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Rare earth its complexes Microperoxidase , enzyme interaction mechanism

Author: ZhangLinQun
Tutor: LuTianHong
School: Nanjing Normal University
Course: Physical and chemical
Keywords: Microperoxidase-8 , -11 Cytochrome C Hemin Rare earth ions Eu3 Rare earth ternary complexes Coordination UV - visible absorption spectrum Electrochemical methods Electrospray ionization mass spectrometry
CLC: O641.4
Type: Master's thesis
Year: 2007
Downloads: 104
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Abstract


In recent years, can promote the improvement of crop yield and quality, the application of rare earth fertilizers in agriculture is more and more widely. A large number of studies have shown that the biological mechanism of rare earth ions in reasonable concentration can improve crop anti-virus, can promote the process of photosynthesis, light energy conversion, can also stimulate the growth of cells, to improve such as catalase (CAT biological activity), peroxidase (POD) and peroxide dismutase (SOD) enzyme, its chemical mechanism is not yet understood, research in this area is less. The main reason is that these enzymes have a high chemical activity, structural complexity, conformational flexibility, more difficult to study the interaction of these enzymes with rare earth ions. Therefore, the papers selected micro peroxidase a similar activity center and the biological activity of micro-peroxidase -11 (MP-11), micro-peroxidase -8 (MP-8) as a model compound to Eu 3 is representative of the rare earth ion by UV - visible (UV-vis) absorption spectroscopy, electrochemical methods and electrospray ionization mass spectrometry study of MP-11, MP-8 and chlorinated The heme and Eu 3 of interaction, and also to study the interaction of the rare earth ternary complexes with Eu 3 : for further study of the rare-earth ions and their complexes with the interaction of the enzyme to lay the foundation. The main results are as follows: 1. Eu 3 study of the mechanism of interaction with the MP-11 (1) When the MP-11 solution Eu 3 , due to the rare earth ions are easy to bond with oxygen, and two propionic acid groups on the heme porphyrin ring carboxyl oxygen exposure of the MP-11 molecule and a negative charge, Eu 3 Priority two carboxyl oxygen with the MP-11 molecule key cooperation with, form a complex. Increased two propionic acid groups from the porphyrin ring nearer EU 3 and the keys of the two carboxyl oxygen combined hemoglobin porphyrin ring of non-planar, π-π transitions * need less energy, reduce π-π * electronic transition probabilities. Due to the formation of hydrogen bonds in the peptide chain, the carbonyl groups on the peptide chain is embedded in the hydrophobic groups in the peptide chain, Therefore, EU 3 substantially no MP-11 peptide chain carbonyl oxygen cooperation with keys. (2) Electrospray Ionization Mass Spectrometry, MP-11 solution Eu 3 , the formation of complexes Eu 3 with the MP-11, the molar ratio of 1 Eu 3 solution with the MP-11 molar ratio increased, only the reaction more completely and no new complexes generated on a member of Eu 3 with only part of MP-11 bonded. Electrochemical experiments also confirmed this conclusion, i.e., when Eu 3 and MP-11 molar ratio of less than 1:00, Eu 3 are substantially the MP-11 in containing group occurs bonded complexes oxidation reduction peak in the cyclic voltammetry curves only observed without Eu 3 of redox peaks. When the concentration of Eu 3 is greater than 1, in addition to the complex redox peaks, but also observed Eu 3 a pair of redox peaks, indicating when Eu 3 of MP-11 molar ratio greater than 1, the excess the Eu 3 ion is no longer with the MP-11 ligand. Therefore, in the Eu 3 form complexes with the MP-11, in a molar ratio of 1. (3) When the MP-11 with Eu 3 formation of the complexes, the complexes redox peak-to-peak potential difference △ Ep ratio of the smaller of the MP-11, the peak current ratio of MP-11 large, The electrochemical reaction described complexes reversible than the MP-11. This is due to the Eu 3 and MP-11 the interaction, Eu 3 with the MP-11 molecule heme porphyrin ring two carboxyl oxygen key cooperation with, the non-planarity of the porphyrin ring of the heme increased, resulting heme porphyrin ring of Fe in the degree of exposure to the increase caused. In addition, the electrochemical activity of the complexes on the oxygen reduction is higher than the MP-11, indicating that Eu 3 after ligand and MP-11, can increase the biological activity of the MP-11. 