透過您的圖書館登入
IP:44.200.144.68
  • 學位論文

鎳鐵氫化酵素以及含鎳超氧化物歧化酶之含鎳生物模擬化合物之研究與探討

Biomimetic Nickel-Containing Model Compounds for [NiFe] Hydrogenase and Nickel Superoxide Dismutase (NiSOD)

指導教授 : 廖文峯
若您是本文的作者,可授權文章由華藝線上圖書館中協助推廣。

摘要


鎳鐵氫化酵素中含有鎳鐵異核之催化活性中心,可進行氫氣的活化,鎳鐵氫化酵素在進行氫氣的催化時會有許多氧化還原態,其中一個具有催化的活性型態Ni-C為[(Scys-H)(Scys)NiIII(μ-Scys)2(μ-H) Fe(CO)(CN)2],含有一個橋接的hydride配位基介於鎳鐵之間,在模擬化合物研究上,利用[NiIII(OR)P(C6H3-3-SiMe3-2-S)3]– (R = Ph or CH2Ph) 與 HBpin (pin = OCMe2CMe2O) 在THF中並且在–80℃下進行HBpin-promoted hydride-alkoxide metathesis reaction 可形成熱不穩定含有末端配位基為hydride的化合物 [PPN][NiIII(H)(P(o-C6H3-3-SiMe3-2-S)3)] (1),分別用低溫紫外/可見光光譜儀及低溫電子順磁順光譜儀鑑定之,化合物1與CS2 會進行插入反應形成[PPN][NiIII(1-S2CH)(P(o-C6H3-3-SiMe3-2-S)3)] (2). 將化合物1溶於 d-THF 與 CDCl3 反應可產生已知化合物 [NiIII(Cl)(P(o-C6H3-3- SiMe3-2-S)3)]– 以及CHDCl2,其在1H NMR (δ 5.46 (t) ppm (C4D8O))具有特徵吸收峰,此反應也間接證實[NiIIIH]-containing 化合物1的存在。 含有四芽基配位的[P(o-C6H3-3-SiMe3-2-S)3]3–-supported Ni(III)-imidazole [Ni(Im)(P(o-C6H3-3-SiMe3-2-S)3)] (Im = imidazole) (3) and Ni(III)-methylimidazole [NiIII(MeIm)(P(o-C6H3-3-SiMe3-2-S)3)] (6) (MeIm = methylimidazole) 可捕捉超氧化物進行氧化反應形成氧氣並分別產生[NiII(Im)(P(o-C6H3-3-SiMe3-2-S)3)]– (4) 與 [NiII(MeIm)(P(o-C6H3-3-SiMe3-2-S)3)] (7),化合物 4因為含有電子豐富的[NiII(P(o-C6H3-3-SiMe3-2-S)3)] motif 以及可提供質子的咪唑配位基,具有良好的電子環境可活化氧氣產生以咪唑配位基當作橋接的 [{Ni(P(o-C6H3-3-SiMe3-2-S)3)}2(m-Im-H)]– (Im-H = deprotonated imidazole) (5) 以及副產物H2O, 而Ni(III)-methylimidazole-containing complex 6 and Ni(II)-methylimidazole- containing complex 7 則在 O2- 與 O2 環境下可進行可逆的氧化還原反應,利用[NiII/III(Im)(P(o-C6H3-3-SiMe3-2-S)3)]0/1的一個電子氧化還原反應可將超氧化物轉換成氧氣最後形成水釋放,其中推測會經過一個[{Ni(P(o-C6H3-3-SiMe3-2-S)3)}2(Im)2(m2-O2)] 過渡態,此研究結果顯示此咪唑配位基可提供一個質子給鄰近的peroxide有利幫助形成H2O2。

