In chemistry, radicals (often referred to as free radicals) are atomic or molecular species with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly reactive, so radicals are likely to take part in chemical reactions. Radicals play an important role in combustion, atmospheric chemistry, polymerization, plasma chemistry, biochemistry, and many other chemical processes, including human physiology. For example, superoxide and nitric oxide regulate many biological processes, such as controlling vascular tone. "Radical" and "free radical" are frequently used interchangeably, however a radical may be trapped within a solvent cage or be otherwise bound. The first organic free radical, the triphenylmethyl radical was identified by Moses Gomberg in 1900 at the University of Michigan. For other uses, see Chemistry (disambiguation). ... Properties For other meanings of Atom, see Atom (disambiguation). ... In science, a molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... For other uses, see Electron (disambiguation). ... In the context of atomic orbitals, an open shell is a valence shell which is not completely filled with electrons or which has not given all of its valence electrons through chemical bonds with other atoms or molecules during a chemical reaction. ... For other uses, see Chemical reaction (disambiguation). ... This article is about the chemical reaction combustion. ... Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earths atmosphere and that of other planets is studied. ... An example of alkene polymerisation, in which each Styrene monomer units double bond reforms as a single bond with another styrene monomer and forms polystyrene. ... For other uses, see Plasma. ... Biochemistry (from Greek: , bios, life and Egyptian kÄ“me, earth[1]) is the study of the chemical processes in living organisms. ... Lewis electron configuration of superoxide. ... R-phrases , , , , S-phrases , , , Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Nitric oxide or Nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of... Cage Effect (chemistry) The cage effect in chemistry describes how properties of a molecule are affected by its surrounding. ... The triphenylmethyl radical is a persistent radical and the first ever radical described in organic chemistry. ... Moses Gomberg, the father of radical chemistry Moses Gomberg (1866–1947) was a chemist. ... The University of Michigan, Ann Arbor (U of M, UM or simply Michigan) is a coeducational public research university in the state of Michigan. ...

Historically, the term radical has also been used for bound parts of the molecule, especially when they remain unchanged in reactions. For example, methyl alcohol was described as consisting of a methyl 'radical' and a hydroxyl 'radical'. Neither were radicals in the usual chemical sense, as they were permanently bound to each other, and had no unpaired, reactive electrons. In mass spectrometry, such radicals are observed after breaking down the substance with a hail of energetic electrons. Mass spectrometry (previously called mass spectroscopy (deprecated)[1] or informally, mass-spec and MS) is an analytical technique used to measure the mass-to-charge ratio of ions. ...

Moses Gomberg (1866-1947)

Image File history File links Moses Gomberg File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Moses Gomberg File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...

Depicting radicals in chemical reactions

In written chemical equations, free radicals are frequently denoted by a dot placed immediately to the right of the atomic symbol or molecular formula as follows:

Chlorine gas can be broken down by ultraviolet light to form atomic chlorine radicals.

Radical reaction mechanisms use single-headed arrows to depict the movement of single electrons: In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs. ...

The homolytic cleavage of the breaking bond is drawn with a 'fish-hook' arrow to distinguish from the usual movement of two electrons depicted by a standard curly arrow. It should be noted that the second electron of the breaking bond also moves to pair up with the attacking radical electron; this is not explicitly indicated in this case. Image File history File links No higher resolution available. ... In chemistry, homolysis is chemical bond dissociation of a neutral molecule generating two free radicals. ...

In chemistry, free radicals take part in radical addition and radical substitution as reactive intermediates. Chain reactions involving free radicals can usually be divided into three distinct processes: initiation, propagation, and termination. In Organic chemistry, a radical addition reaction is an addition reaction in which the first species that adds is a radical. ... In Organic chemistry, a radical substitution reaction is a substitution reaction where a radical is the intermediate and the product is an alkyl halide. ... In chemistry a reactive intermediate is a short-lived high energy highly reactive molecule. ...

