18-Oct-2017 - Max-Planck-Institut für Kolloid- und Grenzflächenforschung

Stiff fibres spun from slime

Nanoparticles from the secretion of velvet worms form polymer fibres that can be recycled in water

Nature is an excellent teacher – even for material scientists. Researchers, including scientists at the Max Planck Institute of Colloids and Interfaces, have now observed a remarkable mechanism by which polymer materials are formed. In order to capture prey, velvet worms shoot out a sticky secretion that stiffens into strong threads under the action of force. The extraordinary thing about these threads is that they can be dissolved and then reformed again. The fact that reversible polymer fibres can be drawn from the previously liquid secretion is a very interesting concept for researchers. It is quite possible that one day it will be possible to synthesize novel recyclable materials based on the principle of velvet worms.

Some animals produce amazing materials. Spider silk, for example, is stronger than steel. Mussels secrete byssus threads, which they use to cling tightly to stones under water. The material secreted by velvet worms is no less impressive. These small worm-like animals, which look like a cross between an earthworm and a caterpillar, spray a sticky liquid to ward off enemies or catch prey that is particularly deadly for prey such as woodlice, crickets and spiders: As soon as they try to wriggle out of the slimy threads, their struggles cause the threads to harden, leaving no hope of escape.

“The shear forces generated by the prey’s struggles cause the slime to harden into stiff filaments,” explains Alexander Bär, a doctoral student at the University of Kassel, who is studying under the velvet-worm expert Georg Mayer. In order to investigate the slime of an Australian velvet worm species, the biologist worked closely with researchers from the Max Planck Institute of Colloids and Interfaces in Potsdam. The chemist Stephan Schmidt, for example, now a junior professor at Heinrich Heine University in Düsseldorf, helped to elucidate the nanostructure of the slime. A research group headed by biochemist Matt Harrington in the Biomaterials Department of the Potsdam Institute focused on other questions concerning the chemical composition and molecular processing. The interdisciplinary group of scientists was particularly interested in how the composition and structure of the secretion changes during thread formation.

Slimy mix of proteins and fatty acids

“We had already known that the slime consists mainly of large protein molecules and fatty acids,” Alexander Bär says. At the Max Planck Institute in Potsdam, the researchers discovered that the proteins and lipids combine to form tiny globules. “Velvet worms produce the protein and fat molecules as well as other components separately”, Bär explains. “Outside the gland cells, the nanoglobules then form independently to create the thread-forming and adhesive properties.” The globules are formed with remarkable precision in that they are uniform in shape and always around 75 nanometres in diameter.

Velvet worms store their liquid weapon until it is needed. They then shoot the slime at their prey or foe through two glands located on either side of their head by means of muscular contractions. “At first the sticky consistency does not change,” Bär says. “However, as soon as the prey begins to struggle, shear forces act on the slime to rupture the nanoglobules.” Vibrational spectroscopy studies in Potsdam showed that proteins and fatty acids separate in the process. “Whereas the proteins form long fibres in the interior of the slime, the lipid and water molecules are displaced to the outside and form a kind of sheath,” Bär explains. The researchers also found that the protein strand inside has a tensile stiffness similar to that of Nylon®. This explains the remarkable performance of the filaments.

Polymerized threads dissolve in water again

Further experiments showed that the polymerized slime threads can be dissolved in water again within a few hours of drying. “The astonishing thing for us was that the proteins and lipids evidently mix again to form the same nanoglobules we had already found in the original slime,” Matt Harrington says. The newly formed protein-lipid globules were even similar in size to those in the natural secretion. “Evidently, a mechanism of self-organization is at work which we do not yet fully understand,” Harrington says.

Another startling discovery was that sticky threads can be drawn again from the recovered slime. And they behaved exactly like freshly secreted velvet-worm secretion under the influence of shear forces: they hardened. “This is a nice example of a fully reversible and indefinitely repeatable regeneration process,” says Matt Harrington. Intriguingly, this is all accomplished with biomolecules and at normal ambient temperatures. Velvet worms could therefore serve as a model for manufacturers of synthetic polymers and could conceivably teach them a lot about the sustainable production of synthetic materials.

Harrington agrees. The biochemist can well imagine that one day we will be able to synthesize macromolecules for industrial applications in a similar manner based on renewable raw materials. In the case of spider silk, it has already been possible to produce analogous proteins industrially and to supply the fibres produced from them to the garment industry.

How are proteins and lipid molecules separated?

A polymer that dissolves in water, like the solidified threads of velvet worms, would probably be impractical. But the principle could generate new inspirations in materials science, Matt Harrington believes. “At the moment, the first step is to understand the mechanisms better,” says the biomaterials specialist, who has now begun a professorship at McGill University in Montreal. For example, the scientists are interested in why mechanical shear forces cause the proteins to separate from the lipid molecules in the first place. They also want to determine the factors that govern the reversible formation of nanoglobules of uniform size. Another unanswered question is how the protein units combine to produce rigid fibres without forming fixed chemical bonds, says Max Planck researcher Harrington.

