Selenium
描述
Selenium is a nonmetal element with the atomic number 34 and the chemical symbol Se. Isolated selenium occurs in several different forms, the most stable of which is a dense purplish-gray semiconductor form. Selenium rarely occurs in its elemental state in nature and is usually found in sulfide ores such as pyrite, partially replacing the sulfur in the ore matrix. It may also be found in silver, copper, lead, and nickel minerals. Selenium is mainly used in the electronics industry, in glassmaking, and in chemicals and pigments. Though selenium salts are toxic in large amounts, trace amounts of the element are necessary for cellular function in most animals, forming the active center of the enzymes glutathione peroxidase, thioredoxin reductase, and three known deiodinase enzymes. (L620)
类别
"Pesticide", "Household Toxin", "Industrial/Workplace Toxin", "Pollutant", "Airborne Pollutant", "Food Toxin", "Natural Toxin"
同义词
"Se(2-)", "Selanediide", "Selenide", "Selenide(2-)", "Selenium anion (2-)", "Selenium ion (Se2-)"
InChI 标识符
InChI=1S/Se/q+2
键
InChIKey=MFSBVGSNNPNWMD-UHFFFAOYSA-N
化合物类型
Inorganic compounds
大分类
Homogeneous non-metal compounds
类型
Homogeneous other non-metal compounds
直接大类
Homogeneous other non-metal compounds
取代基
"Homogeneous other non metal"
外部描述符
"monoatomic dication", "selenium ion"
地位
Detected and Not Quantified
蜂窝位置
"Cytoplasm", "Extracellular"
组织位置
"Brain", "Erythrocyte", "Hair", "Kidney", "Liver", "Muscle", "Placenta"
外貌
Gray to black crystals.
熔点/沸点/溶解度
221°C/684.9°C (1264.8°F)/
暴露途径
Oral(L619) ; inhalation (L619) ; dermal (L619).
毒性机制
Selenium readily substitutes for sulfur in biomolecules and in many biochemical reactions, especially when the concentration of selenium is high and the concentration of sulfur is low. Inactivation of the sulfhydryl enzymes necessary for oxidative reactions in cellular respiration, through effects on mitochondrial and microsomal electron transport, might contribute to acute selenium toxicity. Selenomethionine (a common organic selenium compound) also appears to randomly substitute for methionine in protein synthesis. This substitution may affect the structure and functionability of the protein, for example, by altering disulfide bridges. Inorganic forms of selenium appear to react with tissue thiols by redox catalysis, resulting in formation of reactive oxygen species and causing damage by oxidative stress. (L619)
代谢
Selenium may be absorbed through inhalation and ingestion, while some selenium compounds may also be absorbed dermally. Once in the body, selenium is distributed mainly to the liver and kidney. Selenium is an essential micronutrient and is a component of glutathione peroxidase, iodothyronine 5'-deiodinases, and thioredoxin reductase. Organic selenium is first metabolized into inorganic selenium. Inorganic selenium is reduced stepwise to the intermediate hydrogen selenide, which is either incorporated into selenoproteins after being transformed to selenophosphate and selenocysteinyl tRNA or excreted into the urine after being transformed into methylated metabolites of selenide. Elemental selenium is also methylated before excretion. Selenium is primarily eliminated in the urine and feces, but certain selenium compounds may also be exhaled. (L619)
毒性值
LD50: 6700 mg/kg (Oral, Rat) (T14)
致癌性
3, not classifiable as to its carcinogenicity to humans. (L135)
用途/来源
Most processed selenium is used in the electronics industry, but it is also used as a nutritional supplement, in the glass industry, in the preparation of pharmaceuticals, as a nutritional feed additive for poultry and livestock, in pesticide formulations, in rubber production, as an ingredient in antidandruff shampoos, and as a constituent of fungicides. It may also be found in pigments in plastics, paints, enamels, inks, and rubber. (L619)
最低风险等级
Chronic Oral: 0.005 mg/kg/day (L134)
健康影响
Chronic oral exposure to high concentrations of selenium compounds can produce a disease called selenosis. The major signs of selenosis are hair loss, nail brittleness, and neurological abnormalities (such as numbness and other odd sensations in the extremities). Animal studies have shown that selenium may also affect sperm production and the female reproductive cycle. (L619)
症状
Short-term oral exposure to high concentrations of selenium may cause nausea, vomiting, and diarrhea. Brief exposures to high levels of elemental selenium or selenium dioxide in air can result in respiratory tract irritation, bronchitis, difficulty breathing, and stomach pains. Longer-term exposure to either of these air-borne forms can cause respiratory irritation, bronchial spasms, and coughing. (L619)
维基百科链接
http://en.wikipedia.org/wiki/Selenium
创建于
2009-03-06 18:58:10 UTC
更新于
2014-12-24 20:21:13 UTC