• Initiation reactions are those which result in a net increase in the number of free radicals. They may involve the formation of free radicals from stable species as in Reaction 1 above or they may involve reactions of free radicals with stable species to form more free radicals.
• Propagation reactions are those reactions involving free radicals in which the total number of free radicals remains the same.
• Termination reactions are those reactions resulting in a net decrease in the number of free radicals. Typically two free radicals combine to form a more stable species, for example: 2Cl·→ Cl₂

Formation

Radicals may occur naturally as relatively stable chemical compounds. The most common example is molecular dioxygen O₂, which in its stable ground state has two unpaired electrons.

The formation of radicals may involve breaking of covalent bonds homolytically, a process that requires significant amounts of energy. For example, splitting H₂ into 2H· has a ΔH° of +435 kJ/mol, and Cl₂ into 2Cl· has a ΔH° of +243 kJ/mol. This is known as the homolytic bond dissociation energy, and is usually abbreviated as the symbol DH°. The bond energy between two covalently bonded atoms is affected by the structure of the molecule as a whole, not just the identity of the two atoms, and radicals requiring more energy to form are less stable than those requiring less energy. Homolytic bond cleavage most often happens between two atoms of similar electronegativity. In organic chemistry this is often the O-O bond in peroxide species or O-N bonds. In chemistry, homolysis is chemical bond dissociation of a neutral molecule generating two free radicals. ... In chemistry, bond dissociation energy, D0, is one measure of the bond strength in a chemical bond. ... The general structure of an organic peroxide. ...

However, propagation is a very exothermic reaction. Note that most species are electrically neutral although radical ions do exist. In chemistry, an exothermic reaction is one that releases heat . ... A radical ion is a free radical species that carries a charge. ...

Radicals may also be formed by single electron oxidation or reduction of an atom or molecule. An example is the production of superoxide by the electron transport chain. The most fundamental reactions in chemistry are the redox processes. ... Reduction or reducing has several meanings: In mathematics, reduction is the process of manipulating a series of equations or matrices into a desired simpler format. ... Lewis electron configuration of superoxide. ... The Electron Transport Chain. ...

Persistence and stability

The radical derived from α-tocopherol

Long lived radicals can be placed into two categories Image File history File links VitE.gif Licensing File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...

• Stable Radicals

The prime example of a stable radical is molecular dioxygen O₂. Organic radicals can be long lived if they occur in a conjugated π system, such as the radical derived from α-tocopherol (vitamin E). Albeit there exist hundreds of known examples of thiazyl radicals which show remarkable kinetic and thermodynamic stability, with only a very limited extent of π resonance stabilization ^[1].

• Persistent Radicals

Persistent radical compounds are those whose longevity is due to steric crowding around the radical center and makes it physically difficult for the radical to react with another molecule. Examples of these include Gomberg's triphenylmethyl radical, Fremy's salt (Potassium nitrosodisulfonate, (KSO₃)₂NO·), nitroxides, (general formula R₂NO·) such as TEMPO, verdazyls, nitronyl nitroxides, and azephenylenyls. The longest-lived free radical is melanin, which may persist for millions of years.

• Diradicals are molecules containing two radical centers. Multiple radical centers can exist in a molecule. In fact, much to the surprise of many, molecular oxygen naturally (i.e. atmospheric dioxygen) exists as a diradical (in its ground state as triplet oxygen). The high reactivity of atmospheric oxygen is owed somewhat to its diradical state (albeit non-radical states of dioxygen are actually less stable). The existence of atmospheric molecular oxygen as a triplet-state genuine radical results in its paramagnetic character, which can be easily demonstrated, i.e. by attraction of oxygen to an external magnet. (Note however that paramagnetism does not necessarily imply radical character.)

