Medical research

Study finds direct oxidative stress damage shortens telomeres

The same sources thought to inflict oxidative stress on cells—pollution, diesel exhaust, smoking and obesity—also are associated with shorter telomeres, the protective tips on the ends of the chromosomal shoelace.

Medical research

Novel nanoparticle enhances radiation tumor killing

Radiation kills tumors by creating oxygen free radicals that damage the tumor DNA. However, the lack of oxygen in the center of tumors blocks the production of free radicals, inhibiting radiation killing. NIBIB researchers ...

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Radical (chemistry)

In chemistry, radicals (often referred to as free radicals) are atoms, molecules, or ions 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, although a radical may be trapped within a solvent cage or be otherwise bound. The first organic free radical identified was triphenylmethyl radical, by Moses Gomberg in 1900 at the University of Michigan.

Historically, the term radical has also been used for bound parts of the molecule, especially when they remain unchanged in reactions. These are now called functional groups. For example, methyl alcohol was described as consisting of a methyl "radical" and a hydroxyl "radical". Neither are radicals in the modern chemical sense, as they are permanently bound to each other, and have no unpaired, reactive electrons. They can, however, be observed as radicals in mass spectrometry after breaking down the substance with a hail of energetic electrons.

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