  • Alexander Baer, Stephan Schmidt, Sebastian Haensch, Michaela Eder, Georg Mayer und Matthew J. Harrington; "Mechanoresponsive lipid-protein nanoglobules facilitate reversible fibre formation in velvet worm slime"; Nature Communications; 17. Oktober 2017

Facts, background information, dossiers

  • proteins
  • vibrational spectroscopy

More about MPI für Kolloid- und Grenzflächenforschung

  • News

    In milliseconds from polluted to clear water

    Researchers at the Max Planck Institute of Colloids and Interfaces developed a membrane that is composed of a bundle of nanometer-sized tubes. They used it as a nanoreactor to convert water marked with methylene blue into clear water in milliseconds using sunlight as a driver. ‘Running reac ... more

    Green Chemistry: Sustainable p-xylene production

    Lemonade, juice and mineral water often come in PET bottles. While these are practical and functional, their production is complex and not necessarily sustainable. The starting material for terephthalic acid, which is used to produce saturated polyesters such as PET (Polyethylene terephthal ... more

    Put into the right light - Reproducible and sustainable coupling reactions

    A team of researchers reports in the journal Nature Catalysis that sustainable carbon-nitrogen cross-couplings can be performed using simple nickel salts, carbon nitrides and light. The chemists study the use of cost-effective and reproducible semiconductors as photocatalysts in coupling re ... more

  • q&more articles

    With Light in the Fight against Malaria

    Malaria represents a global threat to health, which is difficult to keep under control. Amongst more than 200 million sufferers, over 500,000 die each year of the disease, with the risk of a fatal outcome being particularly high in children [1]. more

  • Authors

    Dr. Daniel Kopetzki

    born 1983, studied chemistry at the University of Regensburg and received his doctorate from the Max Planck Institute of Colloids and Interfaces in Potsdam, in the Department of Colloid Chemistry. Since Sept. 2011, he has been working as a post-doctoral fellow for Prof. Dr. Seeberger at the ... more

    Prof. Dr. Peter Seeberger

    born 1966, studied chemistry at the University of Erlangen-Nuremberg, and received his doctorate in biochemistry from the University of Colorado. After holding a post-doctorate position at the Sloan-Kettering Institute for Cancer Research in New York City, he was Assistant Professor and Fir ... more

More about Max-Planck-Gesellschaft

  • News

    Pumping up the music of molecules

    Sensitive animal noses can sniff out trace particles, such as volatile organic compounds, in the ambient air. Humans, on the other hand, are developing innovative technologies for this purpose, such as optical spectroscopy. This uses laser light to detect the molecular composition of gases. ... more

    How to find marker genes in cell clusters

    The thousands of cells in a biological sample are all different and can be analyzed individually, cell by cell. Based on their gene activity, they can be sorted into clusters. But which genes are particularly characteristic of a given cluster, i.e. what are its “marker genes”? A new statist ... more

    Cell-culture breakthrough: Advanced “mini brains” in the dish

    “Outer Radial Glia” (oRG) cells are nervous system stem cells that are instrumental for the development of the human cortex and have been challenging to produce in the lab. Now, a team of Max Planck researchers from Berlin succeeded in generating brain organoids that are enriched with these ... more

More about McGill University

  • News

    New 'chemical noses' to rid the environment of industrial pollutants

    Scientists from five European countries have joined forces to develop next-generation 'chemical noses' to remove industrial pollutants from the environment. The European Commission allocated 2.9 million euros to finance the Horizon2020 FET-OPEN project INITIO that will bring together resear ... more

    No more 'superbugs'?

    Antibiotics save lives every day, but there is a downside to their ubiquity. High doses can kill healthy cells along with infection-causing bacteria, while also spurring the creation of "superbugs" that no longer respond to known antibiotics. Now, researchers may have found a natural way to ... more

    The brain starts to give up its secrets

    A research team, led by the Research Institute of the McGill University Health Centre (RI-MUHC) in Montreal, has broken new ground in our understanding of the complex functioning of the brain. The research, which is published in the current issue of the journal Science, demonstrates that br ... more

q&more – the networking platform for quality excellence in lab and process

The q&more concept is to increase the visibility of recent research and innovative solutions, and support the exchange of knowledge. In the broad spectrum of subjects covered, the focus is on achieving maximum quality in highly innovative sectors. As a modern knowledge platform, q&more offers market participants one-of-a-kind networking opportunities. Cutting-edge research is presented by authors of international repute. Attractively presented in a high-quality context, and published in German and English, the original articles introduce new concepts and highlight unconventional solution strategies.

> more about q&more

q&more is supported by: