High valent iron-oxo species are often invoked as the key oxidizing agents in the catalytic cycles of oxygen activating nonheme iron enzymes, and three of these intermediates have in fact been characterized.
The observation that Mps1- and Polo-associated filaments reappear in the same locations through multiple cycles of oxygen deprivation demonstrates that underlying structural components of the filaments must still be present during normoxic conditions.
If sulfur is added to the culture once hydrogen production has ceased, the cells, and particularly PSII, can repair; cycles of oxygen production under S-sufficiency and H2 production under S-deprivation can result (e.g., Ghirardi et al., 2000).
Oxygen cycle, circulation of oxygen in various forms through nature.
SDB is caused by the repeated collapse of the upper airway during sleep, which results in a cycle of inadequate oxygen intake and arousal from sleep.
This de novo cytochrome is capable of reversible oxygen binding, an obligate step in the catalytic cycle of many oxygen-activating oxidoreductases.
These are thought to be the cause of cycles of low oxygen tension with subsequent reoxygenation, a phenomenon known as cycling (or fluctuating) hypoxia (Chaplin et al, 1987; Kimura et al, 1996; Matsumoto et al, 2010).
A scaling-based, data-driven empirical model was developed for robust predictions of the diurnal cycle of stream dissolved oxygen (DO) by utilizing a single reference observation as the scaling parameter.
This biogeochemical cycle describes the movement of oxygen within and between its three main reservoirs on Earth: the atmosphere, the biosphere, and the lithosphere.
In respiratory species, such as the dairy yeast Kluyveromyces lactis and the filamentous fungus Ashbya gossypii, pyruvate is fully oxidized to CO2 and H2O in mitochondria through the tricarboxylic acid (TCA) cycle in the presence of oxygen, and the free energy released in this process is stored in ATPs by oxidative phosphorylation.
