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英语科学小知识:小鸡的破壳而出双语阅读

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这是一个很难破解的问题,但科学家们说,他们已经将蛋壳周围的结构放大到了前所未有的程度,揭示了它们是如何改变以允许幼鸟孵化的。
 
在产卵前,鸟蛋形成一个坚硬的富钙外壳,有三层。虽然已经知道,这些最薄的从一只小鸡出来的最细的东西在为孵化做准备——在这个过程中,壳中的钙被加入到它的骨架中——在分子尺度上发生的事情是一件神秘的事。
 
现在科学家们说他们已经发现,蛋壳有纳米结构,而且它似乎在外壳的强度起着关键的作用。
 
“大家都认为蛋壳是脆弱的–[时]我们小心翼翼,我们走在蛋壳–但事实上,他们的薄他们非常强大,比金属更难,”Prof Marc McKee说,在加拿大的合著者,来自麦克吉尔大学的研究。“我们现在真的很了解蛋壳是如何组装的,以及它是如何溶解的。”
 
在科学杂志上的进步写作,McKee和他的同事们描述了他们如何探索问题围绕蛋白骨桥蛋白的作用。这种物质在蛋壳中被发现,并被认为在组织矿物结构中起着重要作用。
 
“作为不同的东西作为一个蛋壳和牙齿和骨头,他们都有这种蛋白质,”McKee说。“我们认为这是蛋白一样,帮助指导矿化过程给这些组织的性质。”
 
研究小组利用大量的显微镜技术,以及一种尖端的离子束制备蛋壳薄片的方法,发现所有这些层似乎都是由含有含钙晶体矿物的微小区域形成的。
 
研究小组还发现,这些区域更小,更紧密地排列在外层,纳米结构向着内层变大。在最内层蛋壳层中骨桥蛋白的含量最低。
 
“第三发现外面的壳是因为它具有最小的[结构]然后你向内移动,它变得柔软的努力,”McKee说。
 
研究小组说,结果是骨桥蛋白似乎形成了一种支架来引导含钙矿物的排列,产生一种影响蛋壳层硬度的纳米结构。
 
McKee说,这个理论是由实验室实验
 
如果你不把试管里的蛋白质放进去,你就会在博物馆里看到一块巨大的巨大方解石(碳酸钙)晶体。如果你把蛋白质,它减慢过程下来,它被嵌入水晶,它产生一个非常相似的结构特性的人工晶体,他们增加了硬度,”McKee说。高浓度的骨桥蛋白被发现产生更小的纳米结构。
 
然后转身从鸡蛋,风在我们的早餐桌上看着鸡蛋结构已受精和孵化了15天。虽然三层蛋壳层最外层的纳米结构保持不变,但内部的纳米结构尺寸却变小了。,McKee说,是由于碳酸钙溶解在酸性条件下,用鸡的骨架,和过程可能是辅助的纳米结构增加表面面积的含钙矿物。
 
结果是外壳变弱,使它破裂,小鸡孵化。
 
而在蛋壳层结构蛋白的作用还没有被拆开,McKee说,新的发现可以在新的人造材料的设计被证明是有用的。
 
他说:“当你想到这一点的时候,我们应该做的是受自然和生物学启发的材料,因为,孩子们,在完善某件事情上,真的很难打破亿万年的进化。”。

It’s been a tough one to crack, but scientists say they have zoomed in, to an unprecedented degree, on the structure of shells surrounding chicken embryos, revealing how they change to allow young birds to hatch.

Before being laid, bird eggs form a hard calcium-rich shell with three main layers. While it was already known that these thin from the innermost out as a chick grows in preparation for hatching – with calcium from the shell being incorporated into its skeleton in the process – quite what happens at the molecular scale has been something of a mystery.

Now scientists say they have discovered that eggshells have a nanostructure, and that it appears to play a key role in the strength of the shell.

“Everybody thinks eggshells are fragile – [when] we’re careful, we ‘walk on eggshells’ – but in fact, for their thinness they are extremely strong, harder than some metals,” said Prof Marc McKee, a coauthor of the study from McGill University in Canada. “We are really understanding now at the almost molecular scale how an eggshell is assembled and how it dissolves.”

Writing in the journal Science Advances, McKee and colleagues describe how they probed the issue by focusing on the role of a protein known as osteopontin. This substance is found throughout the eggshell and was already thought to be important in organising the structure of its minerals.

“Something as different as an eggshell and a tooth and a bone, they all have this protein,” said McKee. “We think it is proteins like that that help guide the mineralisation process to give these tissues their properties.”

Using a number of microscopy techniques, as well as a cutting-edge method known as focused-ion beam for preparing thin sections of the eggshell, the team found that all of the layers appear to be formed from an array of tiny areas packed with a crystalline calcium-containing mineral.

The team also found the areas are smaller and more closely arranged in the outer layer, with the nanostructure becoming larger towards the inner layers. Levels of osteopontin were found to be lowest in the innermost eggshell layer.

“The third discovery was that the outside of the shell is harder as it has the smallest [nanostructure] and then you move inwards and it gets a little bit softer,” said McKee.

The team say the upshot is that osteopontin seems to form a sort of scaffold that guides the arrangement of calcium-containing mineral, generating a nanostructure that affects the hardness of the eggshell layer.

McKee says the theory is backed up by experiments in the lab.

“If you don’t put in the protein in the test tube you get a big giant calcite [calcium carbonate] crystal like you’d find in a museum. If you throw in the protein, it slows the process down, it gets embedded inside that crystal and it generates a very similar nanostructure property in those synthetic crystals and they have increased hardness,” said McKee. Higher concentrations of osteopontin were found to produce a smaller nanostructure.

The team then turned from the eggs that wind up on our breakfast tables to looking at the structure of chicken eggs that had been fertilised and incubated for 15 days. While the nanostructure of the outermost of the three eggshell layers remained unchanged, the nanostructure of the inner layers had become smaller in size. That, said McKee, is a result of calcium carbonate being dissolved in acidic conditions and used in the chick’s skeleton, and the process might be aided by the nanostructure increasing the surface area of the calcium-containing mineral.

The upshot is that the shell weakens, allowing it to crack and the chick to hatch.

While the role of other proteins in the structure of eggshell layers has yet to be unpicked, McKee said the latest findings could prove useful in the design of new human-made materials.

“When you think about it, we should be making materials that are inspired by nature and by biology because, boy, it is really hard to beat hundreds of millions of years of evolution in perfecting something,” he said.

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