Functional Analogues of Cytochrome c Oxidase, Myoglobin, and Hemoglobin

Collman, James P.; Boulatov, Roman; Sunderland, Christopher J.; Fu, Lei

doi:10.1002/chin.200420283

Cited by 61 publications

(124 citation statements)

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“…Second, it clearly identifies the importance of the superoxo as the "resting state" for catalysis, a fact long known for the O 2 reduction chemistry of Pacman porphyrins. 39 Finally, the mechanistic cycle clarifies some perplexing observations that porphyrin templates bearing a distal metal-binding cap exhibit comparable selectivities for the four-proton, fourelectron pathway with or without a second redox-active metal ion bound in the distal cap. 17,30,31 The mechanism shown in Figure 7 suggests that the second functional site, whether that be another porphyrin, a metal complex, or a metal-free coordination sphere, is to adjust the pK a of the protonated dioxygen adduct.…”

Section: A Pcet Mechanism For O 2 Reduction By Pacman Constructsmentioning

confidence: 78%

Role of Proton‐Coupled Electron Transfer in O—O Bond Activation

Rosenthal

Nocera

2007

ChemInform

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The selective reduction of oxygen to water requires four electrons and four protons. The design of catalysts that promote oxygen reduction therefore requires the management of both electron and proton inventories. Pacman and Hangman porphyrins provide a cleft for oxygen binding, a redox shuttle for oxygen reduction, and functionality for tuning the acid-base properties of bound oxygen and its intermediates. With proper control of the proton-coupled electron transfer events, O-O bond breaking of oxygen, and more generally oxygenated substrates, may be achieved with high efficiencies. The rule set developed for oxygen reduction may be applied to a variety of other small molecule activation reactions of consequence to energy conversion.

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Section: A Pcet Mechanism For O 2 Reduction By Pacman Constructsmentioning

confidence: 78%

Role of Proton‐Coupled Electron Transfer in O—O Bond Activation

Rosenthal

Nocera

2007

ChemInform

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“…The level of oxidative stress may increase in the presence of destabilizing hemoglobin mutations or chain imbalance leading to thalassemia. Three systems in which oxidative stress has recently been highlighted are sickle cell disease, thalassemia, and hemoglobin C disease [2][3][4][5][6][7]. Sickle cell disease is caused by a substitution of valine for glutamic acid at the β-6 position in the hemoglobin β-chain.…”

Section: Introductionmentioning

confidence: 99%

Heme degradation and oxidative stress in murine models for hemoglobinopathies: Thalassemia, sickle cell disease and hemoglobin C disease

Nagababu

Fabry

Nagel

et al. 2008

Blood Cells, Molecules, and Diseases

102

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Red blood cells with abnormal hemoglobins (Hb) are frequently associated with increased hemoglobin autoxidation, accumulation of iron in membranes, increased membrane damage and a shorter red cell life span. The mechanisms for many of these changes have not been elucidated. We have shown in our previous studies that hydrogen peroxide formed in association with hemoglobin autoxidation reacts with hemoglobin and initiates a cascade of reactions that results in heme degradation with the formation of two fluorescent emission bands and the release of iron. Heme degradation was assessed by measuring the fluorescent band at ex 321 nm. A 5.6 fold increase in fluorescence was found in red cells from sickle transgenic mice that expressed exclusively human globins when compared to red cells from control mice. When sickle transgenic mice co-express the γM transgene, that expresses HbF and inhibits polymerization, heme degradation is decreased. Mice expressing exclusively hemoglobin C had a 6.9 fold increase in fluorescence compared to control. Heme degradation was also increased 3.5 fold in β-thalassemic mice generated by deletion of murine β major . Membrane bound IgG and red cell metHb were highly correlated with the intensity of the fluorescent heme degradation band. These results suggest that degradation of the heme moiety in intact hemoglobin and/or degradation of free heme by peroxides are higher in pathological RBCs. Concomitant release of iron appears to be responsible for the membrane damage that leads to IgG binding and the removal of red cells from circulation.

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“…Nature notably employs metalloporphyrins with Fe or Co centers as prosthetic groups to handle respiratory gases, sensing and catalytic functions, whereby a plethora of model systems has been investigated to disentangle the underlying elementary chemical binding mechanisms. 1,2,3 In recent years it became clear that the conformational flexibility of the porphyrin macrocycle sensitively interferes as a decisive factor in the regulation of the pertaining functional properties, 4,5,6,7,8,9,10 however, many questions remain regarding the intricate interplay between structural distortions and the ligation of small adducts. Here we report a molecular-level investigation on the interaction of carbon monoxide with simple Fe and Co tetraphenyl-porphyrin model systems adopting a distinct saddle-shape conformation, one of the prominent nonplanar macrocycle geometries, following adsorption on a smooth metal surface.…”

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confidence: 99%

Cis-dicarbonyl binding at cobalt and iron porphyrins with saddle-shape conformation

et al. 2011

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Diatomic molecules attached to complexed Fe or Co centers are significant for many biological processes. In natural systems notably metallotetrapyrrole units carry respiratory gases or provide sensing and catalytic functions. Conceiving synthetic model systems strongly helped to rationalize the pertaining chemical foundations, whereby recent work highlights the importance of the prosthetic groups' conformational flexibility as an intricate variable affecting their functional properties.Here we present simple model systems to investigate at the single-molecule level the interaction of carbon monoxide with saddle-shaped Fe-and Co-porphyrin conformers, which have been stabilized as two-dimensional arrays on well-defined surfaces. Using scanning tunneling microscopy we identified a novel bonding scheme expressed in tilted monocarbonyl and cis-dicarbonyl configurations at the functional metalmacrocycle unit. Density functional theory modeling reveals that the weakly bonded diatomic carbonyl adduct can effectively bridge specific pyrrole groups with the metal atom because of the pronounced saddle-shape conformation of the porphyrin cage.

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Functional Analogues of Cytochrome c Oxidase, Myoglobin, and Hemoglobin

Abstract: For Abstract see ChemInform Abstract in Full Text.

Cited by 61 publications

References 1 publication

Role of Proton‐Coupled Electron Transfer in O—O Bond Activation

Role of Proton‐Coupled Electron Transfer in O—O Bond Activation

Heme degradation and oxidative stress in murine models for hemoglobinopathies: Thalassemia, sickle cell disease and hemoglobin C disease

Cis-dicarbonyl binding at cobalt and iron porphyrins with saddle-shape conformation

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