by Staff Writers
Munich, Germany (SPX) Oct 19, 2017
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 Bar, 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 Dusseldorf, 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
"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," Bar 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," Bar 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
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?
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.
Raleigh NC (SPX) Oct 18, 2017
New research from North Carolina State University, MIT and the University of Michigan finds that the surface texture of microparticles in a liquid suspension can cause internal friction that significantly alters the suspension's viscosity - effectively making the liquid thicker or thinner. The finding can help address problems for companies in fields from biopharmaceuticals to chemical manufactu ... read more
Space Technology News - Applications and Research
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