Selenium
hideSelenium (pronounced /səˈliːniəm/) is a chemical element with the atomic number 34, represented by the chemical symbol Se, an atomic mass of 78.96. It is a nonmetal, chemically related to sulfur and tellurium, and rarely occurs in its elemental state in nature.
Isolated selenium occurs in several different forms, the most stable of which is a dense purplish-gray semi-metal (semiconductor) form that is structurally a trigonal polymer chain. It conducts electricity better in the light than in the dark, and is used in photocells (see allotropes section below). Selenium also exists in many non-conductive forms: a black glass-like allotrope, as well as several red crystalline forms built of eight-membered ring molecules, like its lighter chemical cousin sulfur.
Selenium is found in economic quantities in sulfide ores such as pyrite, partially replacing the sulfur in the ore matrix. Minerals that are selenide or selenate compounds are also known, but all are rare. The chief commercial present uses for selenium are in glassmaking and in chemicals and pigments. Electronic uses for selenium, once important, have been supplanted by silicon semiconductor devices.
Selenium salts are toxic in large amounts, but trace amounts of the element are necessary for cellular function in most, if not all, animals, forming the active center of the enzymes glutathione peroxidase and thioredoxin reductase (which indirectly reduce certain oxidized molecules in animals and some plants) and three known deiodinase enzymes (which convert one thyroid hormone to another). Selenium requirements in plants differ by species, with some plants apparently requiring none.
For more information about Selenium, read the full article at
Wikipedia.
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News tagged with selenium
Too much selenium can increase your cholesterol
Nov 12, 2009 |
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A new study from the University of Warwick has discovered taking too much of the essential mineral selenium in your diet can increase your cholesterol by almost 10%.
Nanometric butterfly wings created
Nanotechnology / Nanomaterials
Oct 08, 2009 |
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A team of researchers from the State University of Pennsylvania (USA) and the Universidad Autónoma de Madrid (UAM) have developed a technique to replicate biological structures, such as butterfly wings, ...
Antioxidants not associated with increased melanoma risk
Aug 17, 2009 |
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Antioxidant supplements do not appear to be associated with an increased risk of melanoma, according to a report in the August issue of Archives of Dermatology.
Selenium intake may worsen prostate cancer in some, study reports
Jun 25, 2009 |
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BOSTON--Higher selenium levels in the blood may worsen prostate cancer in some men who already have the disease, according to a study by researchers at Dana-Farber Cancer Institute the University of California, San Francisco.
Prairie dogs: influencing the accumulation of metals in plants?
Jun 23, 2009 |
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Prairie dogs may seem like harmless little creatures, but they can inflict serious injury on plants simply by snacking on them. Plants cannot flee from their furry predators, so how do they avoid becoming ...
Diet may reduce risk of prostate cancer
Jun 03, 2009 |
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A new review published in the Journal of Human Nutrition and Dietetics assessed whether certain modifications in diet have a beneficial effect on the prevention of prostate cancer. Results suggest that a diet low in fat an ...
Vitamin E, selenium and soy in combination does not prevent prostate cancer
Apr 26, 2009 |
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The combination therapy of vitamin E, selenium and soy does not prevent the progression from high-grade prostatic intraepithelial neoplasia (HGPIN) to prostate cancer, according to the new research presented at the 104th ...
Study finds selenium, vitamin E do not prevent prostate cancer
Dec 09, 2008 |
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Findings from one of the largest cancer chemoprevention trials ever conducted have concluded that selenium and vitamin E taken alone or in combination for an average of five and a half years did not prevent prostate cancer, ...
Selenium may prevent high risk-bladder cancer
Dec 08, 2008 |
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A study published in the December issue of Cancer Prevention Research, a journal of the American Association for Cancer Research, suggests that selenium, a trace mineral found in grains, nuts and meats, may aid in the pr ...
Selenium may slow march of AIDS
Medicine & Health / HIV & AIDS
Nov 28, 2008 |
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Increasing the production of naturally occurring proteins that contain selenium in human blood cells slows down multiplication of the AIDS virus, according to biochemists.
Biological selenium removal: The solution to pollution?
Sep 15, 2008 |
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Selenium has been referred to as an "essential toxin" due to the fact that it shows only a marginal line between the nutritious requirement and toxic effects upon exposure. The steep dose response curve due to bioaccumulation ...
