Structure and Mossbauer spectrum of a (mu-1,2-peroxo)bis(mu-carboxylato)diiron(III) model for the peroxo intermediate in the methane monooxygenase hydroxylase reaction cycle
Structure and Mossbauer spectrum of a (mu-1,2-peroxo)bis(mu-carboxylato)diiron(III) model for the peroxo intermediate in the methane monooxygenase hydroxylase reaction cycle
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DOI：
10.1021/ja9604370
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发表时间：
1996-05-22
影响因子：
15
通讯作者：
Lippard, SJ
中科院分区：
文献类型：
--
作者：
Kim, K;Lippard, SJ
细菌将甲烷作为其唯一的碳和能源来源的能力吸引了对CH活化感兴趣的化学家。1，2可溶甲烷单加氧酶(MMO)体系的关键催化组分是一个251 kDa的羟基酶，它含有两个非相互作用的羧酸桥联的双核非血红素铁中心。3-5最近，冷冻-猝灭动力学研究了从甲氧基球菌(BATH)中分离的MMO的还原羟基酶(HRED)组分与氧气的反应，得到了光学、拉曼和穆斯堡尔光谱，并初步归属于反铁磁性偶联(μ-PEROXO)二铁(III)中间体HPOXO。6，7在6 0 0-6 5 0 nm的吸收光谱和90 5 cm-1的νO-O伸缩频率支持这一归属，但穆斯堡尔谱(δ，0.6 6 mm S-1)的异构体位移不在先前报道的双铁(III)过氧络合物的范围内。虽然光谱鉴定了不稳定的过氧桥联二铁(III)络合物，但在本工作开始时还没有发表X射线结构测定，8、9，也没有一个具有Hperoxo的特定穆斯堡尔参数。因此，我们试图对可能的过氧基中间体的小分子类似物进行结晶学表征，并获得其穆斯堡尔谱，以便与过氧基的穆斯堡尔谱进行比较。一个可能的候选者是[Fe{HB(PZ‘)3}(O2CR)]，PZ’)3，5-二(异丙基)-吡唑基和R)Ph在低温下与氧气反应生成的蓝绿色物种。10通过对不同R基团(R)Ph(1a)、CH2Ph(2a)、p-tol(3a)、4-联苯(4a)和2-萘基(5a)的大量实验和结晶条件的研究，并借助基于ccd探测器的X射线衍射仪，我们最终成功地通过晶体化学分析(CCA)表征了一个这样的配合物：[Fe2(μ-1，2-O2)(μ-O2CCH2Ph)2-{HB(PZ‘)3}2]，2b。
The ability of bacteria to use methane as their sole source of carbon and energy has fascinated chemists interested in CH activation. 1, 2 The key catalytic component in soluble methane monooxygenase (MMO) systems is a 251 kDa hydroxylase enzyme containing two noninteracting carboxylate-bridged dinuclear non-heme iron centers. 3-5 Recently, freeze-quench kinetic studies of the reaction with dioxygen of the reduced hydroxylase (Hred) component of MMO from Methylococcus capsulatus (Bath) afforded optical, Raman, and Mössbauer spectra which were tentatively assigned to an antiferromagnetically coupled (μ-peroxo) diiron (III) intermediate designated Hperoxo. 6, 7 The optical absorption spectral band at 600-650 nm and the νO-O stretching frequency of 905 cm-1 supported this assignment, but the isomer shift in the Mössbauer spectrum (δ, 0.66 mm s-1) was outside the range of those previously reported for diiron (III) peroxo complexes. Although unstable peroxo-bridged diiron (III) complexes had been spectroscopically identified, no X-ray structural determination had been published at the inception of this work, 8, 9 and none had the specific Mössbauer parameters of Hperoxo. We therefore sought to characterize crystallographically a small molecule analog of the putative peroxo intermediate and to obtain its Mössbauer spectrum for comparison to that of Hperoxo. One likely candidate was the blue-green species formed in the reaction of [Fe {HB (pz′) 3}(O2CR)], pz′) 3, 5-bis (isopropyl)-pyrazolyl and R) Ph, with dioxygen at low temperature. 10 After extensive trials with different R groups (R) Ph (1a), CH2Ph (2a), p-tol (3a), 4-biphenyl (4a), and 2-naphthyl (5a)) and crystallization conditions, and with the power of a CCD-detector-based X-ray diffractometer, we finally succeeded in characterizing one such complex,[Fe2 (μ-1, 2-O2)(μ-O2CCH2Ph) 2-{HB (pz′) 3} 2], 2b, by crystallographic chemical analysis (CCA).