德國科學(xué)家發(fā)現(xiàn)貝殼能產(chǎn)生新型膠狀物

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據(jù)每日科學(xué)網(wǎng)報(bào)道，全世界的化學(xué)家們也許可以從某些貝類獲得新的知識(shí)。科學(xué)家近日發(fā)現(xiàn)，貝殼能產(chǎn)生一種能緊緊粘在金屬和石頭上的粘附劑，即使在水中也是如此，而且膠狀物的粘度都非常強(qiáng)。這些貝類就像兒童玩具一樣，產(chǎn)生的聚合物不僅不會(huì)造成自然界的二次污染，而且無毒，最有意思的是這種新型膠狀物的產(chǎn)生過程也很有戲劇性。

據(jù)報(bào)道，這種新型膠狀物是由德國馬普聚合物研究院和德國美因茨大學(xué)的研究員共同發(fā)現(xiàn)。德國科學(xué)家表示，在不久的將來，人類也許可以利用貝類產(chǎn)生的90%的這種膠狀聚合物，如此一來，就可以通過不使用任何其他化學(xué)粘合劑就能把物體粘到其他的金屬和石頭表面，就像兒童玩具一樣可以“搭更多的積木”。

科學(xué)家發(fā)現(xiàn)，貝類生命力很強(qiáng)，最有意思的是這種新型膠狀物的產(chǎn)生過程也很有戲劇性。當(dāng)它們定居在海岸附近的海底時(shí)，海浪會(huì)來回地沖擊它們。為了不被波浪沖走，這些貝類就使用特殊蛋白質(zhì)來將自己緊緊地粘在其他物體上。在分泌的過程中，這些特殊的蛋白質(zhì)就形成了這種新型膠狀聚合物。它們的產(chǎn)生是伴隨著貝殼的斗爭。對(duì)于貝殼的這一點(diǎn)，即使是最優(yōu)秀的工程師也很難達(dá)辦到這一點(diǎn)——抵御水的沖擊，形成水中的附著力。

與美因茨馬普聚合物研究院主任漢斯-巴特和美因茲大學(xué)伍爾夫?qū)?崔梅爾教授共同研究的科學(xué)家們現(xiàn)在已經(jīng)能夠人工合成粘性貝類蛋白質(zhì)聚合物。據(jù)介紹，這些聚合物包括分子長鏈和制造貝類蛋白質(zhì)膠粘劑的化學(xué)劑。美因茲的研究員還發(fā)現(xiàn)，除非能攜帶粘合多巴的化學(xué)鏈中的鍵數(shù)量少于總數(shù)的10%，鍵數(shù)量與化學(xué)鏈的粘性完全沒有關(guān)系。有了氨基酸二羥苯丙氨酸（別名：多巴），這些貝類就能緊緊地粘在水底的其他物體上。它的化學(xué)結(jié)構(gòu)使其能與金屬和礦物穩(wěn)定地結(jié)合，并且它所包含的粘合蛋白質(zhì)使它緊緊地粘在海底。

美因茨馬普聚合物研究院主任漢斯-巴特說：“事實(shí)上，粘合作用在一定程度上與粘合劑的數(shù)量并沒有多大的關(guān)系。”舉例來說，化學(xué)家能制造一種聚合物來把它均勻地粘在各種物體上。多巴能與金屬和礦物緊密的粘在一起?；瘜W(xué)家能制造出其他帶有該聚合體鏈的粘合劑來黏合木材，玻璃或骨骼。

現(xiàn)在科學(xué)家已經(jīng)通過實(shí)驗(yàn)找出來一個(gè)方法。他們把一層該聚合物鋪在鈦表面。把這個(gè)鈦尖端放到原子顯微鏡下，他們就能看到該聚合物的一條鏈，就像一個(gè)人能用手指把螺絲從桌子上撿起來。然后他們把鈦尖端從邊面分離，并且測量所需的力度。將鈦表面和聚合物的多巴分離開所需的力度為67皮牛頓。這中聚合物本身就像一個(gè)松彈簧，在下一個(gè)連接點(diǎn)斷開之前力度幾乎保持不變?，F(xiàn)在，這些研究員想要把這個(gè)實(shí)驗(yàn)的發(fā)現(xiàn)運(yùn)用到生產(chǎn)粘合各種物質(zhì)的聚合物。這樣，我們的日常生活將會(huì)發(fā)生巨大的變化。


