Oxygen diiron

The oxygen-carrying function is performed in some invertebrates by haemerythrin which, in spite of its name, does not contain haem. It is a diiron-oxygen protein. See K. K. Anderson and A. Gralund, Adv. Inorg. Chem. 43, 359-408 (1995). 

Diiron-Oxygen Proteins K. Kristoffer Andersson and Astrid Graslund... 

In the field of nonheme iron complexes, Miinck, Collins, and Kinoshita reported the oxidation of benzylic alcohols via stable p-oxo-bridged diiron(IV) TAME complexes, which are formed by the reaction of iron-28 complexes with molecular oxygen (Scheme 23) [142]. 

The successful deoxygenation of the sulfoxide 18a by either hexachlorodisilane as the reducing agent, or diiron nonacarbonyl according to the deoxygenation-complexation route can also be rationalized in terms of electrophilic attack of the reagents used on the nucleophilic sulfoxy oxygen. 

Fig. 2. Possible structures for a diiron(III) peroxide unit in the peroxo intermediate consistent with available Raman and Mossbauer spectroscopic data. The symbols N and 0 designate nitrogen and oxygen donor atoms of histidine and glutamate residues, respectively. Some of the latter must be bidentate to fill the coordination spheres.

Fig. 3. Proposed routes for conversion of the peroxo intermediate to intermediate Q, one involving loss of water (left-hand side) and one not (right-hand side). In the former case the resulting diiron(IV) oxo species could bind an oxygen atom with one iron, or the oxygen could be bound symmetrically by both iron atoms. Although written as an iron(IV) oxo species, Q can also be formulated as an iron(III) oxyl radical complex (35,51).

Magnetic coupling, between dimeric iron ions, diiron-oxygen proteins, 43 365-366 Magnetic interactions, 20 134-142 direct cation-cation, 20 139, 140 indirect cation-anion-cation, 20 140-142 Magnetic measurements, 32 58 Magnetic moments... 

Resonance Raman parameters, diiron-oxygen proteins, 43 367 Resonance Raman spectroscopy... 

Proteins with dinuclear iron centres comprise some well studied representatives like ribonucleotide reductase (RNR), purple acid phosphatase (PAP), methane monooxygenase hydroxylase (MMOH), ruberythrin and hemerythrin. The latter is an oxygen carrier in some sea worms it has been first characterized within this group and has thus laid the foundation to this class of iron coordination motif. Ruberythrin is found in anaerobic sulfate-reducing bacteria. Its name implies that, in addition to a hemerythrin-related diiron site another iron is coordinated in a mononuclear fashion relating to rubredoxin which is an iron-... 

Each polypeptide chain of the P2 dimer or R2 protein contains a diiron center which serves as a free radical generator 354a b/C A few bacteria utilize a dimanganese center.355 Oxygenation of this center is linked to the uptake of both a proton and an electron and to the removal of a hydrogen atom from the ring of tyrosine 166 to form HzO and an organic radical (Eq. 16-23) 356-360... 

The first example of iron-catalyzed asymmetric oxidation of sulfides was described by Fontecave and coworkers in 1997 [163]. An oxo-bridged diiron complex, which contained (—)-4,5-pinenebipyridine as chiral ligand, was reported to catalyze sulfide oxidations with H202 in acetonitrile, having the potential to transfer an oxygen atom directly to the substrates. However, the enantioselectivity of this process remained rather low (<40% ee, Scheme 3.53). 

Figure 9 Common oxygen activation mechanism proposed for nonheme diiron enzymes.

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