Topic
Oxygen
About: Oxygen is a research topic. Over the lifetime, 48149 publications have been published within this topic receiving 1113788 citations. The topic is also known as: O & Oxygen.
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TL;DR: The findings show that the oxygen atoms of the hydroxyl group at C-11 and of the keto group atC-9 originate in the same molecule of oxygen.
Abstract: Prostaglandin E1 was synthesized by incubating 81114-eicosatrienoic acid with a proportion of vesicular gland for 10 minutes in an atmosphere of labeled oxygen. To determine the origin of the oxygens of the ring a derivative was oxidized by permanganate-periodate and analyzed by mass spectrometry. The findings show that the oxygen atoms of the hydroxyl group at C-11 and of the keto group at C-9 originate in the same molecule of oxygen. Two distinct reactions are involved in this transformation: a dioxygenase and a monooxygenase reaction. Dioxygenation probably occurs by the addition of oxygen across carbons 9 and 11 with concomitant ring closure between carbons 8 and 12 involving a conrotatory process. Conversion to prostaglandin E1 also involves isomerization of a double bond and introduction of a hydroxyl group at C-15. Another mechanism involved may be the formatiom of a hydroperoxide at C-11 with isomerization of a double bond. Further studies should be done to determine whether or not the introduction of the oxygens at C-9 and C-11 precedes the introduction of oxygen at C-15.
210 citations
TL;DR: In this article, it was shown that only the outer surface of the oxide electrode participates in the oxygen evolution reaction, which is an indication that the IrO 2 layers participate in the reaction in acid media at least to a several monolayer extend.
210 citations
TL;DR: In this article, the authors reviewed several reactions pertinent to remediating contaminated groundwaters via hydrogen peroxide (H2O2) addition, including microbial catalase and several inorganic catalysts such as iron oxide species.
210 citations
TL;DR: A spectroreflectometric technique was used to determine the relative percentages of three myoglobin pigments, reduced myoglobin, oxymyoglobin and metmyoglobin at the surface of fresh beef and it was shown that, at constant humidity, the formation of meetmyoglobin in beef was maximal at 6 + 3 mm Hg of oxygen.
Abstract: SUMMARY: A spectroreflectometric technique was used to determine the relative percentages of three myoglobin pigments, reduced myoglobin, oxymyoglobin and metmyoglobin at the surface of fresh beef. It was shown that, at constant humidity, the formation of metmyoglobin in beef was maximal at 6 + 3 mm Hg of oxygen at 0°C and 7.5 ± 3 mm Hg at 7°C for semitendinosus muscles. Carbon dioxide concentrations of 10% and higher had negligible effect on the formation of metmyoglobin, provided the oxygen pressure was above about 5%. At high partial pressures of carbon dioxide, absorption of carbon dioxide increased and the pH of the surface decreased. In air, the formation of metmyoglobin varied widely from muscle to muscle.
210 citations
TL;DR: A novel oxygen microelectrode with a tip diameter of 2 to 20 mum was constructed which could function satisfactorily under a variety of environmental conditions and in a range of media, including human blood serum, citric acid at pH 2.5, moist air, and paraffin oil.
Abstract: A novel oxygen microelectrode with a tip diameter of 2 to 20 μm was constructed which could function satisfactorily under a variety of environmental conditions and in a variety of media, including human blood serum, citric acid at pH 2.5, moist air, and paraffin oil. Measurement of oxygen by this electrode does not require stirring of the medium. Electrodes could be made so that the 90% response time necessary to detect changes in oxygen concentration was less than 0.2 s, and response was linear with oxygen concentration. To demonstrate the performance of the electrode, oxygen and photosynthesis profiles of an acid microbial mat (pH 2.8) dominated by the eucaryotic alga Cyanidium caldarium were made. Photosynthetic rates as high as 95 mmol of O2 dm−3 h−1 were measured within the most active 0.1-mm layer, which was ca. 0.2 mm below the surface of the microbial mat. The total photosynthetic activity was 47 mmol of O2 m−2 h−1. Vertical profiles of photosynthesis at different light intensities showed that the microalgae within the mat were not photoinhibited at bright sunlight (2,090 μEinsteins m−2 s−1).
209 citations