Shellfish Inspire New AdhesivesScienceDaily (Nov. 21, 2008) — Chemists can learn from some shellfish. Mussels, for example, produce an adhesive that sticks strongly to metal and stone, even under water. Chemists have reproduced the protein responsible for this in a synthetic material that contains the same adhesive elements. Irrespective of whether the adhesive is completely made up of these elements or whether they represent just a tenth of its make-up, adhesion is equally good.
These findings were made by researchers at the Max Planck Institute for Polymer Research and at the Johannes Gutenberg University in Mainz. It might be possible to use the 90% of the polymers that are not necessary to create a good bond for other functions by providing them with chemical adjuncts which will allow them to adhere to surfaces other than metal or stone.
Some shellfish have a hard life: when they settle at the bottom of the sea close to the coast, the constant surging to and fro of the surf pulls at them. So that they are not washed away by the waves, the shellfish use special proteins to attach themselves firmly to a foundation - an ability that engineers still find difficult to achieve: adhesion under water. The shellfish can do this thanks to the amino acid dihydroxyphenylalanine, also known as dopa. Its chemical structure allows it to form very stable bonds with metals and minerals and is contained in the adhesion proteins with which shellfish attach themselves to the sea bed.
Scientists working with Hans-Jürgen Butt, Director at the Max Planck Institute for Polymer Research in Mainz, and Professor Wolfgang Tremel from the University of Mainz, have now reproduced the adhesive shellfish proteins with artificial polymers. These consist of long chains of molecules and carry the same chemical adjuncts that make the shellfish proteins adhesive. As the researchers in Mainz have now discovered, the number of the links in the chain carrying the binding dopa adjuncts has no overall relevance for the chain’s adhesiveness, provided it is not less than 10% of the total.
The researchers measured the force which allowed them to detach different polymer chains from a surface. They tested polymers that consisted completely of links with the binding dopa adjunct and some where it was only present on a fifth or a tenth of the links. The force required to pull a single polymer from the surface was always the same: 67 piconewtons. This is equivalent to a millionth of the weight force of a flea. This force alone could not keep a shellfish on the bottom of the sea. However, the creatures attach themselves firmly with a dab containing innumerable polymer chains, which allows them to brave the movement of the waves.
"The fact that the adhesive effect is, to a certain extent, independent on the number of binding sites could be used to give the other links in the polymer other functions," says Hans-Jürgen Butt. For example, chemists could manufacture a polymer that adheres equally to different materials. Dopa bonds predominantly with metals and minerals. Chemists could provide other links in the polymer chain with adjuncts that adhere to wood, glass or bone. Adhesives which bond metal and bone would be interesting for securing artificial joints," says Wolfgang Tremel.
At first, the researchers in Mainz were puzzled as to why the adhesive strength of the polymer chains was largely independent of the number of adhesive links. "Normally, we imagine that an adhesive polymer is like a strip of scotch tape that adheres over the whole of its length," says Hans-Jürgen Butt. However, the more an adhesive strip bonds to a surface, the harder it is to pull it off. This model, which describes the adhesiveness of a polymer as a continuous force, does not apply to shellfish proteins and their artificial counterparts.
"We see our polymers as chains of single binding sites linked with very loose springs," says Wolfgang Tremel. When they peel them off, he and his team measure only the force with which a single binding site is anchored to the surface. How closely the adhesive links in the chain follow each other is then irrelevant.
The density of the binding sites would have an effect if a weight was pulling evenly across the whole length of the polymer and not from one end. "In practice, this only plays a part when the surface is completely level," explains Butt. "Most surfaces are very rough at nano level, so that a weight on one end always pulls more strongly there than on the other."
The scientists have designed their experiment to correspond to this detachment process. They apply a single layer of the polymer to a titanium surface. Using the titanium tip on an atomic force microscope, which only measures a few nanometers, they pick up a single chain of the polymer in the same way someone would pick up a thread from a table with their finger. Then they pull the tip away from the surface and measure the force required. They need 67 piconewtons to break the bond between the titanium surface and a dopa group on the polymer. As the polymer itself behaves like a loose spring, the force hardly falls before the next bond is broken, but remains almost constant.
The researchers now want to use the findings from this experiment to manufacture polymers with binding sites for different materials. The newly established Max Planck Graduate Center will be particularly suitable in future for pursuing this area of research as it will specialize in interdisciplinary projects of this nature.