Tocopherol, or Vitamin E, is a fat-soluble vitamin in eight forms that is an important antioxidant. ... Tetrasulfur tetranitride is an inorganic compound with the formula S4N4. ... Resonance in chemistry is a tool used (predominately in organic chemistry) to represent certain types of molecular structures. ... The triphenylmethyl radical is a persistent radical and the first ever radical described in organic chemistry. ... Fremys salt discovered in 1845 by Edmond Fremy (1814 - 1894) is a chemical compound and a strong oxidizing agent. ... An amine oxide, also known as amine-N-oxide and N-oxide, is a chemical compound that contains the functional group R3N+-O− (sometimes written as R3N=O or R3N→O). ... For other uses, see Tempo (disambiguation). ... Broadly, melanin is any of the polyacetylene, polyaniline, and polypyrrole blacks and browns or their mixed copolymers. ... Wikipedia does not have an article with this exact name. ... Simple Illustration of a paramagnetic probe made up from miniature magnets. ...

Reactivity

Radical alkyl intermediates are stabilized by similar criteria as carbocations: the more substituted the radical center is, the more stable it is. This will direct their reactions: formation of a tertiary radical (R₃C·) is favored over secondary (R₂HC·) or primary (RH₂C·). However, radicals next to functional groups, such as carbonyl, nitrile, and ether are even more stable than tertiary alkyl radicals. A carbocation (pronounced carbo-cat-ion) is an ion with a positively-charged carbon atom. ...

Radicals attack double bonds, but unlike similar ions, they are slightly less directed by electrostatic interactions. For example, the reactivity of nucleophilic ions with α,β-unsaturated compounds (C=C-C=O) is directed by the electron-withdrawing effect of the oxygen, resulting in a partial positive charge on the carbonyl carbon. There are two reactions that are observed in the ionic case: the carbonyl is attacked in a direct addition to carbonyl, or the vinyl is attacked in conjugate addition, and in either case, the charge on the nucleophile is taken by the oxygen. Radicals add rapidly to the double bond, and the resulting α-radical carbonyl is relatively stable. Nonetheless, the electrophilic/neutrophilic character of radicals has been shown in a variety of instances (e.g., in the alternating tendency of the copolymerization of malieic anhydride (electrophilic) and styrene (slightly nuecleophilic). Nucleophilic conjugate addition Nucleophilic conjugate addition is a type of organic reaction. ...

In intramolecular reactions, precise control can be achieved despite the extreme reactivity of radicals. Radicals will attack the closest reactive site the most readily. Therefore, when there is a choice, a preference for five-membered rings is observed: four-membered rings are too strained, and collisions with carbons five or more atoms away in the chain are infrequent.

Combustion

Spectrum of the blue flame from a butane torch showing excited molecular radical band emission and Swan bands.

Probably the most familiar free-radical reaction for most people is combustion. The oxygen molecule is a stable diradical, best represented by ·O-O·, which is stable because the spins of the electrons are parallel. The ground state of oxygen is an unreactive spin-paired (triplet) radical, but an extremely reactive spin-unpaired (singlet) radical is available. In order for combustion to occur, the energy barrier between these must be overcome. This barrier can be overcome by heat, requiring high temperatures, or can be lowered by enzymes to initiate reactions at the temperatures inside living things. Image File history File links Download high-resolution version (3950x2739, 411 KB)[edit] Summary Spectrum of a blue flame from a pocket butane torch clearly showing non-continuum spectral emission. ... Image File history File links Download high-resolution version (3950x2739, 411 KB)[edit] Summary Spectrum of a blue flame from a pocket butane torch clearly showing non-continuum spectral emission. ... Butane, also called n-butane, is the unbranched alkane with four carbon atoms, CH3CH2CH2CH3. ... Spectrum of the blue flame from a butane torch showing excited molecular radical band emission and Swan bands. ... This article is about the chemical reaction combustion. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ... Wikipedia does not have an article with this exact name. ... In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ... In physics, the ground state of a quantum mechanical system is its lowest-energy state. ... Triplet oxygen is the ground state of the oxygen molecule. ... Molecular orbital diagram for singlet oxygen. ... The sparks generated by striking steel against a flint provide the activation energy to initiate combustion in this Bunsen burner. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ...

