The role of phosphorus in rhyolitic liquids as determined from the homogeneous iron redox equilibrium

1993 ◽  
Vol 113 (3) ◽  
pp. 424-435 ◽  
Author(s):  
Rosa Gwinn ◽  
Paul C. Hess
Keyword(s):  
Redox Equilibrium ◽  
Iron Redox

scholarly journals Iron Redox Chemistry and Implications in the Parkinson’s Disease Brain

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Dinendra L. Abeyawardhane ◽  
Heather R. Lucas
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Iron Homeostasis ◽  
Substantia Nigra Pars Compacta ◽  
Biochemical Alterations ◽  
Redox Active ◽  
Cellular Inclusions ◽  
Iron Redox ◽  
Presynaptic Protein

The etiology of Parkinson’s disease (PD) is linked with cellular inclusions in the substantia nigra pars compacta region of the brain that are enriched in the misfolded presynaptic protein α-synuclein (αS) and death of the dopaminergic neurons. Brain iron homeostasis governs both neurotransmission and neurodegeneration; hence, the role of iron in PD progression and neuronal health is apparent. Elevated iron deposits become prevalent in the cerebral region upon aging and even more so in the PD brain. Structural as well as oxidative modifications can result from coordination of αS with redox active iron, which could have functional and/or pathological implications. In this review, we will discuss iron-mediated αS aggregation, alterations in iron metabolism, and the role of the iron-dopamine couple. Moreover, iron interactions with N-terminally acetylated αS, the physiologically relevant form of the human protein, will be addressed to shed light on the current understanding of protein dynamics and the physiological environment in the disease state. Oxidative pathways and biochemical alterations resulting from aberrant iron-induced chemistry are the principal focus of this review in order to highlight the plethora of research that has uncovered this emerging dichotomy of iron playing both functional and disruptive roles in PD pathology.

Hydrometallurgical thermodynamics. I. Effect of sulfate ion-pairing and ion-solvation on the copper-iron redox equilibrium in aqueous acetonitrile

1983 ◽  
Vol 36 (9) ◽  
pp. 1687 ◽  
Author(s):  
BW Clare ◽  
P Singh ◽  
P Mangano ◽  
AJ Parker ◽  
DM Muir
Keyword(s):  
Water Solution ◽  
Pure Water ◽  
Ion Pairing ◽  
Ion Solvation ◽  
Sulfate Ion ◽  
Redox Equilibrium ◽  
Small Shift ◽  
Enthalpy Changes ◽  
The Right ◽  
Iron Redox

The copper-iron redox equilibrium is shifted to the right CuII+FeII↔CuI+FeIII by strong ion-pairing of sulfate ion with FeIII and by specific solvation of CuI with acetonitrile. The equilibrium constant has been measured by direct e.m.f. and spectroscopic methods between pH 0-2 and found to be about 107 higher for practical solutions of sulfates in acetonitrile/water than that calculated for perchlorates in pure water. Enthalpies and free energies of transfer of these ions from water to acetonitrile/water show that the shift in equilibrium to Cul+FeIII in acetonitrile/water solution is strongly favoured by enthalpy changes associated with copper(I)-acetonitrile ion-solvation. Ion-pairing of sulfate ion with iron(III) results in an increase in entropy and a small shift of the equilibrium to the right.

scholarly journals The Role of the Iron Protoporphyrins Heme and Hematin in the Antimalarial Activity of Endoperoxide Drugs

2022 ◽  
Vol 15 (1) ◽  
pp. 60
Author(s):  
Helenita C. Quadros ◽  
Mariana C. B. Silva ◽  
Diogo R. M. Moreira
Keyword(s):  
Iron Homeostasis ◽  
Antimalarial Activity ◽  
Redox Homeostasis ◽  
Protoporphyrin Ix ◽  
Parasite Survival ◽  
Iron Redox ◽  
Iron Protoporphyrin ◽  
Pharmacological Model ◽  
Peroxide Bond

Plasmodium has evolved to regulate the levels and oxidative states of iron protoporphyrin IX (Fe-PPIX). Antimalarial endoperoxides such as 1,2,4-trioxane artemisinin and 1,2,4-trioxolane arterolane undergo a bioreductive activation step mediated by heme (FeII-PPIX) but not by hematin (FeIII-PPIX), leading to the generation of a radical species. This can alkylate proteins vital for parasite survival and alkylate heme into hematin–drug adducts. Heme alkylation is abundant and accompanied by interconversion from the ferrous to the ferric state, which may induce an imbalance in the iron redox homeostasis. In addition to this, hematin–artemisinin adducts antagonize the spontaneous biomineralization of hematin into hemozoin crystals, differing strikingly from artemisinins, which do not directly suppress hematin biomineralization. These hematin–drug adducts, despite being devoid of the peroxide bond required for radical-induced alkylation, are powerful antiplasmodial agents. This review addresses our current understanding of Fe-PPIX as a bioreductive activator and molecular target. A compelling pharmacological model is that by alkylating heme, endoperoxide drugs can cause an imbalance in the iron homeostasis and that the hematin–drug adducts formed have strong cytocidal effects by possibly reproducing some of the toxifying effects of free Fe-PPIX. The antiplasmodial phenotype and the mode of action of hematin–drug adducts open new possibilities for reconciliating the mechanism of endoperoxide drugs and for malaria intervention.

