| Nowadays, more attention has been paid to the protection and optimization of the environment, the influence of environment pollutants on living beings as well as the control and treatment of pollutants. Many investigations indicated that the actions of the different metal elements in living beings are different. However, the mechanisms are not understood very well. Many investigations have demonstrated that the anti-oxidases, such as superoxidase dismutases (SOD), catalases (CAT), peroxidases (POD) are very sensitive to the effects of metal ions. Because of the complexity of enzymes, model compounds, whose structures and functions are similar to the active sites of enzymes, have been used to investigate the interaction of the enzymes with metal ions and then to study the mechanisms of the interaction of anti-oxidases with heavy metal ions. This method has been widely accepted by researchers in different countries. Therefore, in this thesis, microperoxidase-11 (MP-11) was selected as a model of POD to study the mechanisms and regularities of its interaction with some metal ions using electrochemical method, UV-vis absorption spectroscopy and circular dichroism spectroscopy. It will lay the foundation for the study of the interactions of metal ions with biomacromolecules. The main results obtained are as follows.1. The electrochemical and spectroscopic behaviors of MP-11 in the in the aqueous solution and simulated physiological solution, i.e. the solution of 20% methanol and phosphate buffer solution with 20% methanol are compared. It was found that in the simulated physiological solution, the hydrogen bindings between some amido groups in the MP-11 molecules are decomposed and the MP-11 dimers become monomers. It induces the increase in the contents of the a-helical and (3-turn conformation, the decrease in the content of the random coil conformation of MP-11 as well as the increase in the exposure extent of the heme group. Therefore, the reversibility of the electrochemical reaction and the electrocatalytic activity of MP-11 for H2O2 reduction increase comparing the situation in the aqueous solution.2. Because the nutrient metal ions, such as Na+, Ni2+, Co2+, Mn2+ and Zn2+ caninteract with MP-11 through the electrostatic effect, not the binding action, they affect the secondary structure and the electrochemical behavior of MP-11 to some extent.3. The contents of the a-helical and P-turn conformation in the secondary structure of the MP-11 molecule increase and the content of the random coil conformation decreases due to the coordination of Cd2+ with S in the peptide of MP-11 firstly. In addition, after the binding of MP-11 with Cd2+, MP-11 with the positive charges would diffuse toward to the glassy carbon electrode with the negative charge easily. Thus, Cd2+ can promote the electrochemical reaction of MP-11. However, because Cd2+ does not directly interact with the heme group, it affects the structure of the heme group little bit. For example, the position of the Soret band does not change. Only its intensity changes to a certain extent.4. The interaction between La3+ and MP-11 would decrease in the intensity of the Soret band and shift the band position, because of the strong coordination action of La3+with O of the carboxyl group in the heme group and weak interaction of La3+ with O of the amido group in the peptide. The interaction also increases in the non-planarity of the heme group. In the same time, it would increase in the contents of the a-helical and p-turn conformation in the secondary structure of the MP-11 molecule and decrease in the content of the random coil conformation, leading the increase in the exposure extent of heme group. Therefore, the reversibility of the electrochemical reaction increases. In addition, after the binding of MP-11 with La3+, MP-11 with the positive charges would diffuse toward to the glassy carbon electrode with the negative charge easily. Thus, it further promotes the electrochemical reaction of MP-11.5. When the biomolecules interact with... |
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