods under the condition of simulating human physiological p H and osmotic pressure.Steady-state fluorescence spectra showed CQDs quenched the intrinsic fluorescence of protein by combining with HSA to form a 1:1 non-fluorescent compound,in the process hydrogen bond and van der Waals force were the main interaction forces.Results from site competition experiment and synchronous fluorescence spectra displayed the binding site of CQDs on HSA was close to the only tryptophan residue,which located in the subdomain ⅡA of HSA;Resonance light scattering,three-dimensional fluorescence,circular dichroism,UV-Vis absorption spectra and hydrophobic fluorescence probe detection experiment indicated binding with CQDs will increase α-helical conformational content in the secondary structure of HSA,causing structure further curling and folding,making protein’s aggregation degree falling.Moreover,the micro-environmental polarity around amino acid residues in HSA’s tertiary structure also reduced after interaction.Furthermore,it was found structural changes of HSA could affect its fibrillation and physiological functions,causing reduction of fibrillation degree and esterase-like activity,heightening free radical scavenging capability.In the second part,interaction of nano ceria with soil urease was also studied through various spectral detection methods.Firstly,it was found nano ceria would affect urease activity in soil,so the interaction and mechanism between nano ceria and urease were studied in detail from a molecular level.The research findings showed nano ceria quenched the intrinsic fluorescence of urease by a combination of static and dynamic quenching mechanism,and static quenching was the main quenching mechanism when the concentration of nanoparticles was low,while dynamic quenching enhanced gradually with the increase of nano ceria’s concentration.The main interaction force for their binding was electrostatic force,and hydrogen bond was also involved in.When urease molecules are bound to the surface of nanoparticles,it will promote the binding of other urease molecules.Interaction with nano ceria could change the secondary structure of urease,loosening its polypeptide skeleton structure,and increasing the polarity of microenvironment around amino acid residues in urease’s tertiary structure.Changes in urease structure made it more likely to aggregate,which promotes the formation of fibrosis.Therefore,it is speculated that urease activity change may be due to structural change of protein caused by interaction between urease and nano ceria. |
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