Combustion is comprised of various radical chain reactions that the singlet radical can initiate. The flammability of a given material is strongly dependent on the concentration of free radicals that must be obtained before initiation and propagation reactions dominate leading to combustion of the material. Once the combustible material has been consumed, termination reactions again dominate and the flame dies out. Propagation or termination reactions can be promoted to alter flammability. Tetraethyl lead was once commonly added to gasoline, because it very easily breaks up into radicals, which consume other free radicals in the gasoline-air mixture. This prevents the combustion from initiating prematurely (see engine knock). A hazard warning symbol for flammable chemicals Flammable liquid warning sign Flammability is the ease with which a substance will ignite, causing fire or combustion. ... Tetra-ethyl lead (also known as TEL, lead tetraethyl and tetraethyllead) is a toxic organometallic chemical compound, with formula (CH2CH3)4Pb, which was once used as a gasoline (petrol) additive. ... Knocking (also called pinking or pinging)— colloquially detonation—in internal combustion engines occurs when air/fuel mixture in the cylinder detonates or ignites prior to the timed pre-set conditions in the engines cylinder(s). ...

Polymerization

In addition to combustion, many polymerization reactions involve free radicals. As a result many plastics, enamels, and other polymers are formed through radical polymerization. An example of alkene polymerisation, in which each Styrene monomer units double bond reforms as a single bond with another styrene monomer and forms polystyrene. ... Radical polymerization is a type of polymerization in which the propagation head of a polymer chain consists of a radical. ...

Recent advances in radical polymerization methods, known as Living Radical Polymerization, include: In polymer chemistry, living polymerization is a form of addition polymerization where the ability of a growing polymer chain to terminate has been removed . ...

• Reversible Addition-Fragmentation chain Transfer (RAFT)
• Atom Transfer Radical Polymerization (ATRP)
• Nitroxide Mediated Polymerization (NMP)

These methods produce polymers with a much narrower distribution of molecular weights. RAFT or Reversible Addition-Fragmentation chain Transfer is a form of living radical polymerization. ... ATRP or Atom Transfer Radical Polymerization is a polymerization reaction involving free radicals. ...

Atmospheric radicals

The most common radical in the lower atmosphere is molecular dioxygen. In the upper atmosphere free radicals are produced through photodissociation of the source molecules, particularly the normally unreactive chlorofluorocarbons by solar ultraviolet radiation or by reactions with other stratospheric constituents. These free radicals then react with ozone in a catalytic chain reaction which destroys the ozone, but regenerates the free radical, allowing it to participate in additional reactions. Such reactions are believed to be the primary cause of depletion of the ozone layer and this is why the use of chlorofluorocarbons as refrigerants has been restricted. Photodissociation is the breakup of molecules caused by exposure to photons. ... For other uses, see CFC (disambiguation). ... Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... For other uses, see Ozone (disambiguation). ... In chemistry and biology, catalysis (in Greek meaning to annul) is the acceleration of the rate of a chemical reaction by means of a substance, called a catalyst, that is itself unchanged chemically by the overall reaction. ... A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions. ... The ozone layer is a layer in Earths atmosphere which contains relatively high concentrations of ozone (O3). ... A refrigerant is a compound used in a heat cycle that undergoes a phase change from a gas to a liquid and back. ...

