蛋殼比金屬還要堅(jiān)硬小雞如何破殼而出英語(yǔ)美文
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.
科學(xué)家說(shuō)他們以前所未有的程度對(duì)蛋殼的結(jié)構(gòu)進(jìn)行放大并進(jìn)一步了解，揭示了它們?nèi)绾胃淖円栽试S幼雞孵化。
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.
雞蛋離開母體時(shí)蛋殼富含鈣質(zhì)，蛋殼有3層構(gòu)造，小雞在蛋殼中一點(diǎn)點(diǎn)成長(zhǎng)起來(lái)，在這個(gè)過(guò)程中，蛋殼由內(nèi)到外變薄，來(lái)自蛋殼的鈣質(zhì)也會(huì)被小雞的骨骼吸收。但在分子尺度上這一過(guò)程至今還是秘密，到底是怎么發(fā)生的呢?
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.
現(xiàn)在科學(xué)家們說(shuō)他們已經(jīng)發(fā)現(xiàn)蛋殼具有納米結(jié)構(gòu)，并且它似乎在貝殼強(qiáng)度方面起著關(guān)鍵作用。
“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.”
“每個(gè)人都認(rèn)為蛋殼很脆弱，當(dāng)我們小心翼翼，我們走在蛋殼上時(shí)，但事實(shí)上，由于它們的纖薄，它們比一些金屬更堅(jiān)硬，更硬，”該研究的合著者來(lái)自加拿大麥吉爾大學(xué)馬克麥基教授說(shuō)。 “我們正在了解蛋殼的組裝方式和分解過(guò)程。”
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.
McKee及其同事在“科學(xué)進(jìn)展”雜志上撰文，并描述他們?nèi)绾瓮ㄟ^(guò)關(guān)注骨橋蛋白這一蛋白質(zhì)的作用來(lái)探討這個(gè)問(wèn)題。這種物質(zhì)在整個(gè)蛋殼中均可發(fā)現(xiàn)，并已被認(rèn)為是組織其礦物結(jié)構(gòu)的重要組成部分。
“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.”
“像蛋殼，牙齒和骨頭那樣不同的東西，它們都含有這種蛋白質(zhì)，”麥基說(shuō)。“我們認(rèn)為這些蛋白質(zhì)能夠輔助礦化過(guò)程，并賦予這些組織特性�！�
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.
通過(guò)采用許多顯微鏡技術(shù)，以及稱為聚焦離子束的尖端方法來(lái)制備蛋殼薄片，該團(tuán)隊(duì)發(fā)現(xiàn)所有層都是由一系列小區(qū)域的結(jié)晶含鈣礦物構(gòu)成。
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.
研究小組還發(fā)現(xiàn)，外層的面積更小，排列更緊密，納米結(jié)構(gòu)朝內(nèi)層方向變大。同時(shí)發(fā)現(xiàn)骨橋蛋白含量水平在最內(nèi)層的蛋殼層中最低。
“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.
“第三個(gè)發(fā)現(xiàn)是，外殼的外部更硬，因?yàn)樗哂凶钚〉募{米結(jié)構(gòu)，然后你向內(nèi)移動(dòng)，它就會(huì)變得更柔軟一點(diǎn)，”麥基說(shuō)。
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.
該團(tuán)隊(duì)說(shuō)，骨橋蛋白似乎形成一種指導(dǎo)含鈣礦物排列的支架，從而產(chǎn)生影響蛋殼層硬度的納米結(jié)構(gòu)。
McKee says the theory is backed up by experiments in the lab.
麥基說(shuō)這個(gè)理論是由實(shí)驗(yàn)室試驗(yàn)支持的。
“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.
“如果你不把蛋白質(zhì)放進(jìn)試管里，你會(huì)得到一個(gè)巨大的方解石(碳酸鈣)晶體，就像你在博物館里找到的那樣。如果你投入蛋白質(zhì)，它減緩了整個(gè)過(guò)程，它嵌入到晶體內(nèi)部，它在這些合成晶體中產(chǎn)生非常類似的納米結(jié)構(gòu)性質(zhì)，并且提高硬度，“McKee說(shuō)。較高濃度的骨橋蛋白能夠產(chǎn)生較小的納米結(jié)構(gòu)。
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.
然后團(tuán)隊(duì)從早餐桌上的雞蛋轉(zhuǎn)向查看已經(jīng)受精并孵育15天的.雞蛋的結(jié)構(gòu)。雖然三個(gè)蛋殼層最外層的納米結(jié)構(gòu)保持不變，但內(nèi)層的納米結(jié)構(gòu)尺寸變的更小。McKee說(shuō)，這是碳酸鈣在酸性條件下溶解并用于小雞骨骼成長(zhǎng)的結(jié)果，并且該過(guò)程可能為納米結(jié)構(gòu)提高含鈣礦物表面積提供幫助。
The upshot is that the shell weakens, allowing it to crack and the chick to hatch.
這樣的結(jié)果是殼被削弱了，使得小雞孵化，蛋殼破裂成為可能。
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.
雖然其他蛋白質(zhì)在蛋殼層結(jié)構(gòu)中的作用尚未被揭露，但McKee說(shuō)最新的發(fā)現(xiàn)可能在新型人造材料的設(shè)計(jì)中具有指導(dǎo)作用。
“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.
“當(dāng)你思考這個(gè)問(wèn)題時(shí)，我們應(yīng)該尋求來(lái)自于大自然和生物學(xué)的材料，從中獲取設(shè)計(jì)材料的靈感，因?yàn)檫@些經(jīng)歷了數(shù)億年的進(jìn)化是東西可以說(shuō)是近乎完美的”他說(shuō)。
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