Modeling the diiron centers of non-heme iron enzymes. Preparation of sterically hindered diiron(II) tetracarboxylate complexes and their reactions with dioxygen

被引:76
作者
LeCloux, DD [1 ]
Barrios, AM [1 ]
Mizoguchi, TJ [1 ]
Lippard, SJ [1 ]
机构
[1] MIT, Dept Chem, Cambridge, MA 02139 USA
关键词
D O I
10.1021/ja981216s
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
A series of diiron(II) complexes, [Fe-2(mu-L)(mu-O2CR)(O2CR)(N)(2)], where L is a dinucleating bis(carboxylate) ligand based on m-xylylenediamine bis(Kemp's triacid imide) and N is a pyridine- or imidazole-derived ligand, were prepared; as models for the: carboxylate-bridged non-heme diiron cores of the O-2-activating enzymes, soluble methane monooxygenase-hydroxylase (MMOH), and the R2 subunit of ribonucleotide reductase (RNR-R2). X-ray crystallographic studies revealed differences in the coordination geometry of the bridging monocarboxylate ligand, which shifts from monodentate to syn,syn-bidentate bonding modes. The extent of this carboxylate shift depends on both the steric bulk of the monocarboxylate and the basicity of the ancillary N-donor ligands. Exposure of these diiron(II) complexes to O-2 at -77 degrees C in nonpolar solvents (CH2Cl2, THF, toluene) yielded deep blue solutions (lambda(max) approximate to 580 nm, epsilon approximate to 1200 M-1 cm(-1)), consistent with the generation of diiron(III) peroxo species. This reaction was irreversible, and its stoichiometry was determined by manometry to be 1:1 in diiron(Il) complex and O-2. The diiron(III) peroxo complexes exhibited oxygen isotope-sensitive resonance Raman bands at similar to 860 cm(-1), which are assigned to the O-O stretching frequency of a mu-1,2-peroxodiiron(III) core. Fe-57 Mossbauer spectroscopy confirmed the assignment of the diiron(III) oxidation level and indicated that the two iron sites have inequivalent environments (delta(1) approximate to 0.47 mm s(-1), Delta E-Q1 approximate to 0.88 mm s(-1); delta(2) approximate to 0.63 mm s(-1), Delta E-Q2 approximate to 1.20 mm s(-1)). Kinetics experiments provided rate constants for the reaction and revealed it to be first order in both diiron(II) complex and O-2. The factors controlling the rate of formation of the blue species and its stability are discussed.
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页码:9001 / 9014
页数:14
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共 46 条
[1]  
Battino R., 1981, OXYGEN OZONE, V7
[2]   Engineering the diiron site of Escherichia coli ribonucleotide reductase protein R2 to accumulate an intermediate similar to Hperoxo, the putative peroxodiiron(III) complex from the methane monooxygenase catalytic cycle [J].
Bollinger, JM ;
Krebs, C ;
Vicol, A ;
Chen, SX ;
Ley, BA ;
Edmondson, DE ;
Huynh, BH .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1998, 120 (05) :1094-1095
[3]  
BURDI D, 1997, STEENBOCK S P BIOSYN, V25, P85
[4]   SIR88 - A DIRECT-METHODS PROGRAM FOR THE AUTOMATIC SOLUTION OF CRYSTAL-STRUCTURES [J].
BURLA, MC ;
CAMALLI, M ;
CASCARANO, G ;
GIACOVAZZO, C ;
POLIDORI, G ;
SPAGNA, R ;
VITERBO, D .
JOURNAL OF APPLIED CRYSTALLOGRAPHY, 1989, 22 :389-393
[5]   NOVEL 1-PHENYLCYCLOALKANECARBOXYLIC ACID-DERIVATIVES AS POTENTIAL ANTICONVULSANT AGENTS [J].
CALDERON, SN ;
NEWMAN, AH ;
TORTELLA, FC .
JOURNAL OF MEDICINAL CHEMISTRY, 1991, 34 (11) :3159-3164
[6]   MOSSBAUER SPECTROSCOPIC STUDIES OF HEMERYTHRIN FROM PHASCOLOSOMA-LURCO (SYN. PHASCOLOSOMA-ARCUATUM) [J].
CLARK, PE ;
WEBB, J .
BIOCHEMISTRY, 1981, 20 (16) :4628-4632
[7]  
Dickson DominicP. E., 1986, MOSSBAUER SPECTROSCO
[8]   DIOXYGEN BINDING TO DIFERROUS CENTERS - MODELS FOR DIIRON OXO PROTEINS [J].
DONG, YH ;
MENAGE, S ;
BRENNAN, BA ;
ELGREN, TE ;
JANG, HG ;
PEARCE, LL ;
QUE, L .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1993, 115 (05) :1851-1859
[9]   Models for nonheme diiron enzymes.: Assembly of a high-valent Fe2(μ-O)2 diamond core from its peroxo precursor [J].
Dong, YH ;
Zang, Y ;
Shu, LJ ;
Wilkinson, EC ;
Que, L ;
Kauffmann, K ;
Münck, E .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1997, 119 (51) :12683-12684
[10]   Crystal structure analysis of a synthetic non-heme diiron-O-2 adduct: Insight into the mechanism of oxygen activation [J].
Dong, YH ;
Yan, SP ;
Young, VG ;
Que, L .
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 1996, 35 (06) :618-620