Free radicals in biology

Free radicals play an important role in a number of biological processes, some of which are necessary for life, such as the intracellular killing of bacteria by neutrophil granulocytes. Free radicals have also been implicated in certain cell signalling processes ^[2]. The two most important oxygen-centered free radicals are superoxide and hydroxyl radical. They are derived from molecular oxygen under reducing conditions. However, because of their reactivity, these same free radicals can participate in unwanted side reactions resulting in cell damage. Many forms of cancer are thought to be the result of reactions between free radicals and DNA, resulting in mutations that can adversely affect the cell cycle and potentially lead to malignancy. Some of the symptoms of aging such as atherosclerosis are also attributed to free-radical induced oxidation of many of the chemicals making up the body. In addition free radicals contribute to alcohol-induced liver damage, perhaps more than alcohol itself. Radicals in cigarette smoke have been implicated in inactivation of alpha 1-antitrypsin in the lung. This process promotes the development of emphysema. This article does not cite any references or sources. ... In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes and linked through second messengers resulting in what is thought of as... Lewis electron configuration of superoxide. ... Hydroxide is a functional group consisting of oxygen and hydrogen: -O−H It has a charge of 1-. The term hydroxyl group is used when the functional group -OH is counted as a substituent of an organic compound. ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... For linguistic mutation, see Apophony. ... The cell cycle, or cell-division cycle, is the series of events that take place in a eukaryotic cell leading to its replication. ... In biology, senescence is the combination of processes of deterioration which follow the period of development of an organism. ... This article does not cite any references or sources. ... For the bird, see Liver bird. ... Unlit filtered cigarettes. ... This article does not cite any references or sources. ... RNA expression pattern Orthologs Human Mouse Entrez Ensembl Uniprot Refseq Location Pubmed search alpha 1-Antitrypsin or α1-antitrypsin (A1AT) is a glycoprotein and generally known as serum trypsin inhibitor. ... Human respiratory system The lungs flank the heart and great vessels in the chest cavity. ...

Free radicals may also be involved in Parkinson's disease, senile and drug-induced deafness, schizophrenia, and Alzheimer's. The classic free-radical syndrome, the iron-storage disease hemochromatosis, is typically-associated with a constellation of free-radical-related symptoms including movement disorder, psychosis, skin pigmentary melanin abnormalities, deafness, arthritis, and diabetes mellitus. The free radical theory of aging proposes that free radicals underlie the aging process itself, whereas the process of mitohomesis suggests that repeated exposure to free radicals may extend life span. Alzheimers disease (AD) or senile dementia of Alzheimers type is a neurodegenerative disease which results in a loss of mental functions due to the deterioration of brain tissue. ... Haemochromatosis, also spelled hemochromatosis, is a hereditary disease characterized by improper processing by the body of dietary iron which causes iron to accumulate in a number of body tissues, eventually causing organ dysfunction. ... Broadly, melanin is any of the polyacetylene, polyaniline, and polypyrrole blacks and browns or their mixed copolymers. ... The free-radical theory of aging (FRTA) is that organisms age because protein, lipid and nucleic acids (DNA, RNA) accumulate free radical damage with the passage of time. ... In biology, senescence is the combination of processes of deterioration which follow the period of development of an organism. ... A very low dose of a chemical agent may trigger from an organism the opposite response to a very high dose. ... Life span is one of the most important parameters of any living organism. ...

Because free radicals are necessary for life, the body has a number of mechanisms to minimize free radical induced damage and to repair damage which does occur, such as the enzymes superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase. In addition, antioxidants play a key role in these defense mechanisms. These are often the three vitamins, vitamin A, vitamin C and vitamin E and polyphenol antioxidants. Further, there is good evidence bilirubin and uric acid can act as antioxidants to help neutralize certain free radicals. Bilirubin comes from the breakdown of red blood cells' contents, while uric acid is a breakdown product of purines. Too much bilirubin, though, can lead to jaundice, which could eventually damage the central nervous system, while too much uric acid causes gout ^[3]. Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Structure of the monomeric unit of human superoxide dismutase 2 The enzyme superoxide dismutase (SOD, EC 1. ... Catalase (human erythrocyte catalase: PDB 1DGF, EC 1. ... Glutathione peroxidase (PDB 1GP1, EC 1. ... Glutathione reductase reduces oxidized glutathione Categories: ‪Science stubs‬ | ‪Enzyme stubs‬ | ‪Biochemistry stubs‬ | ‪Biochemistry‬ ... Space-filling model of the antioxidant metabolite glutathione. ... The structure of retinol, the most common dietary form of vitamin A Vitamin A is an essential human nutrient. ... This article is about the nutrient. ... Tocopherol, or Vitamin E, is a fat-soluble vitamin in eight forms that is an important antioxidant. ... Molecular structure of flavone, a common Polyphenol antioxidant Polyphenol antioxidant is a class of multi-phenolic compounds known for their role of down-regulating free radical formation in mammals . ... Bilirubin is a yellow breakdown product of normal heme catabolism. ... Uric acid (or urate) is an organic compound of carbon, nitrogen, oxygen and hydrogen with the formula C5H4N4O3. ... “Red cell” redirects here. ... Purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. ... Look up jaundice in Wiktionary, the free dictionary. ...

