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11/15/06--含有重复结构链的大分子多聚物被用于从轮船和输油管道的涂层以减小流动阻力到基因治疗等各个领域。

但是多聚物长链容易断裂--分解，以前许多科学家认为的多聚物分解是由于象冲向船头波浪一样强大流动力引起的，而密歇根大学的一项新研究表明这是错误的。

化学工程、大分子科学和工程学系副主任Michael Solomon说这些是重要的，因为分解了的多聚物不能象预期的一样工作，假如科学家不知道什么原因引起他们断裂，那么他们就不能令其保持不断裂，也不能设计其在特殊的环境断裂。

上周发表于国家科学院年报（PNAS，Proceedings of the National Academy of Sciences）杂志一篇文献的共同作者Solomon说，科学家们在过去的40年里没有确切地理解是什么力量导致分解。在论文Universal scaling for polymer chain scission in turbulence（湍流中多聚物链分解的普遍标准）里，他们定义了在湍流中哪种力流以及这些力处于什么水平时导致分解。

Solomon说：“该论文以一种新的方式来理解多聚物如何断裂，解决了一些存在了40年的问题。”

Solomon说，产生流行的分解理论的那些实验没有考虑到实验过程中发生于气（水）流中的湍流以及湍流如何导致断裂，那些实验只测量了层流或者匀流，而没有湍流。

然而，这个密歇根大学的研究小组发现湍流的确存在而且对多聚物的影响很大。 在会机械工程、海军建筑和潜艇工程学系的安排下，Solomon和共同作者Steven Ceccio与当时的博士生Siva Vanapalli建立和测定了不同多聚物的共式，并且确切地指出了它们对不同的气（水）流的反应，Siva Vanapalli现在是特文特大学（Twente University）的博士后研究生。

他们建立的方程可以应用于设计气（水）流来把多聚物断裂成某一长度，或者设计可以承受一定气（水）流的多聚物。这对轮船工业、石油工业等依靠多聚物涂层的工厂影响巨大。

Ceccio说：“多聚物工作的最好状态下，摩擦力可以减小70%。”

该研究对基因治疗领域也有影响，它令科学家掌握了一个控制DNA链长度的工具。在基因组测序过程中，第一步就是找到染色体组并且将其断裂成小片段，然后重组在进行进一步生化研究的DNA链上，Solomon说。

该研究由国防部资助。是检测许多种摩擦阻力大型工程的一部分，密歇根大学研究小组是在田纳西州一个海军拥有的设施William B. Morgan空化水洞中进行的这项试验。

来源：密歇根大学

简评：

它山之石，可以攻玉……
这是物理学的研究前沿吧，但是其方法确实是可以运用到医学领域，殊不知医学无时无刻都在应用着很多基础学科的知识啊，基础学科为我们的研究提供方法学上的支持，只要我们运用好了，就会取得事半功倍的效果。Scientists Find New Way to

Manipulate DNA

11/15/06 -- Polymers, large molecules comprised of chains of repeating structures, are used in everything from the coatings on walls of ships and pipes to reduce flow drag to gene therapy.

But long polymer chains are subject to breakage, called scission, and a new study by the University of Michigan shows that as it turns out, much of what scientists previously thought about why polymers break when subjected to strong flows, such as waves crashing against a ship's bow, was wrong.

This is important for a few reasons, said Michael Solomon, associate professor in the Department of Chemical Engineering, Macromolecular Science and Engineering Program. Broken polymers don't function as intended, and if scientists don't know what causes them to break, they can't keep them from breaking, nor can they design them to break in specific places.

For the past 40 years, scientists have not understood exactly which forces caused scission, said Solomon, who is the co-author on a paper published last week in the Proceedings of the National Academy of Sciences. The paper, "Universal scaling for polymer chain scission in turbulence," defines which flow forces and at what levels those forces cause polymers to break in turbulence.

"This paper understands how they are breaking in a new way that resolves some issues that have been present for 40 years," Solomon said.

The experiments that yielded the prevailing scission theories, Solomon said, did not take into account turbulence in the flow that occurred during the experiments, and how that turbulence attributed to polymers breaking. Those experiments measured only laminar or smooth flow, which is turbulent free.

Yet, during their own experiments, the U-M team discovered that flow turbulence did indeed exist and that it was impacting the polymer quite a bit. Through experiments that accounted for turbulent flow, Solomon and co-authors Steven Ceccio, with appointments in the Department of Mechanical Engineering and Naval Architecture and Marine Engineering, and then-doctoral student Siva Vanapalli, were able to develop and test formulas for different polymers, and pinpoint exactly how they would react to different flows. Vanapalli is now a post-doctoral fellow at Twente University in the Netherlands.

The equation they developed can be applied to design flows that break polymers into certain lengths, or to design polymers to withstand certain flows. This could have big implications for industries that rely on polymer coatings, such as shipping or oil.

"When the polymers are working their best the friction can be reduced by 70 percent," Ceccio said.

The research also has implications in the field of gene therapy, allowing scientists another tool to control the length of the strands of DNA. In genome sequencing, the first step is to take the genome and break it into small pieces to reassemble it into the DNA strand that is best for further biochemistry, Solomon said.

The research is supported by the Department of Defense. It's part of a larger project to examine many kinds of friction drag, and the U-M team has been conducting experiments at the William B. Morgan Large Cavitation Channel, a Navy-owned facility in Tennessee.

Source: University of Michigan

http://www.bio.com/newsfeatures/newsfeatures_research.jhtml;jsessionid=YZUXJPJ1SVJPHR3FQLMSFEWHUWBNQIV0?cid=23800002

编辑：蓝色幻想