Reactive oxygen species silica

In addition to the QM structure of the natural terpene QMs, the reactive oxygen species (ROS) may also play a significant role in the observed biological activities. In the synthesis of taxodione and taxodone, QMs were formed from the catechol precursors through the spontaneous oxidation in the presence of silica gel.7, 8,49-51... 

B. Fubini, I. Fenoglio, Z. Elias, and O. Poirot, On the Variability of the Biological Responses to Silicas Effect of Origin, Crystallinity and State of the Surface on the Generation of Reactive Oxygen Species and Consequent Morphological Transformations in Cells, J. Environ. Pathol. Toxicol. Oncol. 20, 87-100 (2001). 

Shi X., Ding M., Chen F., Wang L., Rojanasakul Y., Vallyathan V., and Castranova V. (2001) Reactive oxygen species and molecular mechanisms of silica-induced lung injury. J. Environ. Pathol. Toxicol. Oncol. 20(suppl. 1), 85-93. 

Deshpande, A., Narayanan, P.K., and Lehnert, B.E., Silica-induced generation of extracellular factor(s) increases reactive oxygen species in human bronchial epithelial cells, Toxicol Sci., 67,... 

Shen, H.M., Zhang, Z., Zhang, Q.F., and Ong, C.N., Reactive oxygen species and caspase activation mediate silica-induced apoptosis in alveolar macrophages. Am. J. Physiol. Lung Cell. Mol. Physiol, 280, LI0-17, 2001. 

A number of studies [18] submission of information on in vitro and in vivo toxicity of silica nanoparticles - both crystalline and amorphous. Most of the results on the toxicity in vitro is reduced to the analysis of size - and dose-dependent cytotoxicity, increased reactive oxygen species and proinflammatory stimulation. The data obtained from in vivo studies demonstrate nanoparticles induced lung inflammation and fibrosis, emphysema, and granuloma formation. It is therefore important to monitor the content of nano-sized silica in the body. 

While Ray et al. (1951) did not find any inhibitory effect on the action of quartz by anthracite and coal mine dusts mixed with quartz when introduced by intratracheal instillation in the lungs of rats, Rehn et al. (1995) raised the question whether the formation of reactive oxygen species by macrophages engulfing coal mine dust containing free silica could be depressed by the coal part. 

Starting with the formation of reactive oxygen species and followed by caspase-9 and caspase-3 activation, poly(ADP-ribose)polymerase clevage and DNA fragmentation. Silica-induced apoptosis was significantly attenuated by a caspase-3 inhibitor, N-acetyl-Asp-Glu-Val-Asp aldehyde, and ebselen (formula [65]). 

Various Pd based catalysts supported on silica and containing manganese have been prepared and characterized. Two Mn species have been detected, i) reduced Mn in direct interaction with Pd on the metallic particles ii) oxidised Mn layed on Si02 and showing reactive oxygens An increase in activity for reduction of NO is observed on the catalysts containing Mn with an optimum for a Pd/Mn atomic ratio of about one. This enhancement of activity is due to either the presence of Pd-Mn dual sites or to a bifiinctional mechanism between reduced Pd and oxidised Mn at the vicinity of Pd. 

Abstract Plasma polymerization is a technique for modifying the surface characteristics of fillers and curatives for rubber from essentially polar to nonpolar. Acetylene, thiophene, and pyrrole are employed to modify silica and carbon black reinforcing fillers. Silica is easy to modify because its surface contains siloxane and silanol species. On carbon black, only a limited amount of plasma deposition takes place, due to its nonreactive nature. Oxidized gas blacks, with larger oxygen functionality, and particularly carbon black left over from fullerene production, show substantial plasma deposition. Also, carbon/silica dual-phase fillers react well because the silica content is reactive. Elemental sulfur, the well-known vulcanization agent for rubbers, can also be modified reasonably well. 

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