The Internal Structure of the Velvet Worm Projectile Slime: A Small-Angle Scattering Study |
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Authors: | Alexander Baer Ingo Hoffmann Najet Mahmoudi Alexandre Poulhazan Matthew J. Harrington Georg Mayer Stephan Schmidt Emanuel Schneck |
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Affiliation: | 1. Department of Zoology, Institute of Biology, University of Kassel, D-34132 Kassel, Germany;2. Spectroscopy Group, Institut Laue-Langevin, 38000 Grenoble, France;3. Small-Angle Neutron Scattering Group, ISIS Neutron & Muon Source, STFC Rutherford Appleton Laboratory, Didcot, OX11 0QX UK;4. Department of Chemistry, University of Quebec at Montreal, Montreal, QC, H2X 2J6 Canada;5. Department of Chemistry, McGill University, Montreal, QC, H3A0B8 Canada;6. Chemistry Department, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany;7. Physics Department, Technische Universität Darmstadt, D-64289 Darmstadt, Germany |
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Abstract: | For prey capture and defense, velvet worms eject an adhesive slime which has been established as a model system for recyclable complex liquids. Triggered by mechanical agitation, the liquid bio-adhesive rapidly transitions into solid fibers. In order to understand this mechanoresponsive behavior, here, the nanostructural organization of slime components are studied using small-angle scattering with neutrons and X-rays. The scattering intensities are successfully described with a three-component model accounting for proteins of two dominant molecular weight fractions and nanoscale globules. In contrast to the previous assumption that high molecular weight proteins—the presumed building blocks of the fiber core—are contained in the nanoglobules, it is found that the majority of slime proteins exist freely in solution. Only less than 10% of the slime proteins are contained in the nanoglobules, necessitating a reassessment of their function in fiber formation. Comparing scattering data of slime re-hydrated with light and heavy water reveals that the majority of lipids in slime are contained in the nanoglobules with homogeneous distribution. Vibrating mechanical impact under exclusion of air neither leads to formation of fibers nor alters the bulk structure of slime significantly, suggesting that interfacial phenomena and directional shearing are required for fiber formation. |
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Keywords: | biopolymers mechano-responsive neutron scattering onychophora SDS-PAGE X-ray scattering |
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