Catalytic Role of Multinuclear Palladium–Oxygen Intermediates in Aerobic Oxidation Followed by Hydrogen Peroxide Disproportionation

2015 ◽  
Vol 137 (42) ◽  
pp. 13632-13646 ◽  
Author(s):  
Andrew J. Ingram ◽  
Katherine L. Walker ◽  
Richard N. Zare ◽  
Robert M. Waymouth
Keyword(s):  
Hydrogen Peroxide ◽  
Aerobic Oxidation ◽  
Oxygen Intermediates ◽  
Catalytic Role

The role of copper ions in hydrogen peroxide bleaching: Their origin, removal, and effect on pulp quality

TAPPI Journal ◽  
2012 ◽  
Vol 11 (7) ◽  
pp. 37-46 ◽  
Author(s):  
PEDRO E.G. LOUREIRO ◽  
SANDRINE DUARTE ◽  
DMITRY V. EVTUGUIN ◽  
M. GRAÇA V.S. CARVALHO
Keyword(s):  
Hydrogen Peroxide ◽  
Copper Ions ◽  
Peroxide Bleaching ◽  
Metals Removal ◽  
Peroxide Decomposition ◽  
Equipment Corrosion ◽  
And Performance ◽  
And Control ◽  
Main Effects

This study puts particular emphasis on the role of copper ions in the performance of hydrogen peroxide bleaching (P-stage). Owing to their variable levels across the bleaching line due to washing filtrates, bleaching reagents, and equipment corrosion, these ions can play a major role in hydrogen peroxide decomposition and be detrimental to polysaccharide integrity. In this study, a Cu-contaminated D0(EOP)D1 prebleached pulp was subjected to an acidic washing (A-stage) or chelation (Q-stage) before the alkaline P-stage. The objective was to understand the isolated and combined role of copper ions in peroxide bleaching performance. By applying an experimental design, it was possible to identify the main effects of the pretreatment variables on the extent of metals removal and performance of the P-stage. The acid treatment was unsuccessful in terms of complete copper removal, magnesium preservation, and control of hydrogen peroxide consumption in the following P-stage. Increasing reaction temperature and time of the acidic A-stage improved the brightness stability of the D0(EOP)D1AP bleached pulp. The optimum conditions for chelation pretreatment to maximize the brightness gains obtained in the subsequent P-stage with the lowest peroxide consumption were 0.4% diethylenetriaminepentaacetic acid (DTPA), 80ºC, and 4.5 pH.

An ESR study of the peroxidase reaction catalyzed by human methaemoglobin and methaemoglobin-haptoglobin complex

1991 ◽  
Vol 56 (4) ◽  
pp. 923-932
Author(s):  
Jana Stejskalová ◽  
Pavel Stopka ◽  
Zdeněk Pavlíček
Keyword(s):  
Hydrogen Peroxide ◽  
Ascorbic Acid ◽  
Amino Acid ◽  
Peroxidase Activity ◽  
Amino Acid Analysis ◽  
Superoxide Radical ◽  
Esr Spectra ◽  
The Other ◽  
Delocalized Electron

The ESR spectra of peroxidase systems of methaemoglobin-ascorbic acid-hydrogen peroxide and methaemoglobin-haptoglobin complex-ascorbic acid-hydrogen peroxide have been measured in the acetate buffer of pH 4.5. For the system with methaemoglobin an asymmetrical signal with g ~ 2 has been observed which is interpreted as the perpendicular region of anisotropic spectrum of superoxide radical. On the other hand, for the system with methaemoglobin-haptoglobin complex the observed signal with g ~ 2 is symmetrical and is interpreted as a signal of delocalized electron. After realization of three repeatedly induced peroxidase processes the ESR signal of the perpendicular part of anisotropic spectrum of superoxide radical is distinctly diminished, whereas the signal of delocalized electron remains practically unchanged. An amino acid analysis of methaemoglobin along with results of the ESR measurements make it possible to derive a hypothesis about the role of haptoglobin in increasing of the peroxidase activity of methaemoglobin.

Inhibition of the water channel aquaporin-1 prevents myocardial remodeling by blocking the transmembrane transport of hydrogen peroxide

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
V Montiel ◽  
R Bella ◽  
L Michel ◽  
E Robinson ◽  
J.C Jonas ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Cardiac Hypertrophy ◽  
Cardiac Myocytes ◽  
Cardiac Remodeling ◽  
Cardiac Myocyte ◽  
Water Channel ◽  
Transmembrane Transport ◽  
Funding Source ◽  
Water Pore

Abstract Background Pathological remodeling of the myocardium has long been known to involve oxidant signaling, but so far, strategies using systemic anti-oxidants have generally failed to prevent it. Aquaporins are a family of transmembrane water channels with thirteen isoforms currently known. Some isoforms have been implicated in oxidant signaling. AQP1 is the most abundant aquaporin in cardiovascular tissues but its specific role in cardiac remodeling remains unknown. Purpose We tested the role of AQP1 as a key regulator of oxidant-mediated cardiac remodeling amenable to targeted pharmacological therapy. Methods We used mice with genetic deletion of Aqp1 (and wild-type littermate), as well as primary isolates from the same mice and human iPSC/Engineered Heart Tissue to test the role of AQP1 in pro-hypertrophic signaling. Human cardiac myocyte-specific (PCM1+) expression of AQP's and genes involved in hypertrophic remodeling was studied by RNAseq and bioinformatic GO pathway analysis. Results RNA sequencing from human cardiac myocytes revealed that the archetypal AQP1 is a major isoform. AQP1 expression correlates with the severity of hypertrophic remodeling in patients with aortic stenosis. The AQP1 channel was detected at the plasma membrane of human and mouse cardiac myocytes from hypertrophic hearts, where it colocalizes with the NADPH oxidase-2 (NOX2) and caveolin-3. We show that hydrogen peroxide (H2O2), produced extracellularly, is necessary for the hypertrophic response of isolated cardiac myocytes and that AQP1 facilitates the transmembrane transport of H2O2 through its water pore, resulting in activation of oxidant-sensitive kinases in cardiac myocytes. Structural analysis of the amino acid residues lining the water pore of AQP1 supports its permeation by H2O2. Deletion of Aqp1 or selective blockade of AQP1 intra-subunit pore (with Bacopaside II) inhibits H2O2 transport in mouse and human cells and rescues the myocyte hypertrophy in human induced pluripotent stem cell-derived engineered heart muscle. This protective effect is due to loss of transmembrane transport of H2O2, but not water, through the intra-subunit pore of AQP1. Treatment of mice with clinically-approved Bacopaside extract (CDRI08) inhibitor of AQP1 attenuates cardiac hypertrophy and fibrosis. Conclusion We provide the first demonstration that AQP1 functions as an aqua-peroxiporin in primary rodent and human cardiac parenchymal cells. We show that cardiac hypertrophy is mediated by the transmembrane transport of H2O2 through the AQP1 water channel. Our studies open the way to complement the therapeutic armamentarium with specific blockers of AQP1 for the prevention of adverse remodeling in many cardiovascular diseases leading to heart failure. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): FRS-FNRS, Welbio

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