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颗粒甲烷单加氧酶(pMMO)是甲烷氧化菌中催化甲烷氧化生成甲醇的一种酶.Methylococcus capsulatus IMV 3021的pMMO活性位点是pmoB亚基,该亚基是一种可溶性蛋白.我们研究将pmoB亚基进行异源表达及生物催化活性的验证.当培养基中烟酰胺腺嘌呤二核苷酸(NADH)浓度为5 mmol/L时,可以观察到异源表达pmoB亚基具有催化甲烷氧化成甲醇活性,生成甲醇浓度为1.04 mmol/L.研究pMMO活性对于开发能直接将甲烷转化成甲醇的新型、环保催化剂有非常重要意义. 相似文献
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苯乙烯生物催化氧化制环氧苯乙烷的研究 总被引:2,自引:0,他引:2
1.引言 单加氧酶是氧化还原酶的一类,因其能够活化分子氧并将其中一个氧原子插入到有机化合物中而引起广泛的研究兴趣。甲烷单加氧酶广泛存在于多种烷烃氧化菌、烯烃氧化菌和酵母等微生物中。已经发现、甲烷单加氧酶在细胞中负责将甲烷转变成甲醇(图1)。 此外,甲烷单加氧酶能催化氧化相当多的化合物,其中许多反应都是化学上不易实现的。例如,C_1—C_8烷烃的羟化,C_2—C_4烯烃的环氧化等等。该酶作为催化剂突出的优点还在于它在催化氧化时表现出的高立体选择性,其酶促过程往往可以获得有光学活性的产品。从 相似文献
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随着天然气以及页岩气为代表的非常规天然气的大规模开采,甲烷作为化工原料的直接转化利用受到了越来越多的关注.然而,甲烷分子具有极其稳定的正四面体结构,其物理化学性质非常稳定,如具有高达439 kJ/mol的C-H键能、极弱的电子亲和力、相当大的离子化能量和低的极化率,这都使得甲烷分子C-H键的活化相当困难.如何实现甲烷直接高效催化转化被誉为催化领域的'皇冠式'课题.与经甲烷重整制合成气,然后通过F-T合成获取化学品的间接转化法相比,甲烷直接转化无论在物料、能量转换效率还是在设备成本、环境保护等方面都有着非常明显的优势.以甲烷氧化偶联以及非氧化偶联(如无氧芳构化等)为典型代表的甲烷直接转化研究不断取得突破,但其各自都存在一定的局限性.相比于热催化转化路径,电催化转化路径在许多方面存在着十分明显的优势:(1)反应条件温和,甚至在常温常压条件下也能实现甲烷电催化转化反应的发生;(2)可调控程度高,仅需调节关键实验参数如电压和电流等,就能实现对反应过程热力学以及动力学的调控;(3)能够利用可再生电能驱动甲烷转化反应的发生,可将低品阶的电能转化并存储为化学能.本文采用Ni中空纤维作为基底,在其表面构筑NiO活性层,将NiO@Ni中空纤维作为电极,实现了常温常压条件下的甲烷电催化转化.通过X射线衍射、扫描电镜、透射电镜等表征手段,确定了中空纤维特有的多孔三维结构、气体传输规律、NiO活性层分布状态等物化性质.通过电化学交流阻抗与循环伏安等测试手段,获得了电荷传递、电化学活性比表面积等电化学性质.恒电压电氧化甲烷研究发现,1%NiO@Ni中空纤维具有最优的催化活性,分别在1.44 V与1.46 V(vs.RHE)电势下获得54%的甲醇法拉第效率和85%的乙醇法拉第效率. 相似文献
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从甲基弯菌M ethylosinus trichosporium IMV3011的膜中分离出颗粒性甲烷单加氧酶(Particulate MMO,Pmmo)t和NADH脱氢酶,只有当两者同时存在,并添加去垢剂解离膜组分时,NDAH才能为pMMO提供还原当量,对苯二酚能够在整细胞和膜水平代替NADH作为PMMO的电子供体,对于纯化的PMMO,对苯二分配仍是有效的电子供体,而NADH却是无效的电子供体。在NADH脱氢酶存在下,NADH可将对苯醌还原为对苯二酚,纯化过程中,采用对苯二酚作为PMMO活性分析时的电子供体,不必共纯化NADH脱氢酶,且有利于对PMMO活性中心进行深入研究。 相似文献
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采用甲醇蒸气作为碳源对甲基弯菌IMV 3011进行驯化培养,然后逐渐增加液态甲醇的浓度使其适应,得到了能耐受甲醇(φ(MeOH)=1%)的甲基弯菌IMV 3011.对甲基弯菌IMV 3011进行甲烷-甲醇共培养可得到大量具有甲烷单加氧酶(MMO)活性的细胞.研究了添加甲醇对甲基弯菌IMV 3011生长和MMO活性的影响,发现甲醇能够促进甲基弯菌IMV3011的生长.在批式反应器中,添加甲醇能够提高甲基弯菌IMV 3011的催化环氧化能力,说明甲醇可以作为电子供体通过再生辅酶NADH驱动环氧丙烷合成.考察了在膜反应器中用细胞悬浮液连续合成环氧丙烷的可行性.结果表明,通过192 h连续抽提产物环氧丙烷,避免了其对环氧化反应的抑制,流出液中环氧丙烷的浓度仍保持在1.35 mmol/L左右. 相似文献
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已有研究证明了Cu-MAZ分子筛催化甲烷部分氧化的优异性且实验表征得出其活性结构含有三核铜结构. 为进一步提高部分氧化活性, 采用MAZ分子筛作为载体体系, 用于三核[Cu3(μ-O)3]2 , 活性结构分别掺杂Pd、Pt、Fe、Co、Ni、Au和Ag, 构建[Cu2MO3]2 异金属活性位. 通过密度泛函理论(DFT)研究不同金属对Cu-MAZ催化甲烷部分氧化反应的能量变化和反应活性的影响, 并分析了活性位、反应中间体、过渡态等结构的几何和电子结构性质, 根据以上结果进一步得到描述符. 相似文献
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Sunney I. Chan Steve S.-F. Yu Chih-Cheng Liu Chung-Yuan Mou 《Current Opinion in Green and Sustainable Chemistry》2020
Methanotrophs mediate the conversion of methane (CH4) into methanol selectively and efficiently near ambient conditions so we can learn from microbes to develop biomimetic catalysts capable of performing this difficult chemistry. This review highlights the development of a tricopper cluster catalyst that functions similar to the particulate methane monooxygenase enzyme in methanotrophic bacteria. The performance of this catalytic system formulated for quasi-heterogeneous catalysis is compared with other heterogeneous catalysts derived from Cu- and Fe-based zeolites and Cu mordenites known to activate CH4 stoichiometrically near 200 °C. We also highlight a unique catalytic system, in which the oxidizing power of both O atoms of the O2 molecule can be harnessed for oxidation of toluene to yield benzaldehyde at room temperature. 相似文献
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Peter Haack Christian Limberg 《Angewandte Chemie (International ed. in English)》2014,53(17):4282-4293
