Little Mohamed Western

What is the secret behind the superior strength of cobwebs, which outweigh most other metals despite their light weight? Scientists from the universities of Würzburg and Mainz say they have found an answer to this question.

They have shown that a natural amino acid called methionine provides elasticity to the proteins that make up cobwebs, increasing their durability. The scientists published their findings in the journal Nature Communication on September 26.

Spider silk
"Spider silk is one of the strongest materials in nature. It is stronger than high-tech fibers such as Kevlar or carbon," says Hans Neueller of the University of Würzburg, the lead author of the study. "This unique combination of durability and flexibility makes it extremely attractive in industry." Whether in aviation, the textile industry or medicine, the potential applications of these salient materials are numerous.

"We have discovered that spider filaments take advantage of a specific amino acid called methionine, to bind silk proteins tightly in a way previously unknown," he said.

Although synthetic spider silk is already produced on an industrial scale and is used in many products, it is not yet able to simulate the excellent mechanical properties of natural silk; the results of this new study may contribute to improving the quality of rayon.

Synthetic spider silk is unable to simulate the excellent mechanical properties of natural silk (Reuters)

Properties of methionine
Different life forms are known to depend on proteins that are made up of a limited group of twenty different amino acids.

Natural amino acids can be divided into two groups based on the properties of their lateral chains.

Soluble water-loving side chains tend to be on the surface of the protein, where they are responsible for an almost unlimited range of functions.

Methionine belongs to a group of hydrophobic amino acids, but is rare in most proteins.The methionine side chain is exceptionally flexible compared to the side chains of the other 19 natural amino acids.

So far, molecular biologists and protein scientists have paid little attention to this amino acid, believing that the side chain of methionine within proteins has little functional significance.

Spider silk is one of the strongest materials found in nature.

Flexibility and durability
Neueller and his team proved that spiders harness this characteristic (flexibility) by placing large amounts of methionine into the peripheral amino bands of filament-forming proteins, where the amino acid conveys its elasticity to the entire structure of the domain, making it soft and stretchable.

Proteins are traditionally considered to be solid bodies, yet many recent research highlights the role of protein dynamics in their functioning. "Like an adjustable key that adapts its shape to the lock, the ranges of silk proteins change their shape to communicate tightly with one another," the lead researcher says, greatly enhancing the bonding power of the peripheral fields.

Researchers expect these new findings to have implications for the design and development of new proteins, as well as in materials science, and believe that it is artificially possible to add amino methionine to the internal components of proteins, such as in spider filaments, to improve their functions or even create new ones.

The mechanical properties of synthetic materials can also be controlled by artificially adjusting the amount of methionine inside the silk protein.

Neueller and his team plan to conduct comparative studies on the effect of methionine on silk proteins on other spiders and silk glands, as well as experiments to incorporate methionine into the proteins of other organisms, with the aim of modifying their functions and possibly improving them.