Mechanoradical formation and its effects on birch kraft pulp during the preparation of nanofibrillated cellulose with Masuko refining

Holzforschung ◽  
2012 ◽  
Vol 66 (4) ◽  
Author(s):  
Iina Solala ◽  
Aleksander Volperts ◽  
Anna Andersone ◽  
Tatiana Dizhbite ◽  
Nina Mironova-Ulmane ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance Spectroscopy ◽  
Fiber Material ◽  
Nanofibrillated Cellulose ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Pulp Viscosity ◽  
Antioxidant Characteristics ◽  
Birch Kraft Pulp ◽  
Recombination Reactions

AbstractMasuko refining of unbleached kraft birch pulp has been noted to result in more thorough fibrillation than the refining of its bleached counterpart. This result is observed through different fractionation behavior of once refined pulps and is further supported by different relative changes in pulp viscosity. The formation of mechanoradicals during refining is observed with electron paramagnetic resonance spectroscopy, and the role of lignin and hemicelluloses [quantified using kappa number determination and UV resonance Raman (UVRR) spectroscopy] in the progress of refining is discussed. Lignin, a known antioxidant, is capable of stabilizing radicals, which could potentially counteract recombination reactions between highly reactive cellulose radicals. On the other hand, lignin’s ability to promote fibrillation could also lie in its amorphous nature and not solely in its antioxidant characteristics. Furthermore, bleaching removes not only lignin but also hemicelluloses, which affects both the charge density and the structure of the fiber material, and this is another likely contributor to the easier fibrillation of lignin-containing pulps.

Role of Kupffer cells in the pathogenesis of hepatic reperfusion injury

1994 ◽  
Vol 267 (4) ◽  
pp. G630-G636 ◽  
Author(s):  
C. Bremer ◽  
B. U. Bradford ◽  
K. J. Hunt ◽  
K. T. Knecht ◽  
H. D. Connor ◽  
...  
Keyword(s):  
Reperfusion Injury ◽  
Kupffer Cells ◽  
Trypan Blue ◽  
Cell Activation ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Liver Perfusion ◽  
Blue Staining ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance

The purpose of this study was to evaluate the role of Kupffer cell activation in the pathogenesis of reperfusion injury. In a blood-free liver perfusion model, pericentral hypoxia and reperfusion injury occurred. Lactate dehydrogenase (LDH) and malondialdehyde (MDA) release, oxygen uptake, and trypan blue staining were assessed. Within the first 10 min of reflow, LDH and MDA release reached maximal values of 44 U.g-1.h-1 and 115 nmol.g-1.h-1, respectively. Trypan blue cell staining was confined to pericentral regions of the liver lobule. When Kupffer cells were inactivated with GdCl3, release of enzymes and MDA was reduced significantly by > 50%, and hepatic cell death was almost completely absent. Since increases in MDA suggested involvement of free radicals, livers were perfused with phenyl N-t-butylnitrone (5 mM), a spin-trapping agent. Analysis of liver tissue by electron paramagnetic resonance spectroscopy revealed a typical six-line spectrum, providing direct evidence that carbon-centered radicals were generated on reflow. GdCl3 treatment decreased radical adduct formation by approximately 50%. Collectively, these results strongly support the hypothesis that activation of Kupffer cells plays an important role in the pathogenesis of hepatic reperfusion injury.

scholarly journals Tauroursodeoxycholic Acid (TUDCA)—Lipid Interactions and Antioxidant Properties of TUDCA Studied in Model of Photoreceptor Membranes

Membranes ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 327
Author(s):  
Michał J. Sabat ◽  
Anna M. Wiśniewska-Becker ◽  
Michał Markiewicz ◽  
Katarzyna M. Marzec ◽  
Jakub Dybas ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Plasma Membranes ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Protective Action ◽  
Antioxidant Properties ◽  
Model Membranes ◽  
Dynamics Simulation ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Tauroursodeoxycholic Acid

Tauroursodeoxycholic acid (TUDCA), a hydrophilic bile acid containing taurine conjugated with the ursodeoxycholic acid (UDCA), has been known and used from ancient times as a therapeutic compound in traditional Chinese medicine. TUDCA has recently been gaining significant interest as a neuroprotective agent, also exploited in the visual disorders. Among several mechanisms of TUDCA’s protective action, its antioxidant activity and stabilizing effect on mitochondrial and plasma membranes are considered. In this work we investigated antioxidant activity of TUDCA and its impact on structural properties of model membranes of different composition using electron paramagnetic resonance spectroscopy and the spin labeling technique. Localization of TUDCA molecules in a pure POPC bilayer has been studied using a molecular dynamics simulation (MD). The obtained results indicate that TUDCA is not an efficient singlet oxygen (1O2 (1Δg)) quencher, and the determined rate constant of its interaction with 1O2 (1Δg) is only 1.9 × 105 M−1s−1. However, in lipid oxidation process induced by a Fenton reaction, TUDCA reveals substantial antioxidant activity significantly decreasing the rate of oxygen consumption in the system studied. In addition, TUDCA induces slight, but noticeable changes in the polarity and fluidity of the investigated model membranes. The results of performed MD simulation correspond very well with the experimental results.

scholarly journals Ambient base-free glycerol oxidation over bimetallic PdFe/SiO2 by in situ generated active oxygen species

2021 ◽  
Author(s):  
Ricci Underhill ◽  
Mark Douthwaite ◽  
Richard J. Lewis ◽  
Peter J. Miedziak ◽  
Robert D. Armstrong ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Bimetallic Catalyst ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Active Oxygen Species ◽  
Catalytic Performance ◽  
Resonance Spectroscopy ◽  
Oxygen Species ◽  
Paramagnetic Resonance ◽  
Temperature Oxidation

AbstractLow temperature oxidation of alcohols over heterogeneous catalysts is exceptionally challenging, particularly under neutral conditions. Herein, we report on an efficient, base-free method to oxidise glycerol over a 0.5%Pd-0.5%Fe/SiO2 catalyst at ambient temperature in the presence of gaseous H2 and O2. The exceptional catalytic performance was attributed to the in situ formation of highly reactive surface-bound oxygenated species, which promote the dehydrogenation on the alcohol. The PdFe bimetallic catalyst was determined to be significantly more active than corresponding monometallic analogues, highlighting the important role both metals have in this oxidative transformation. Fe leaching was confirmed to occur over the course of the reaction but sequestering experiments, involving the addition of bare carbon to the reactions, confirmed that the reaction was predominantly heterogeneous in nature. Investigations with electron paramagnetic resonance spectroscopy suggested that the reactivity in the early stages was mediated by surface-bound reactive oxygen species; no homogeneous radical species were observed in solution. This theory was further evidenced by a direct H2O2 synthesis study, which confirmed that the presence of Fe in the bimetallic catalyst neither improved the synthesis of H2O2 nor promoted its decomposition over the PdFe/SiO2 catalyst.

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