Transport, dioxygen

Erbium, tris(2,2,6,6-tetrametbyl-3,5-hep tanedione) structure, 1, 65, 66 Erbium complexes acetylacetone, 2, 374 Erhium(ill) complexes glycolic acid, 2, 472 Eriochalcite, 6, 855 Eriochrome black T metallochromic indicators, 1, 555 Eriochrome blue black R metallochromic indicators, I, 556 Eriochrome cyanine R metallochromic indicator, 1, 556 Erythrocruorin, 6, 689 dioxygen transport, 6,683 stability... 

Metal complexes of the porphyrins have been studied for many years. Such attention is not surprising, since particular derivatives play a central role in photosynthesis, dioxygen transport and storage as well as other fundamental processes such as electron transfer (Smith, 1975 Dolphin, 1978-9). Indeed, there are few compounds found in nature which can compare with the diversity of biochemical functions exhibited by the porphyrins. 

Table 1.5 Metals in Biological Systems Dioxygen Transport...

Iron, Fe2+ (d6) 6, octahedral A-Imidazole, porphyrin Dioxygen transport in hemoglobin and myoglobin... 

Oxygen transport (binuclear) Hemocyanin Mollusks and arthropods Dioxygen transport... 

The Functional Model. Synthesis of a chemically similar or dissimilar molecule that will mimic the desired function of the enzyme be it dioxygen transport, electron transport, isomerization, or small molecule reduction. 

The most striking feature of the peak or plateau current variation with substrate concentration is that the initial, and expected, increase is followed be a strong decrease that eventually annihilates catalysis. This decrease results from inhibition by the substrate, H202, which converts the E2 complex in the complex E3. E3 is the iron(II) dioxygen complex classically considered in dioxygen transport. It may regenerate E spontaneously by expulsion of the superoxide ion. This process is, however, very slow and the most important regeneration pathway involves the cosubstrate as pictured in Scheme 5.3. 

Despite the above aspects of the interaction of molecular oxygen with metal fragments, we will limit our electrochemical discussion to the reactivity of transition metal complexes with molecular oxygen in the context of modelling the dioxygen transport. 

The second class of dioxygen carriers is that of haemocyanins. These proteins, which contain a binuclear Cu(I) site (thus in the oxidized Cu(II) met form they belong to the so-called Type 3 copper proteins , which contain an EPR-silent dicopper active site), regulate dioxygen transport in the respiration of arthropods and molluscs. Figures 7 and 8 show... 

Copper, Cu ((f ) 5, square pyramid 6, tetragonal O-Carboxylate, A-imidazoIe Type II copper oxidases, hydoxylases Type III copper hydroxylases, dioxygen transport in hemocyanin... 

The first three-dimensional structure of a protein determined was the dioxygen transporter myoglobin isolated from sperm whale in the ferric form (86, 87). A 153 amino acid globular protein, myoglobin contains eight helical regions (A to H) with a single heme b bound between helices... 

Porphyrins and metalloporphyrins have been the subject of numerous investigations over the past century. This attention is not surprising if one considers that particular derivatives play central roles in essential biological processes such as photosynthesis, dioxygen transport and storage, and electron transfer. 

Copper 100 3 X 11T1 2 Many enzymes dioxygen transport... 

In the heme proteins the prosthetic group consists of iron coordinated to a substituted porphyrin. The versatility of the heme proteins is apparent in the range of different functions they perform, mediate or catalyze. These functions are associated with, for example, dioxygen transport (hemog-... 

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