Reactive oxygen species

Main article: Reactive oxygen species

Reactive oxygen species or ROS are species such as superoxide, hydrogen peroxide, and hydroxyl radical and are associated with cell damage. ROSs form as a natural byproduct of the normal metabolism of oxygen and have important roles in cell signaling. Reactive oxygen species (ROS) include oxygen ions, free radicals and peroxides both inorganic and organic. ... Reactive oxygen species (ROS) include oxygen ions, free radicals and peroxides both inorganic and organic. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ...

Loose definition of radicals

In most fields of chemistry, the historical definition of radicals contends that the molecules have nonzero spin. However in fields including spectroscopy, chemical reaction, and astrochemistry, the definition is slightly different. Gerhard Herzberg, who won the Nobel prize for his research of electronic structure and geometry of radicals, suggested a looser definition of free radicals: "any transient (chemically unstable) species (atom, molecule, or ion)"^[4]. The main point of his suggestion is that there are many chemically unstable molecules which have zero spin, such as C₂, C₃, CH₂ and so on. This definition is more convenient for discussions of transient chemical processes and astrochemistry; therefore researchers in these fields prefer to use this loose definition.^[5] Animation of the dispersion of light as it travels through a triangular prism. ... For other uses, see Chemical reaction (disambiguation). ... Astrochemistry is the study of the chemicals found in outer space, usually in molecular gas clouds, and their formation, interaction and destruction. ... Gerhard Herzberg (December 25, 1904 – March 3, 1999) was a pioneering theoretical chemist. ...

Diagnostics

Free Radical diagnostic techniques include:

• Electron Spin Resonance

A widely-used technique for studying free radicals, and other paramagnetic species, is electron spin resonance spectroscopy (ESR). This is alternately referred to as "electron paramagnetic resonance" (EPR) spectroscopy. It is conceptually related to nuclear magnetic resonance, though electrons resonate with higher-frequency fields at a given fixed magnetic field than do most nuclei.

• Nuclear magnetic resonance using a phenomenon called CIDNP
• Chemical Labelling

Chemical labelling by quenching with free radicals, e.g. with NO or DPPH, followed by spectroscopic methods like X-ray photoelectron spectroscopy (XPS) or absorption spectroscopy, respectively.

• Use of free radical markers

Stable, specific or non-specific derivates of physiological substances can be measured e.g. lipid peroxidation products (isoprostanes, TBARS), amino acid oxidation products (meta-tyrosine, ortho-tyrosine, hydroxy-Leu, dityrosine etc.), peptide oxidation products (oxidized glutathione - GSSG)

