文章来源:未知 文章作者:meng 发布时间:2010-12-03 03:27 字体: [ ]  进入论坛

There has been controversy1 about whether life originated in a hot or cold environment, and about whether enough time has elapsed(消逝) for life to have evolved to its present complexity2. But new research at the University of North Carolina at Chapel3 Hill investigating the effect of temperature on extremely slow chemical reactions suggests that the time required for evolution on a warm earth is shorter than critics might expect.

The findings are published in the Dec. 1, 2010, online early edition of the Proceedings4 of the National Academy of Sciences.

Enzymes6, proteins that jump-start chemical reactions, are essential to life within cells of the human body and throughout nature. These molecules7 have gradually evolved to become more sophisticated and specific, said lead investigator8 Richard Wolfenden, PhD, Alumni Distinguished9 Professor of biochemistry and biophysics at UNC School of Medicine.

To appreciate how powerful modern enzymes are, and the process of how they evolved, scientists need to know how quickly reactions occur in their absence.

Wolfenden's group measured the speed of chemical reactions, estimating that some of them take more than 2 billion years without an enzyme5.

In the process of measuring slow reaction rates, "it gradually dawned on(被理解,明朗化) us that the slowest reactions are also the most temperature-dependent," Wolfenden said.

In general, the amount of influence temperature has on reaction speeds varies drastically(彻底地,激烈地) , the group found. In one slow reaction, for instance, raising the temperature from 25 to 100 degrees Celsius10 increases the rate 10 million fold. "That is a shocker," Wolfenden said. "That's what's going to surprise people most, as it did me."

That is surprising, Wolfenden said, because a textbook rule in chemistry — for more than a century —has been that the influence of temperature is modest. In particular, a doubling in reaction rate occurs when the temperature rises 10 degree Celsius, according to experiments done in 1866.

High temperatures were probably a crucial influence on reaction rates when life began forming in hot springs and submarine vents11(通风管) , Wolfenden said. Later, the cooling of the earth provided selective pressure for primitive12 enzymes to evolve and become more sophisticated, the Wolfenden's group hypothesizes.

Using two different reaction catalysts13 — which are not protein enzymes but that may have resembled early precursors14 to enzymes — the group put the hypothesis to the test. The catalyzed15 reactions are indeed far less sensitive to temperature, compared with reactions that are accelerated by catalysts. The results are consistent with our hypothesis(假设) , Wolfenden said.

Wolfenden's group plans to test the hypothesis using other catalysts. In the meantime, these findings are likely to influence how scientists think of the first primitive(原始的,远古的) forms of life on earth, and may affect how researchers design and enhance the power of artificial catalysts, he added.


1 controversy 6Z9y0     
  • That is a fact beyond controversy.那是一个无可争论的事实。
  • We ran the risk of becoming the butt of every controversy.我们要冒使自己在所有的纷争中都成为众矢之的的风险。
2 complexity KO9z3     
  • Only now did he understand the full complexity of the problem.直到现在他才明白这一问题的全部复杂性。
  • The complexity of the road map puzzled me.错综复杂的公路图把我搞糊涂了。
3 chapel UXNzg     
  • The nimble hero,skipped into a chapel that stood near.敏捷的英雄跳进近旁的一座小教堂里。
  • She was on the peak that Sunday afternoon when she played in chapel.那个星期天的下午,她在小教堂的演出,可以说是登峰造极。
4 proceedings Wk2zvX     
  • He was released on bail pending committal proceedings. 他交保获释正在候审。
  • to initiate legal proceedings against sb 对某人提起诉讼
5 enzyme cPozF     
  • Above a certain temperature,the enzyme molecule will become unfolded.超过一定温度,酶分子将会展开。
  • An enzyme that dissolves the fibrin of blood clots.能溶解血凝块中的纤维的酶。
6 enzymes 7881ad8ce9c83424f7874e70266ed2d8     
n. 酶,酵素
  • It was said that washing powders containing enzymes remove stains more efficiently. 据说加酶洗衣粉除污更有效。
  • Among the enzymes which are particularly effective are pepsin, papain. 在酶当中特别有效的是胃朊酶、木瓜酶。
7 molecules 187c25e49d45ad10b2f266c1fa7a8d49     
分子( molecule的名词复数 )
  • 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。
8 investigator zRQzo     
  • He was a special investigator for the FBI.他是联邦调查局的特别调查员。
  • The investigator was able to deduce the crime and find the criminal.调查者能够推出犯罪过程并锁定罪犯。
9 distinguished wu9z3v     
  • Elephants are distinguished from other animals by their long noses.大象以其长长的鼻子显示出与其他动物的不同。
  • A banquet was given in honor of the distinguished guests.宴会是为了向贵宾们致敬而举行的。
10 Celsius AXRzl     
  • The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
  • The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。
11 vents 3fd48768f3da3e458d6b73926735d618     
(气体、液体等进出的)孔、口( vent的名词复数 ); (鸟、鱼、爬行动物或小哺乳动物的)肛门; 大衣等的)衩口; 开衩
  • He always vents his anger on the dog. 他总是拿狗出气。
  • The Dandelion Patch is the least developed of the four active vents. “蒲公英区”在这四个活裂口中是发育最差的一个。
12 primitive vSwz0     
  • It is a primitive instinct to flee a place of danger.逃离危险的地方是一种原始本能。
  • His book describes the march of the civilization of a primitive society.他的著作描述了一个原始社会的开化过程。
13 catalysts 677fdea123458fc2ff92eb84d07254e9     
n.催化剂( catalyst的名词复数 );触媒;促进因素;有感染力的人
  • The first catalytic converters were called conventional oxidation catalysts. 最初的转化器叫做常规氧化催化器。 来自辞典例句
  • Many processes that are essential to the chemical industry use heterogeneous catalysts. 很多重要的化学工业过程就是使用多相催化剂的。 来自辞典例句
14 precursors 5e19fce64ab14f5a4b5c8687640c2593     
n.先驱( precursor的名词复数 );先行者;先兆;初期形式
  • Phenyl (or polyphenyl) substituted epoxides serve as excellent precursors to phenyl (or diphenyl) carbenes. 某些苯代(或多苯)环氧乙烷是制取带苯环(或二苯)碳烯的极好原料。 来自辞典例句
  • Note the presence of megakaryocytes, erythroid islands, and granulocytic precursors. 可见巨核细胞,红细胞岛和粒细胞前体细胞。 来自互联网
15 catalyzed 064244d5918af26ff76d42aea2003d91     
v.催化,促进( catalyze的过去式和过去分词 )
  • Modern technology catalyzed tremendous economic growth in China. 现代技术促成了中国经济的巨大发展。 来自辞典例句
  • The mechanisms of sorption-catalyzed organophosphate hydrolysis are not well understood. 吸附催化水解有机磷的机制还不太清楚。 来自辞典例句
TAG标签: time life research