Discover the secret of spider silk stamina

Nam Hy Hoang Phong (translation & caption by Denise Brehm, MIT News)

Spider silk is a very durable material ⁽ⁱ⁾ made of protein & amino acid (amino acid). Scientists have known the toughness or strength of silk fibers in the amino acid content of fibers: the strength of dragline silk lies in the amino acid combined with the crystal to make the proteins strong and strong; while twisting silk is made from curled protein chains that make it elastic and elastic.

According to new disclosures published by researchers at MIT's Department of Environmental & Civil Engineering (CEE), the strength of biological materials such as spider silk lies in the characteristic structural geometry of proteins, including Many weak links between hydrogen atoms work together to withstand the effects of tension & weight, containing potential strength.

This structure makes natural matter light but solid like steel even when the hydrogen bond between the fibers is very weak, 100 to 1000 times weaker than the bond in metal or horizontal crystals. equals covalent bonds in artificial fibers Kevlar ⁽ⁱⁱ⁾ .

The image illustrates the structure of a beta protein array, a combination of telethonin Z1-Z2, within a giant protein titin bundle ⁽ⁱⁱⁱ⁾ . The right magnification shows the strength of three beta protein strands (purple) with hydrogen bonds (yellow), helping them to bond. Buehler and Keten explain that hydrogen bonding in the beta array structure binds three or four bundles, even in many links. (Photos: Sinan Keten and Markus Buehler, source of web.mit.edu)

Based on the theory of macromolecular simulation model made by super-powerful computer, the research team has given new and accurate insights on how protein structure increases material durability, helps engineers create new materials that mimic fragile but very strong spider silk threads. This also affects research on tissue tissue in the cell & amyloid fiber structure ^(iv) in brain tissue. 'We hope that the understanding of the mechanism of molecular materials will be able to help us create a guiding principle for synthesizing new materials,' said Professor Markus Buehler, who leads the team. study said.

In the article published February 13 in the online Nano Letters, Buehler & graduate student Sinan Keten described how they used molecular models to explain three or four hydrogen bonding clusters connected to clusters. Short beta fibers & overlap in a piece of protein structure when placed under a mechanical pressure ^(v) . This type of structure allows proteins to withstand greater forces when beta fibers have only one or two bonds. Oddly, the small bundles withstand more weight than beta strands with lots of hydrogen bonds.

'The protein structure made up of one or two hydrogen bonds will create very small mechanical strength, because hydrogen bonding is very weak & easily broken without nearly stimulating , ' Buehler explained. Esther and Harold E. Edgerton, two assistant professors at CEE said: 'But when using three or four bonds, strength even surpasses the strength of many metals. Using more than four links will lead to a lot of endurance degradation. Maximum strength with three or four links' .

After observing the concurrent faults of hydrogen bonding clusters in the structure of protein molecular simulation model ^(vi) . Buehler and Keten wanted to find out why the bonds invaded in small clusters, even in long strands with lots of hydrogen bonds. They use the law of thermodynamics to explain unusual phenomena. The article in Nano Letters describes how external forces change the energy entropy in the system leading to the breakdown of hydrogen bonds. By calculating the energy needed to initiate the disruption process spread in a protein molecule, they explained that adding more hydrogen bonds in longer fibers could not increase the durability of the material. .

'You can imagine a long string of beta beta with weak links that will not create strength for each component,' Keten said. 'But a material with a lot of short beta strands and connected to three or four hydrogen bonds can create greater strength than steel. In many metals, energy is stored directly in many more stable bonds, ie metal bonds, even when the crystal state is broken down. In proteins, everything is complicated by entropic elasticity like twisted noodles and the natural collaboration of hydrogen bonds'.

Beta plaques with many short filaments attached to three or four hydrogen bonds are common structural forms in all beta protein structures. Protein resistance is a key evolution, driven by nature's creative step."The metals are shaped by many strong bonds, so it takes a lot of energy to break down ," Buehler said. 'However, crystal meshes of metal structures are never perfect; including many disadvantages that reduce the durability of materials. Metals can reveal disadvantages like cracking when you put on them a load. In the beta protein array, the natural limit of hydrogen bonding groups helps to dissipate energy due to external forces without reducing material strength. This shows the ingenious and effective mysteries of natural materials'.

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Note

• ⁽ⁱ⁾ : See also the comparison table of durability of some materials. Data provided by Gosline, according to Randolph V. Lewis, Department of Molecular Biology, University of Wyoming.

Material Durability Energy needed to break the bonds (N m ^-2 )

(J kg ^-1 )

Silk 1 x 10 ⁹

1 x 10 ⁵

Kevlar 4 x 10 ⁹

3 x 10 ⁴

Rubber 1 x 10 ⁶

8 x 10 ⁴

Ribbed 1 x 10 ⁹

5 x 10 ³

• ⁽ⁱⁱ⁾ : Kevlar is a registered trademark of yarn for para-aramid artificial fiber, which is very stable and light. Kevlar was developed at Dupont Company in 1965 by by Stephanie Kwolek and Roberto Berendt, commercialized since the early 70s of the last century.

• ⁽ⁱⁱⁱ⁾ :

See more about the overview model of Titin Z1Z2 complex - Telethonin. The left sample shows that the surface landscape of titin Z1Z1 - telethonin is illustrated with a close contact surface between telethonin (yellow) & two titin molecules (red and blue). The right sample shows the binary pairing of two pairs of Z1Z2 on either side of the telethonin molecule. The theoretical model of the original structure of titin Z1Z2 - telethonin from biophysical perspective, built by a computer, was proposed by the Beckman Research Institute at the University of Illinois at Urbana-Champaign. (Photo: www.ks.uiuc.edu)

• ^(iv) : amyloid fibers (amyloid fibers). Amyloid is an insoluble set of protein fibers that share distinct point structures. Abnormal superposition of amyloids in organs can lead to amyloidosis and may play different roles in neurodegenerative diseases such as Alzheimer's disease.

• ^(v) : The telethonin molecule has a circular structure that overlaps, so this protein fragment is removed by cutting off the telethonin molecule in a horizontal direction rather than cutting the telethonin molecular length into each segment.

• ^(vi) : Video process of cutting off hydrogen bonds. The video shows the fracture process of the beta array model system. The middle yarn is pulled at a constant speed, the hydrogen bonds in the broken bundle lead to the failure of beta arrays when subjected to a great stretch.