• Indirect method

Measurement of the decrease in the amount of antioxidants (e.g. TAS, reduced glutathione - GSH)

chumbawumba Electron Paramagnetic Resonance (EPR) or Electron Spin Resonance (ESR) is a spectroscopic technique which detects species that have unpaired electrons, generally meaning that the molecule in question is a free radical if it is an organic molecule, or that it has transition metal ions if it is an inorganic complex. ... Animation of the dispersion of light as it travels through a triangular prism. ... Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy is a technique for studying chemical species that have one or more unpaired electrons, such as organic and inorganic free radicals or inorganic complexes possessing a transition metal ion. ... NMR redirects here. ... Magnetic field lines shown by iron filings Magnetostatics Electrodynamics Electrical Network Tensors in Relativity This box:      In physics, the magnetic field is a field that permeates space and which exerts a magnetic force on moving electric charges and magnetic dipoles. ... NMR redirects here. ... CIDNP (Chemically Induced Dynamic Nuclear Polarization) is a non-Boltzmann nuclear spin state distribution produced in thermal or photochemical reactions, usually from colligation and diffusion, or disproportionation of radical pairs, and detected by nuclear magnetic resonance spectroscopy as enhanced absorption or emission signals. ... R-phrases , , , , S-phrases , , , Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Nitric oxide or Nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of... Basic components of a monochromatic XPS system. ... Absorption spectroscopy refers to a wide range of techniques where one measures how much light of a particular wavelength (color) is absorbed by a sample. ... Thiobarbiturate reactive substances (TBARS) are the low-molecular-weight end products, whose main component is malondialdehyde, that are formed during the decomposition of lipid peroxidation products. ... This article is about the class of chemicals. ... Tyrosine (from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese[1][2]), 4-hydroxyphenylalanine, or 2-amino-3(4-hydroxyphenyl)-propanoic acid, is one of the 20 amino acids that are used by cells... Tyrosine (from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese[1][2]), 4-hydroxyphenylalanine, or 2-amino-3(4-hydroxyphenyl)-propanoic acid, is one of the 20 amino acids that are used by cells... Tyrosine (from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese[1][2]), 4-hydroxyphenylalanine, or 2-amino-3(4-hydroxyphenyl)-propanoic acid, is one of the 20 amino acids that are used by cells... Glutathione (GSH) is a tripeptide. ... Glutathione (GSH) is a tripeptide. ...

See also

• Free-radical theory
• -yl
• Reactive oxygen species
• Oxidative stress
• Mitohormesis

The free-radical theory of aging (FRTA) is that organisms age because protein, lipid and nucleic acids (DNA, RNA) accumulate free radical damage with the passage of time. ... The suffix -yl is used in organic chemistry to form names of radicals. ... Reactive oxygen species (ROS) include oxygen ions, free radicals and peroxides both inorganic and organic. ... Oxidative stress is a medical term for damage to animal or plant cells (and thereby the organs and tissues composed of those cells) caused by reactive oxygen species, which include (but are not limited to) superoxide, singlet oxygen, peroxynitrite or hydrogen peroxide. ... A very low dose of a chemical agent may trigger from an organism the opposite response to a very high dose. ...

External links

• All about Free Radicals, Antioxidants and Longevity
• Free Radicals and Human Disease
• Electron-transfer Factors in Psychosis and Dyskinesia--early review article
• Ozone exposure generates free radicals in the blood samples in vitro.
• Use of Radical Emission for Determination of Ignition Delay Times

References

1. ^ Oakley, R.T. Prog. Inorg. Chem. 1998, 36, 299; Banister, A.J., et al. Adv. Hetero. Chem. 1995, 62, 137
2. ^ Pacher, P.; Beckman, J. S.; Liaudet, L.; “Nitric Oxide and Peroxynitrite: in Health and disease” Physiological Reviews 2007, volume 87(1), page 315-424. PMID 17237348
3. ^ An overview of the role of free radicals in biology and of the use of electron spin resonance in their detection may be found in a recent book: *Rhodes C.J.: Toxicology of the Human Environment - the critical role of free radicals, Taylor and Francis, London (2000).
4. ^ G. Herzberg (1971), "The spectra and structures of simple free radicals" ISBN 048665821X
5. ^ 28th International Symposium on Free Radicals[1]