scholarly journals Peroxiredoxin6 in Endothelial Signaling

Antioxidants ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 63 ◽  
Author(s):  
Priyal Patel ◽  
Shampa Chatterjee
Keyword(s):  
Peroxidase Activity ◽  
Vascular Diseases ◽  
Catalytic Triad ◽  
Cysteine Residue ◽  
Pla2 Activity ◽  
Redox Equilibrium ◽  
Cellular Redox ◽  
Peroxiredoxin 6 ◽  
Injury And Repair

Peroxiredoxins (Prdx) are a ubiquitous family of highly conserved antioxidant enzymes with a cysteine residue that participate in the reduction of peroxides. This family comprises members Prdx1–6, of which Peroxiredoxin 6 (Prdx6) is unique in that it is multifunctional with the ability to neutralize peroxides (peroxidase activity) and to produce reactive oxygen species (ROS) via its phospholipase (PLA2) activity that drives assembly of NADPH oxidase (NOX2). From the crystal structure, a C47 residue is responsible for peroxidase activity while a catalytic triad (S32, H26, and D140) has been identified as the active site for its PLA2 activity. This paradox of being an antioxidant as well as an oxidant generator implies that Prdx6 is a regulator of cellular redox equilibrium (graphical abstract). It also indicates that a fine-tuned regulation of Prdx6 expression and activity is crucial to cellular homeostasis. This is specifically important in the endothelium, where ROS production and signaling are critical players in inflammation, injury, and repair, that collectively signal the onset of vascular diseases. Here we review the role of Prdx6 as a regulator of redox signaling, specifically in the endothelium and in mediating various pathologies.

Role of iron in the interaction of red blood cells with methylglyoxal. Modification of l-arginine by methylglyoxal is catalyzed by iron redox cycling

2001 ◽  
Vol 138 (2) ◽  
pp. 171-187 ◽  
Author(s):  
István Wittmann ◽  
István Mazák ◽  
László Pótó ◽  
Zoltán Wagner ◽  
László Wagner ◽  
...  
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Redox Cycling ◽  
Iron Redox

Iron redox equilibrium, structure and properties of zinc iron phosphate glasses

2007 ◽  
Vol 353 (2) ◽  
pp. 151-158 ◽  
Author(s):  
S.T. Reis ◽  
A. Moguš-Milanković ◽  
V. Ličina ◽  
J.B. Yang ◽  
M. Karabulut ◽  
...  
Keyword(s):  
Iron Phosphate ◽  
Equilibrium Structure ◽  
Phosphate Glasses ◽  
Structure And Properties ◽  
Redox Equilibrium ◽  
Iron Phosphate Glasses ◽  
Iron Redox

Iron Redox Reactions in Model Nuclear Waste Glasses and Melts

2008 ◽  
Vol 1124 ◽  
Author(s):  
Benjamin Cochain ◽  
Daniel R. Neuville ◽  
Jacques Roux ◽  
Dominique De Ligny ◽  
Denis Testemale ◽  
...  
Keyword(s):  
Nuclear Waste ◽  
Oxidation Kinetic ◽  
Limiting Factor ◽  
Redox Equilibrium ◽  
Alkali Cations ◽  
Transition Range ◽  
Nuclear Waste Storage ◽  
Waste Storage ◽  
Redox Kinetics ◽  
Iron Redox

AbstractThe influence of boron on the kinetics of oxidation of iron in silicate melts relevant to nuclear waste storage has been investigated by XANES experiments. The measurements have been performed isothermally as a function of time at the iron K-edge. The redox kinetics become slower with increasing B2O3 content either close to the glass transition range, where the redox kinetics are controlled by diffusion of network-modifying cations, or at superliquidus temperatures where oxygen diffusion is the rate-limiting factor. In both ranges the kinetics can be interpreted in terms of boron speciation and interaction with alkali cations. Below the liquidus, however, the long times needed to reach redox equilibrium allow sintering of the powders investigated to take place so that the resulting changes in sample geometry prevent determinations of oxidation kinetic parameters from being made.

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