Conformational Effects Of Myoglobin By Different Functional Carbon Nanotubes

Nanomaterials are a new class of materials that exhibit peculiar physical and chemical properties such as light,electricity,heat and mechanics.This has enabled nanotechnology used in various research fields,attracting many scientists at home and abroad.Nanotechnology has also become the hottest research hotspot.Carbon nanotubes are one of the most promising nanomaterials.The wide application of carbon nanotubes makes them widely presented in the environment,and their environmental and health risks have also received extensive attention.Protein,a complex organic macromolecule,is a basic substance that constitutes cells,and a major bearer of life activities.Every reaction in an organism requires the participation of proteins.Carbon nanotubes can enter the organism directly or indirectly through the blood-staining barrier,and this behavior causes the interaction of proteins with carbon nanotubes.The biological function of the protein thus may be affected the carbon nanotubes.Therefore,it is necessary to understand the interaction between carbon nanotubes and proteins in living organisms.In this thesis,the mechanism of interaction between six carbon nanotubes(original single-walled carbon nanotubes,carboxylated single-walled carbon nanotubes,hydroxylated single-walled carbon nanotubes,original multi-walled carbon nanotubes,carboxylated multi-walled carbon nanotubes and hydroxylated multi-walled carbon nanotubes)and myoglobin were studied by UV-vis absorption spectroscopy,fluorescence spectroscopy,simultaneous fluorescence spectroscopy and circular dichroism.The experimental results showed that these six carbon nanotubes enhanced the UV absorption of myoglobin and cause the blue shift of the peak position,which indicated that these six carbon nanotubes had strong interaction with myoglobin.In the fluorescence emission spectrum,the fluorescence intensity of myoglobin decreased,which indicated that the fluorescence quenching of six carbon nanotubes and myoglobin occurred.The fluorescence quenching mechanism of these six carbon nanotubes to myoglobin belongs to the type of quenching combined with dynamic and static.The binding constants,binding sites and thermodynamic parameters of these six carbon nanotubes interacting with myoglobin at different temperatures were calculated.The type of interaction between these six carbon nanotubes and myoglobin was studied and the reaction was a spontaneous process.Synchronous fluorescence spectroscopy and circular dichroism analysis showed that the original,hydroxylated and carboxylated single-walled carbon nanotubes decreased the ?-helix content of myoglobin from 57.04% to 42.87%,51.41% and 46.92%,respectively.While,the original,hydroxylated and carboxylated multi-walled carbon nanotubes increased the ?-helix content of myoglobin from 15.02% to 23.82%,22.97% and 28.02%,respectively.These indicates that the six carbon nanotubes change the secondary structure of myoglobin,causing the main peptide chain of myoglobin to be unfolded or rearranged.