US, Slovenian scientists discover new protein in toughest spider silk

Ljubljana, 14 August - A group of US and Slovenian scientists researching the toughest biological material - the dragline silk produced by Darwin's bark spider - have discovered a new protein, which they believe helps to make it so unusually strong.

Darwin's bark spider.
Photo: Courtesy of Matjaž Gregorič

Darwin's bark spider.
Photo: Courtesy of Matjaž Gregorič

The team had tried to establish why the dragline silk made by Darwin's bark spider's (Caerostris darwini) is of such high quality compared to those of other spiders.

It has better extensibility than any other biological material and better than many synthetic materials.

Matjaž Gregorič from the Jovan Hadži Institute of Biology at the ZRC SAZU in Ljubljana has explained for the STA that spider silk is made mostly of proteins.

It is usually made of two proteins - MaSp1 in MaSp2, but the US and Slovenian researchers discovered a third protein in this spider, which they named MaSp4a.

The new protein has regions for which the scientists assume contribute to Darwin bark spider's dragline silk's greater degree of elasticity.

The researchers also established that this spider's silk glands and spinning ducts have special features which differ from the ones studied so far, says Gregorič.

They assume this also plays a major part in the dragline silk's durability, which enables the spider to produce giant orb webs.

The team was led by Jessica E. Garb from the US University of Massachusetts Lowell, featuring two Slovenians, apart from Gregorič also Matjaž Kuntner from the National Institute of Biology and the Jovan Hadži Institute of Biology. They published their findings in the Communications Biology journal.

There is a lot of research into spider silk, focussing on the patterns of its evolution and the genetic structure as well as on ways of synthesising it in laboratories.

Gregorič says that "at the moment it's hard to imagine the scope of its potential application once we can successfully make it in a lab".

He believes it could be used in a number of areas where elastic but durable materials are needed, including clothes and shoe production, food packaging, car tyres, military equipment, parachutes, ropes, various tools, 3D printers, etc.

Silk being a biocompatible material, it could also be very useful in medicine. It could for instance be used for natural stitches, as a support for nerve regeneration, or as a delivery vehicle in biodegradable capsules.