Peroxide in the context of "Lipid peroxidation"

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

The sulfate or sulphate ion is a polyatomic anion with the empirical formula SO₄. Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many are prepared from that acid.

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.

Firefly luciferin (also known as beetle luciferin) is the luciferin, precursor of the light-emitting compound, used for the firefly (Lampyridae), railroad worm (Phengodidae), starworm (Rhagophthalmidae), and click-beetle (Pyrophorini) bioluminescent systems. It is the substrate of firefly luciferase (EC 1.13.12.7), which is responsible for the characteristic light emission of many firefly and other insect species in the visible spectra ranging from 530 until 630 nm.

As with other luciferins, oxygen is essential for the luminescence mechanism, which involves the decomposition of a cyclic peroxide to produce excited-state molecules capable of emitting light as they relax to the ground state. Additionally, it has been found that adenosine triphosphate (ATP) and magnesium are required for light emission.

Organic peroxides are organic compounds containing the peroxide functional group (R−O−O−R′). If the R′ is hydrogen, the compounds are called hydroperoxides, which are discussed in that article. The O−O bond of peroxides easily breaks, producing free radicals of the form RO (the dot represents an unpaired electron). Thus, organic peroxides are useful in organic chemistry as initiators for some types of polymerization, such as the acrylic, unsaturated polyester, and vinyl ester resins used in glass-reinforced plastics. MEKP and benzoyl peroxide are commonly used for this purpose. However, the same property also means that organic peroxides can explosively combust. Organic peroxides, like their inorganic counterparts, are often powerful bleaching agents.

An inorganic peroxide is a peroxide of an inorganic compound. Metal peroxides are metal-containing peroxides with ionically- or covalently-bonded peroxide (O2−2) groups. This large family of compounds can be divided into ionic and covalent peroxide. The first class mostly contains the peroxides of the alkali and alkaline earth metals whereas the covalent peroxides are represented by such compounds as hydrogen peroxide and peroxymonosulfuric acid (H₂SO₅). In contrast to the purely ionic character of alkali metal peroxides, peroxides of transition metals have a more covalent character.

Main group peroxides are peroxide derivatives of the main group elements (many of which are metals). Many compounds of the main group elements form peroxides, and a few are of commercial significance.

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.