Research ArticleBIOPHYSICS

Proton conductivity in ampullae of Lorenzini jelly

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Science Advances  13 May 2016:
Vol. 2, no. 5, e1600112
DOI: 10.1126/sciadv.1600112
  • Fig. 1 The AoL.

    (A and B) Skates and sharks locate their prey by detecting the weak electric fields naturally generated by biomechanical activity. (C) A network of electrosensory organs called the AoL is responsible for this sense. (D) An individual ampulla consists of a surface pore connected to a set of electrosensory cells by a long jelly-filled canal. Sharks and skate can sense fields as small as 5 nV/cm despite canals traveling through up to 25 cm of noisy biological tissue. (E) A sample of the AoL jelly on an electrical device is presented. Scale bar, 0.5 mm.

  • Fig. 2 Proton conduction in ampullae jelly.

    (A) Palladium hydride (PdHx) protode behavior. Under an applied voltage, PdH contacts split into Pd, H+, and e. Protons are injected into the skate jelly, whereas electrons travel through external circuitry and are measured. (B) Transient response to a 1-V applied signal in AoL jelly from R. rhina. The proton current (red) is 50 times larger than the ion current (blue). The electron current (black) is slightly smaller than the ion current. (C) Four-point probe geometry. Distinct Au contacts are used to measure voltage within the channel and to correct for any potential drop at the PdH-jelly interface. (D) Four-point probe conductivity results from R. binoculata. Conductivity increases exponentially with voltage up to about 1 V, suggesting that conduction is limited by potential barriers. Deuterium conductivity (green) at 90% D2O humidity (RD) is half as large as proton conductivity (red) for all voltages. Ion conduction in the hydrated state (blue) is minimal. (E) TLM geometry. Varying the distance between source and drain (LSD) distinguishes between the fixed PdH-jelly interface resistance and the varying bulk resistance. (F) RLN as a function of LSD for R. binoculata. A linear fit gives a bulk material proton conductivity of 1.8 ± 0.9 mS/cm.

  • Fig. 3 Chemical characterization of jelly.

    (A) Structure of KS, which may be present in the skate (R. binoculata) AoL jelly. Proton conduction in a sulfated polymer is consistent with known conducting materials, such as Nafion or modified chitosan. (B) Compositional analysis of skate jelly from R. binoculata. The peaks denote the presence of different monomers (GalNH2, galactosamine; GlcNH2, glucosamine; Gal, galactose; Glc, glucose; Man, mannose; GlcA, glucuronic acid). Glucosamine and galactose, the two components of KS, are found in highest abundance. An equimolar ratio of glucosamine to galactose would be expected for KS; the slightly higher abundance of glucosamine suggests the presence of other polysaccharides in the jelly. (C) Full-scale FTIR spectrum of the skate jelly showing characteristic peaks of sulfated glycosaminoglycans (GAGs), specifically KS. a.u., arbitrary units.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/5/e1600112/DC1

    fig. S1. Collection of AoL jelly.

    fig. S2. TGA of AoL jelly.

    fig. S3. Cross-species consistency of results.

    fig. S4. Control experiments on Nafion.

    table S1. Elemental analysis of AoL jelly as analyzed by Intertek Pharmaceutical.

    table S2. Room-temperature proton conductivities of Nafion and known biopolymers.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Collection of AoL jelly.
    • fig. S2. TGA of AoL jelly.
    • fig. S3. Cross-species consistency of results.
    • fig. S4. Control experiments on Nafion.
    • table S1. Elemental analysis of AoL jelly as analyzed by Intertek Pharmaceutical.
    • table S2. Room-temperature proton conductivities of Nafion and known biopolymers.

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