A new silk: Mechanical, compositional, and morphological characterization of leafhopper (Kahaono montana) silk

The mechanical properties, amino acid composition, internal morphology, and solvent-induced interaction of silk produced by the endemic Australian leafhopper, Kahaono montana Evans (Hemiptera: Cicadellidae) were studied. Ion plasma etching/scanning electron microscopy examination of the internal morphology revealed a skin-core structure, with bands in the core region aligned regularly in a transverse direction to the fibre axis, separated by a nominal spacing of 100 nm. The internal structure of the silk was compared with those from spider Eriophora transmarina (Keyserling) (Araneida: Araneidae) radial thread and silkworm (Bombyx mori). The amino acid composition of K. montana silk was determined using HPLC, and was found to be dominated by small amino acids: Serine, alanine and glycine. The silk-solvent interaction was tested using selected aqueous, organic and surfactant solutions, and the solubility of the silk was found depend primarily on the pH and ionic strength of the solvent. Tensile tests showed that the silk has considerably weaker mechanical properties than spider silk and silkworm silk. The differences in mechanical properties of K. montana silk compared with spider and silkworm silk are attributed to the distinction in amino acid composition ratio and internal morphology, and are likely to reflect the functions of the silks in these species.