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  • The Internal Structure of t...
    Baer, Alexander; Hoffmann, Ingo; Mahmoudi, Najet; Poulhazan, Alexandre; Harrington, Matthew J.; Mayer, Georg; Schmidt, Stephan; Schneck, Emanuel

    Small (Weinheim an der Bergstrasse, Germany), June 1, 2023, 2023-06-00, 20230601, Volume: 19, Issue: 22
    Journal Article

    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. Small‐angle neutron scattering reveals the nanoscale organization of velvet worm slime. The rapid, mechanically induced transition of this liquid bioadhesive into stiff fibers is based on the self‐assembly of proteins that are freely localized in solution. Nanoglobules, the previously assumed storage units for these fiber precursors, only contain small amounts of proteins and lipids.