並列摘要


[NiFe] hydrogenase containing [Ni-Fe] active center has been suggested to be the catalytic site for hydrogen activation. The catalytically active form Ni-C of [NiFe] hydrogenase was proposed to exist as the [(Scys-H)(Scys)NiIII(μ-Scys)2(μ-H) Fe(CO)(CN)2] with a hydride (H-) bridging between the Ni and Fe atoms. In model study, Reaction of complex [NiIII(OR)P(C6H3-3-SiMe3-2-S)3]– (R = Ph or CH2Ph) with HBpin (pin = OCMe2CMe2O) in THF at –80℃ undergoes HBpin-promoted hydride-alkoxide metathesis reaction to produce the thermally unstable [NiIII-H]-containing [PPN][NiIII(H)(P(o-C6H3-3-SiMe3-2-S)3)] (1) characterized by low-temperature UV-vis, EPR. Insertion of CS2 into the thermally unstable Ni(III)-hydride [PPN][Ni(H)(P(o-C6H3-3-SiMe3-2-S)3)] (1) generates [NiIII-1-S2CH]-containing [PPN][NiIII(1-S2CH)(P(o-C6H3-3- SiMe3-2-S)3)] (2). Reaction of the d-THF solution of complex 1 and CDCl3 yielding the very characteristic CHDCl2 identified by 1H NMR (δ 5.46 (t) ppm (C4D8O)) and the known [NiIII(Cl)(P(o-C6H3-3-SiMe3-2-S)3)]– also supports the existence of [NiIIIH]-containing complex 1 at –80 ℃. Both the tetradentate [P(o-C6H3-3-SiMe3-2-S)3]3–-supported Ni(III)-imidazole [Ni(Im)(P(o-C6H3-3-SiMe3-2-S)3)] (Im = imidazole) (3) and Ni(III)-methylimidazole [NiIII(MeIm)(P(o-C6H3-3-SiMe3-2-S)3)] (6) (MeIm = methylimidazole) catalyze oxidation of O2 to yield O2 along with [NiII(Im)(P(o-C6H3-3-SiMe3-2-S)3)]– (4) and [NiII(MeIm)(P(o-C6H3-3-SiMe3-2-S)3)] (7), respectively. Complex 4, composed of the electron-rich [NiII(P(o-C6H3-3-SiMe3-2-S)3)] motif and proton-provider imidazole-coordinate ligand, provide an optimum electronic condition to activate O2 producing imidazolate-bridged [{Ni(P(o-C6H3-3-SiMe3-2-S)3)}2(-Im-H)]– (Im-H = deprotonated imidazole) (5) and H2O, in contrast to the reversible interconversion between Ni(III)-methylimidazole-containing complex 6 and Ni(II)-methylimidazole- containing complex 7 under the presence of O2- and O2, respectively. That is, redox shuttling between the Ni(III) and Ni(II) states of [NiII/III(Im)(P(o-C6H3-3- SiMe3-2-S)3)]0/1 regulates superoxide-to-oxygen-to-H2O transformation, presumably, via the proposed transition state [{Ni(P(o-C6H3-3-SiMe3-2-S)3)}2(Im)2(2-O2)]. The results gained in this study may lend support to the suggestion that imidazole ligand could function as proton transfer to the nascent peroxide in the substrate reduction step of the NiSOD mechanism (Nired + O2- + 2H+ → Niox + H2O2).

參考文獻


25. Wuerges, J.; Lee, J. W.; Yim, Y. I.; Yim, H. S.; Kang, S. O.; Carugo, K. D. Proc. Natl. Acad. Sci. U.S.A. 2004, 101, 8569–8574.
47. Lee, C.-M.; Chen, C.-H.; Liao, F.-X.; Hu, C.-H.; Lee, G.-H. J. Am. Chem. Soc. 2010, 132, 9256–9258.
21. (a) Youn, H. D.; Kim, E. J.; Roe, J. H.; Hah, Y. C.; Kang, S. O. Biochem. J. 1996, 318, 889–896. (b) Youn, H. D.; Youn, H.; Lee, J. W.; Yim, Y. I.; Lee, J. K.; Hah, Y. C.; Kang, S. O. Arch. Biochem. Biophys. 1996, 334, 341–348.
1. Peck, H. D.; Pietro, A. San; Gest, H. Proc. Natl. Actad. Sci. U.S.A. 1956, 42, 13.
2. Casalot, L.; Rousset, M. TRENDS in Microbiol. 2001, 9, 228-237.

延伸閱讀