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Investigation of Mimic Phosphate Hydrolytic Enzymes Using Rare Earth Complexes and Rare Earth Micelle

Author: ZhouTong
Tutor: XieAnJian
School: Anhui University
Course: Physical and chemical
Keywords: metal complex metallomicelle BNPP hydrolysis gemini surfactant
CLC: O621.13
Type: Master's thesis
Year: 2010
Downloads: 35
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Abstract


Simulation of metal enzymes is the research focus of the chemistry and biomimetic chemistry in recent years. Especially, metal complexes and metallomicelles are widely employed as artificial hydrolase. In this dissertation, the hydrolysis of bis (p-nitrophenyl) phosphate (BNPP) catalyzed by different complexes formed from a series of rare earth metals and several simple ligands have been investigated. And the effects of four kinds of micelles on the catalytic hydrolysis reaction were studied. The main contents are summarized as follow:1. Bis(p-nitrophenyl) phosphate (BNPP) was synthesized as DNA model. The hydrolysis of BNPP catalyzed by a series of rare earth metal ions (including Ce(Ⅲ)、La(Ⅲ)、Eu(Ⅲ)、Y(Ⅲ)、Sm(Ⅲ)) in the presence of two amino alcoholic ligands has been discussed. The kinetic results indicate that all the five kinds of rare earth complexes are very effective catalysts for BNPP hydrolysis. The hydrolysis rate of BNPP was improved by 3.03×108 times and 1.14×109 times to Spontaneous hydrolysis catalyzed by the most effective Ce(Ⅲ) complexes.The effects of pH value, temperature and Ce(Ⅲ)concentration on the hydrolysis of BNPP catalyzed by Ce(Ⅲ)-Triethanolamine(TEA) and Ce(Ⅲ)-diethanolamine (DEA) complexes were studied. The results show that the catalytic properties of two complexes are similar. The apparent rate constants of the hydrolysis reaction increase rapidly with the increasing Ce(Ⅲ) concentration in the low concentration, and then slow down until "saturation". The changes of the apparent rate constant kobsd with the pH value are both bell-shaped curves. And the constants also increase with the increasing temperature, the apparent activation energies of the two reactions were figured out by Arrhenius formula. The catalytic active species and mechanism of hydrolysis reaction was discussed at last.2. The hydrolysis of BNPP catalyzed by five different complexes formed by a series of rare earth metal ions Ce(Ⅲ), La(Ⅲ), Eu(Ⅲ), Y(Ⅲ), Sm(Ⅲ)and barbital sodium(BS) has been discussed. The hydrolysis rate of BNPP was improved by 1.52×108 times (kobsd=1.67×10-3s-1) to Spontaneous hydrolysis catalyzed by the most effective Ce(Ⅲ)-BS complexes. The mole ratio of Ce(Ⅲ) to BS in catalytic activity species obtained from the Job curve of the hydrolysis of BNPP catalyzed by the Ce(Ⅲ)-BS system is 1:2. The changes of the apparent rate constant kobsd with the pH value are bell-shaped curves. And the constants also increase with the increasing temperature, the apparent activation energy of the hydrolysis reaction was figured out by Arrhenius formula. At last the catalytic mechanism of hydrolysis reaction was discussed.3. The effects of the two novel cation gemini surfactants [C16H33N+(CH3)2-(CH2)2-N+(CH3)2C14H29].2Br- (C16-2-C16), [C,4H29N+(CH3)2-CH2-O-CO2-CH2-N+(CH3)2C14H29].2Br- (C14-1-C14) on the hydrolysis of BNPP catalyzed by the Ce(Ⅲ)-TEA and Ce(Ⅲ)-BS system were studied, and were compared with the two traditional surfactants cetyltrimethylammonium bromide(CTAB) and triton X-100. The results show that, the apparent rate constants of BNPP hydrolysis kobsd catalyzed by the two rare earth complexes in CTAB micelle were about an order of magnitude lower. The kobsd were increased by 1.87 times and 2.44 times to Spontaneous hydrolysis are very effective catalysts for BNPP hydrolysis.The hydrolysis rate of BNPP was improved by 3.03×108 times and 1.14×109 time to Spontaneous hydrolysis in triton X-100 micelle, and in C16-2-C16 micelle they were increased by 5.16 times and 1.85 times to Spontaneous hydrolysis. Hydrolysis of BNPP catalyzed by two kinds of rare earth complexes showed different results in C14-1-C14 micelle. We suppose that this is closely related to special structure of C14-1-C14.

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