Research on O2 activation at ligated CuI is fueled by its biological relevance and the quest for efficient oxidation catalysts. A rarely observed reaction is the formation of a CuII‐O‐CuII species, which is more special than it appears at first sight: a single oxo ligand between two CuII centers experiences considerable electron density, and this makes the corresponding complexes reactive and difficult to access. Hence, only a small number of these compounds have been synthesized and characterized unequivocally to date, and as biological relevance was not apparent, they remained unappreciated. However, recently they moved into the spotlight, when CuII‐O‐CuII cores were proposed as the active species in the challenging oxidation of methane to methanol at the surface of a Cu‐grafted zeolite and in the active center of the copper enzyme particulate methane monooxygenase. This Minireview provides an overview of these systems with a special focus on their reactivity and spectroscopic features. 相似文献
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The diiron active sites of the reduced hydroxylases from methane monooxygenase (MMOH(red)) and toluene/o-xylene monooxygenase (ToMOH(red)) have been investigated by X-ray absorption spectroscopy (XAS). Results of Fe K-edge and extended X-ray absorption fine structure analysis reveal subtle differences between the hydroxylases that may be correlated to access of the active site. XAS data were also recorded for each hydroxylase in the presence of its respective coupling protein. MMOB affects the outer-shell scattering contributions in the diiron site of MMOH(red), whereas ToMOD exerts its main effect on the first-shell ligation of ToMOH(red); it also causes a slight decrease in the Fe-Fe separation. These results provide an initial step toward delineating the differences in structure and reactivity in bacterial multicomponent monooxygenase proteins. 相似文献
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Karasevich E. I. Karasevich Yu. K. Shestakov A. F. Shilov A. E. 《Kinetics and Catalysis》2003,44(2):247-259
According to the mechanism of alkane hydroxylation, whose main postulate is the formation of an intermediate complex containing pentacoordinated carbon, the hydroxylation of methane and ethane by methane monooxygenase was kinetically simulated by the numerical method. The published data on the kinetic isotope effects of oxidation of deuterium-substituted methane molecules (CHD3, CH2D2, and CH3D) and the distribution of products of chiral ethane (R- and S-MeCHDT) oxidation by methane monooxygenase were examined. The kinetic models proposed for the oxidation of isotopically substituted methane and ethane are in good agreement with experimental data. 相似文献
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The role of iron and copper in particulate methane monooxygenase (pMMO) of Methylosinus trichosporium OB3b is described, and an overview of the enzyme's properties is presented. The pMMO from M. trichosporium OB3b was solubilized in the detergent n-dodecyl--D-maltoside and purified by chromatographic techniques. The enzyme consists of 0.9 iron atoms and 12.8 copper atoms per molecule. The iron site in pMMO may be mononuclear non-heme iron. Copper exists as either copper ion coupled to four nitrogen atoms and/or trinuclear copper cluster wherein copper ions are ferromagnetically coupled. 相似文献
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《Journal of molecular catalysis. A, Chemical》1999,137(1-3):161-168
