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The free radical theory of aging states that organisms age because cells accumulate free radical damage over time. [1] A free radical is any atom or molecule that has a single unpaired electron in an outer shell. [2] While a few free radicals such as melanin are not chemically reactive, most biologically relevant free radicals are highly ...
The mitochondrial theory of ageing has two varieties: free radical and non-free radical. The first is one of the variants of the free radical theory of ageing. It was formulated by J. Miquel and colleagues in 1980 [1] and was developed in the works of Linnane and coworkers (1989). [2] The second was proposed by A. N. Lobachev in 1978. [3]
Initiation: The reaction is started by a free-radical source which may be a decomposing radical initiator such as AIBN. In the example in Figure 5, the initiator decomposes to form two fragments (I•) which react with a single monomer molecule to yield a propagating (i.e. growing) polymeric radical of length 1, denoted P 1 •.
Radicals can undergo a disproportionation reaction through a radical elimination mechanism (See Fig. 1). Here a radical abstracts a hydrogen atom from another same radical to form two non-radical species: an alkane and an alkene. Radicals can also undergo an elimination reaction to generate a new radical as the leaving group.
A free-radical reaction is any chemical reaction involving free radicals. This reaction type is abundant in organic reactions . Two pioneering studies into free radical reactions have been the discovery of the triphenylmethyl radical by Moses Gomberg (1900) and the lead-mirror experiment [ 1 ] described by Friedrich Paneth in 1927.
Oxidative stress mechanisms in tissue injury. Free radical toxicity induced by xenobiotics and the subsequent detoxification by cellular enzymes (termination).. 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. [1]
Chain propagation: A radical reacts with a non-radical to produce a new radical species; Chain termination: Two radicals react with each other to create a non-radical species; In a free-radical addition, there are two chain propagation steps. In one, the adding radical attaches to a multiply-bonded precursor to give a radical with lesser bond ...
The common mechanism is a free radical chain reaction, where the addition of oxygen gives rise to hydroperoxides and their associated peroxy radicals (ROO•). [5] Typically, an induction period is seen at the start where there is little activity; this is followed by a gradually accelerating take-up of oxygen, giving an autocatalytic reaction ...