Rare Earth Ions And Microperoxidase -11 Mechanism Of The Interaction

The application of rare-earth fertilizers in the agriculture was firstly suggested with Chinese scientists. A lot of investigations about the biological mechanism showed that the rare-earth fertilizers in the certain concentration range could increase the biological activities of some enzymes, such as peroxidase (POD). However, its chemical mechanism is still not clear and the investigation in this area is very few. Because of the high chemical activity, the structural complexity and the conformational flexibility of enzymes, it is difficult to study of the interaction of rare earth ions with enzymes. Therefore, in this thesis, as the model of POD, MP-11, whose active center and bioactivity are similar to POD, was selected and Yb³⁺ and La³⁺ were used as the typical rare earth ions to investigate the interaction of MP-11 with Yb³⁺ and La³⁺ using the electrochemical method and the UV-vis absorption spectroscopy. It would lay a foundation of the further investigation of the interaction of rare earth ions and their complexes with enzymes. The main results obtained are as follows:1. The interaction mechanism of Yb³⁺ with MP-11(1) The UV-vis absorption spectroscopic results indicated that after Yb³⁺ interact with MP-11, the peak position of the Soret band of MP-11 shifts to the red direction and the absorbance decreases. It means that because of the large exposed extent and the negative charge of the carbonyl oxygen of the metacetonic acid group in the heme group of the MP-11 molecule, Yb³⁺ coordinates firstly and strongly with the carbonyl oxygen of the metacetonic acid group in the heme group. It leads to the increase in the non-planarity of the porphyrin group in the heme group, the decrease in the energy and the probability for the π-π^* transition. Yb³⁺ interacts weakly with the carbonyl oxygen of the amido group in the peptide chain of the MP-11 molecule because the exposed extent of the carbonyl oxygen in the peptide chain is small due to the formation of the hydrogen bonds in the peptide chain. Furthermore, the carbonyl oxygen in the peptide...