太阳光对人体的三重伤害-凯发k8官网

太阳光对人体的三重伤害
文章来源:未知 文章作者:enread 发布时间:2014-10-22 07:15 字体: [ ] 
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the most obvious effects of too much sun exposure are 1, like wrinkled and rough skin. some damage, however, goes deeper -- ultraviolet light can damage 2 and cause proteins in the body to break down into smaller, sometimes harmful pieces that may also damage dna, increasing the risk of skin cancer and 3. understanding the specific pathways by which this 4 occurs is an important step in developing protective 5 against it. researchers from the école polytechnique fédérale de lausanne (epfl) in switzerland have shown that certain peptides (small proteins) degrade under uv light by first passing through a triplet quantum state, a reactive arrangement that can cause greater damage than fragmentation alone.
 
their results, described in a paper appearing this week in the journal of chemical physics, from aip publishing, explore this pathway of protein degradation and could facilitate the development of better uv protection mechanisms.
 
the researchers took gas-phase peptides containing tyrosine or phenylalanine, light-absorbing amino acids found throughout our bodies, and subjected them to ultraviolet laser radiation. then, they used ultraviolet-infrared spectroscopy to examine the resulting 6 changes over time. they found that instead of immediately degrading once excited, some of the 8 formed intermediate triplet states.
 
normally, electron spins are paired -- if two electrons are present, one spin points one direction and the other points the opposite direction. but under certain conditions, the spin of one of the electrons can 9 so that they both point in the same direction. this arrangement is known as a triplet state.
 
because electronic 10 can affect how a 7 will react, knowing that it passes through a triplet state can provide additional insight into the potential consequences of photodamage for these molecules.
 
"triplet states are long-lived and can be involved in harmful chemical reactions," said chemical 11 aleksandra zabuga, an author of the new paper. "long-lived" is relative -- they still only last from microseconds to milliseconds -- but it does give them a greater opportunity to do damage.
 
"during that time the triplet species may transfer their energy to nearby oxygen and produce highly reactive singlet oxygen or other free 12. these radicals can in turn move around the cell and cause dna damage that is much more dangerous than the fragmentation of peptides," she said.


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1 qygz2     
n.化妆品;adj.化妆用的;装门面的;装饰性的
参考例句:
  • these changes are purely cosmetic.这些改变纯粹是装饰门面。
  • laughter is the best cosmetic,so grin and wear it!微笑是最好的化妆品,所以请尽情微笑吧!
2 4u3z1l     
(缩)deoxyribonucleic acid 脱氧核糖核酸
参考例句:
  • dna is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
  • gene mutations are alterations in the dna code.基因突变是指dna密码的改变。
3 a219fc2c9b1a7afeeb9c811d4d48060a     
n.大瀑布( cataract的名词复数 );白内障
参考例句:
  • the rotor cataracts water over the top of the machines. 回转轮将水从机器顶上注入。 来自《现代英汉综合大词典》
  • cataracts of rain flooded the streets. 倾盆大雨弄得街道淹水。 来自辞典例句
4 qxkxl     
n.降级;低落;退化;陵削;降解;衰变
参考例句:
  • there are serious problems of land degradation in some arid zones.在一些干旱地带存在严重的土地退化问题。
  • gambling is always coupled with degradation.赌博总是与堕落相联系。
5 d0db71d70348ef1c49f05f59097917b8     
n.机械( mechanism的名词复数 );机械装置;[生物学] 机制;机械作用
参考例句:
  • the research will provide direct insight into molecular mechanisms. 这项研究将使人能够直接地了解分子的机理。 来自《简明英汉词典》
  • he explained how the two mechanisms worked. 他解释这两台机械装置是如何工作的。 来自《简明英汉词典》
6 itxw5     
adj.构造的,组织的,建筑(用)的
参考例句:
  • the storm caused no structural damage.风暴没有造成建筑结构方面的破坏。
  • the north american continent is made up of three great structural entities.北美大陆是由三个构造单元组成的。
7 y6tzn     
n.分子,克分子
参考例句:
  • a molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由p妈?f婘??妈?成的。
  • this gives us the structural formula of the molecule.这种方式给出了分子的结构式。
8 187c25e49d45ad10b2f266c1fa7a8d49     
分子( molecule的名词复数 )
参考例句:
  • the structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
  • inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里,大分子裂变为小分子。
9 vjwx6     
vt.快速翻动;轻抛;轻拍;n.轻抛;adj.轻浮的
参考例句:
  • i had a quick flip through the book and it looked very interesting.我很快翻阅了一下那本书,看来似乎很有趣。
  • let's flip a coin to see who pays the bill.咱们来抛硬币决定谁付钱。
10 86f23519571eb918e8812e1979d55409     
n.[化学]结构( configuration的名词复数 );构造;(计算机的)配置;构形(原子在分子中的相对空间位置)
参考例句:
  • such configurations, obtained theoretically by calculation, are called models of a star. 通过理论计算得到的恒星结构称为恒星模型。 来自辞典例句
  • the other two configurations have overriding advantages for special applications. 其它两种接法对特殊应用具有突出的优点。 来自辞典例句
11 onqx4     
n.物理学家,研究物理学的人
参考例句:
  • he is a physicist of the first rank.他是一流的物理学家。
  • the successful physicist never puts on airs.这位卓有成就的物理学家从不摆架子。
12 5c853925d2a610c29b107b916c89076e     
n.激进分子( radical的名词复数 );根基;基本原理;[数学]根数
参考例句:
  • some militant leaders want to merge with white radicals. 一些好斗的领导人要和白人中的激进派联合。 来自《简明英汉词典》
  • the worry is that the radicals will grow more intransigent. 现在人们担忧激进分子会变得更加不妥协。 来自辞典例句
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