2. Micro-peroxidase peptide chain structure of its interaction with hemin (Hemin has) Eu 3 , MP-8, MP-11 and cytochrome C (Cyt c) and Eu 3 interaction to study micro peroxidase peptide chain length on its interaction with rare earth ions, and lay the foundation for further study of the mechanism of the interaction of enzymes with rare earth ions. (1) UW-vis absorption spectra of studies have shown that interaction with Eu 3 , Hemin has, MP-8, MP-11 and Cyt c Soret band absorption peak intensity are decreased, the peak position have taken place in the redshift. The decline in Hemin has Soret band absorbance peak redshift are the largest, and the smallest change of Cyt c. Hemin the porphyrin ring is not connected to the peptide chain, its negative charge of the two carboxyl groups of the acid group of the completely bare of oxygen, most easily with the Eu 3 bonded. Most Cyt c heme molecules porphyrin ring connected to a peptide chain, but also the most complex, propionic acid group on the porphyrin ring is almost completely embedded, the lowest degree of nudity of the carboxyl oxygen, the most difficult and Eu 3 bonding. MP-8, and MP-11, due to the different length of the peptide chain caused by the different ways they are gathered. MP-11 in end-to-end the random manner aggregation, each MP-11 molecule heme plane is not parallel, the structure is relatively loose, Eu 3 and its role, the cause of the heme of non-planar increase the extent. MP-8 molecules are heme plane parallel to the close-packed manner aggregation, so the MP-8 heme of the original non-planarity to be lower than the MP-11, Eu 3 acting hemoglobin prime non-planarity of the increase is also more difficult and MP-8, and MP-11, the original of the Soret band peak position 396 and 399nm were also proved MP-8 original planarity higher than the MP-11. Therefore, the degree of red shift of the Soret band peak in descending order in Hemin> MP-11 MP-8> Cyt-c, the Soret band peak intensity decline, in a sequence as in Hemin MP-8> MP- 11> Cyt c. (2) Electrochemical findings, Eu 3 and of Hemin, MP-8, and MP-11 can be bonded to a molar ratio of 1 complexes. However, while EU 3 with Hemin the bond strongest in their complexes of the cyclic voltammetry curves substantially observed less redox peaks, indicating that Eu 3 hinder Hemin the electrochemical reaction. MP-8 and MP-11, Eu 3 to promote the electrochemical reaction. Since the stacking mode of the MP-11 MP-8 compared loose, therefore, Eu 3 and the role of the MP-11 induced heme non-planarity of the degree of increase is greater than the MP-8, so Eu 3 role in promoting the electrochemical reaction of MP-11 to be greater than the MP-8. Is formed due to the hemoglobin in the Cyt c are buried in the length of the peptide chain, Eu 3 not substantially its heme bonded complexes. Therefore, Eu 3 the Cyt c electrochemical reaction without impact. 3. The the lanthanum-VB 6 - Ternary Complex with MP-11 interaction in this chapter select POD MP-11, a model compound for the study by the UV-vis absorption spectroscopy, circular dichroism (CD) spectrum and electrochemical methods, systems lanthanum - glycine (Gly) - Vitamin B6 (VB 6 ) ternary complexes (LaLCl 2 ) with the interaction of the MP-11 . (1) by LaLCl 2 ternary complexes UV and MP-11 UV-vis absorption spectra of discovery, when both the molar ratio of less than 5, the peak position of the Soret band almost did not change while the peak Strong increase, but when the molar ratio is gradually increased to greater than 10, the position of the peak of the Soret band is red shift and the absorption intensity decreased. This may indicate that the MP-11 LaLCl 2 interaction in two ways, namely low molar ratio of the MP-11 to promote the role of high molar ratio of inhibition. And the ternary complexes with the MP-11 after bonding has occurred, leading to increased non-planarity of the heme of the porphyrin ring, the decrease in the energy required by the π-π * transition and π-π * reduces the chance of the electronic transition. (2) through LaLCl , 2 ternary complexes found with the CD spectra of the MP-11, 2 added in LaLCl , affect the secondary structure of the MP-11 peptide chain Soret band, so that a slight red shift, molar ellipticity decreased. Complex concentration increases with the ordered structure increased, decreased, suggesting that a sustained increase in the concentration of the complexes they undermine ordered secondary structure, and further lead to increased non-planarity of the MP-11 heme. (3) through LaLCl 2 electrochemical experiments of the ternary complexes with the MP-11 found, LaLCl 2 and MP-11 complexes electrochemical reactions prevail reversible the and diffusion-controlled. And at a molar ratio of 3:00, LaLCl 2 role in promoting the electrochemical reaction of MP-11 is the most significant, but when the molar ratio is further increased, the promoting effect but with increasing molar ratio gradually reduce. It also reflects the LaLCl 2 and MP-11 interaction 2 ways. Short, the ternary complexes with the MP-11 directly to key in cooperation with MP-11 secondary structure of the peptide chain, thereby affecting change the microenvironment of the heme around, so that the non-planar increase of heme, promoting MP -11 electrochemical reaction.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Structural Chemistry > Complex chemistry ( coordination chemistry )
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