Superoxide in the context of "Superoxide dismutase"

The alkali metals react with oxygen to form several different compounds: suboxides, oxides, peroxides, sesquioxides, superoxides, and ozonides. They all react violently with water.

A sesquioxide is an oxide of an element (or radical), where the ratio between the number of atoms of that element and the number of atoms of oxygen is 2:3. For example, aluminium oxide Al₂O₃ and phosphorus(III) oxide P₄O₆ are sesquioxides.Many sesquioxides contain a metal in the +3 oxidation state and the oxide ion O, e.g., aluminium oxide Al₂O₃, lanthanum(III) oxide La₂O₃ and iron(III) oxide Fe₂O₃. Sesquioxides of iron and aluminium are found in soil. The alkali metal sesquioxides are exceptions because they contain both peroxide O2−2 and superoxide O−2 ions, e.g., rubidium sesquioxide Rb₄O₆ is formulated (Rb)₄(O2−2)(O−2)₂. Sesquioxides of metalloids and nonmetals are better formulated as covalent, e.g. boron trioxide B₂O₃, dinitrogen trioxide N₂O₃ and phosphorus(III) oxide P₄O₆; chlorine trioxide Cl₂O₃ and bromine trioxide Br₂O₃ do not have oxidation state +3 on the halogen.

Many transition metal oxides crystallize in the corundum structure type, with space group R3c. Sesquioxides of rare earth elements crystalize into one or more of three crystal structures: hexagonal (type A, space group P3m1), monoclinic (type B, space group C2/m), or body-centered cubic (type C, space group Ia3).

Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological system's ability to readily detoxify the reactive intermediates or to repair the resulting damage. Disturbances in the normal redox state of cells can cause toxic effects through the production of peroxides and free radicals that damage all components of the cell, including proteins, lipids, and DNA. Oxidative stress from oxidative metabolism causes base damage, as well as strand breaks in DNA. Base damage is mostly indirect and caused by the reactive oxygen species generated, e.g., O
₂ (superoxide radical), OH (hydroxyl radical) and H₂O₂ (hydrogen peroxide). Further, some reactive oxidative species act as cellular messengers in redox signaling. Thus, oxidative stress can cause disruptions in normal mechanisms of cellular signaling.

In humans, oxidative stress is thought to be involved in the development of cancer, Parkinson's disease, Lafora disease, Alzheimer's disease, atherosclerosis, heart failure, myocardial infarction, fragile X syndrome, sickle-cell disease, lichen planus, vitiligo, infection, chronic fatigue syndrome, and depression; however, reactive oxygen species can be beneficial, as they are used by the immune system as a way to attack and kill pathogens. Oxidative stress due to noise was estimated at cell level using model of growing lymphocytes. Exposure of sound with frequency 1 KHz and intensity 110 dBA for 4 hours and eight hours per day may induce oxidative stress in growing lymphocytes causing the difference in viable cell count. However the catalase activity depends on duration of exposure. In case of noise exposure of 8 hours per day, it declines significantly as compared to noise exposure of 4 hours per day.

Pyrazine is a heterocyclic aromatic organic compound with the chemical formula C₄H₄N₂. It is a symmetrical molecule with point group D_2h. Pyrazine is less basic than pyridine, pyridazine and pyrimidine. It is a "deliquescent crystal or wax-like solid with a pungent, sweet, corn-like, nutty odour".

Pyrazine and a variety of alkylpyrazines are flavor and aroma compounds found in baked and roasted goods. Tetramethylpyrazine (also known as ligustrazine) is reported to scavenge superoxide anions and decrease nitric oxide production in human granulocytes.

Potassium superoxide is an inorganic compound with the formula KO₂. It is a yellow paramagnetic solid that decomposes in moist air. It is a rare example of a stable salt of the superoxide anion. It is used as a CO₂ scrubber, H₂O dehumidifier, and O₂ generator in rebreathers, spacecraft, submarines, and spacesuits.

Rubidium sesquioxide is a chemical compound with the formula Rb₂O₃ or more accurately Rb₄O₆. In terms of oxidation states, Rubidium in this compound has a nominal charge of +1, and the oxygen is a mixed peroxide (O2−2) and superoxide (O−2) for a structural formula of (Rb)₄(O−2)₂(O2−2). It has been studied theoretically as an example of a strongly correlated material.

The compound was predicted to be a rare example of a ferromagnetic compound that is magnetic due to a p-block element, and a half-metal that was conducting in the minority spin band. However, while the material does have exotic magnetic behavior, experimental results instead showed an electrically insulating magnetically frustrated system. Rb₄O₆ also displays a Verwey transition where charge ordering appears at 290 K.

In chemistry and biology, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (O₂), water, and hydrogen peroxide. Some prominent ROS are hydroperoxide, superoxide (O₂), hydroxyl radical (OH), and singlet oxygen(O₂). ROS are pervasive because they are readily produced from O₂, which is abundant. ROS are important in many ways, both beneficial and otherwise. ROS function as signals, that turn on and off biological functions. They are intermediates in the redox behavior of O₂, which is central to fuel cells. ROS are central to the photodegradation of organic pollutants in the atmosphere. Most often, however, ROS are discussed in a biological context, ranging from their effects on aging and their role in causing dangerous genetic mutations.