The effect of metal ions on particulate methane monooxygenase (pMMO) was studied. The pMMO activity in the membranes was partially inhibited by ethylenediaminetetraacetic acid (EDTA), but remained more than 70% of the as-isolated membranes. The activity of the EDTA-treated membranes was strongly influenced by the addition of metal ions. Among the metal ions, copper ion stimulated the activity, indicating that copper was needed for the activity. When duroquinol and dioxygen were introduced to the EDTA-treated membranes, the electron spin resonance signal of copper did not change, suggesting that the copper cluster did not play as an electron transport and may have another function, such as active site of pMMO or regulator of the activity. On the other hand, the iron signal (g=5.98) decreased by the addition of duroquinol, dioxygen and acetylene, showing an iron atom is contained in the active site of pMMO. 相似文献
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Karasevich E. I. Karasevich Yu. K. Shestakov A. F. Shilov A. E. 《Kinetics and Catalysis》2003,44(1):112-120
Published data on the kinetic isotope effects of the hydroxylation of deuterium-substituted methane molecules (CHD3, CH2D2, and CH3D) by methane monooxygenase are examined in the framework of the two-step nonradical mechanism through the intermediate formation of a complex containing pentacoordinate carbon. The kinetic schemes with the first step involving one, two, and three hydrogen atoms of the oxidized substrate are considered. Contrary to the widely accepted oxygen rebound mechanism, the experimental results obtained for the oxidation of various substrates by methane monooxygenase and cytochrome P450 can be explained from the viewpoint of the dynamics of a general nonradical mechanism. 相似文献
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Martinho M Choi DW Dispirito AA Antholine WE Semrau JD Münck E 《Journal of the American Chemical Society》2007,129(51):15783-15785
Two methane monooxygenase (MMO) systems have been identified in methanotrophic bacteria, namely, a soluble or cytoplasmic MMO and a membrane-associated or particulate MMO. The active site of the well-characterized soluble MMO contains a bis-mu-hydroxo-bridged diiron cluster. X-ray crystallographic studies of the particulate enzyme, pMMO, have identified two copper centers on the alpha subunit (pmoB) of the alphabetagamma trimer and a site at the interface of the betagamma subunits filled by a Zn, apparently from the crystallization buffer. In our hands, pMMO preparations containing 1-2 iron atoms per alphabetagamma show the highest catalytic activity. We have employed M?ssbauer spectroscopy to characterize the iron in our preparations. Interestingly, we find in pMMO a component with the same spectral properties as the antiferromagnetically coupled diiron(III) cluster in the soluble enzyme. In whole cells, we find nearly 1 diiron center per alphabetagamma of pMMO; in purified enzyme preparations, only 10% of the sites appear to be occupied. These occupancies correlate well with the measured specific activities of purified pMMO and pMMO in whole cells. We suggest that it is the "Zn site" that accommodates the diiron center in active pMMO. 相似文献
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The kinetics of methane oxidation by methane monooxygenase is simulated numerically. Literature data on the distribution of products of the oxidation of deuterated methane CH4 ? n D n (CH3D, CH2D2, and CHD3), as well as on the kinetic isotope effect in the competitive oxidation of CH4 and CD4 by methane monooxygenase, are analyzed in the framework of a nonradical multistep mechanism. Kinetic schemes whose first step involves two hydrogen atoms of the oxidation substrate are considered. The kinetic models suggested for methane oxidation are in good agreement with experimental data. 相似文献