Tensile properties of Attacus atlas silk submerged in liquid media

Abstract

Tensile properties of Attacus atlas (Saturniidae) silk were measured in air, water, and ethanol. Control samples in air showed a large variability, so a normalization method was developed to enable comparison with the behavior of samples submerged in the liquid media. Amino acid analysis demonstrated that the composition of A. atlas silk is similar to that of silk produced by other members of the Saturniidae family. The tensile properties of A. atlas silk resemble those of Bombyx mori (common domesticated silkworm) silk, although the two silks have different compositions. In particular, the elastic modulus is decreased by immersion in water and increased slightly by immersion in ethanol. The behavior of A. atlas silk can be described in terms of water having a disruptive effect on proteinOprotein hydrogen bonds, whereas ethanol acts as a desiccant and therefore enhances proteinOprotein hydrogen bonding. There are significant differences between the tensile properties of A. atlas silk and spider (Nephila madagascarensis) drag line, even though these materials have similar amino acid compositions: the spider silk has previously been shown to exhibit a decreased elastic modulus and conspicuous supercontraction in both liquids. Primary composition is therefore not a simple indicator of mechanical function in silks.

The role of salt and shear on the storage and assembly of spider silk proteins

“…This leads us to suggest that shear forces are likely to play a greater role than salt effects during the fiber spinning process in vivo ( Casem et al, 2002, Knight and Vollrath, 2002, Perez-Rigueiro et al, 2001aand Perez-Rigueiro et al, 2001b.…”

Biocompatible Material from Indonesian Natural Resource of Wild Silkmoth Cocoon

“…The tensile test was conducted by following tensile test method for single silk fiber [16,17,18]. The 5 cm length of single fiber was glued in the cardboard frame with distance 30 cm (regarded as gauge length).…”

Structure and properties of ultrafine silk fibers produced by Theriodopteryx ephemeraeformis

“…The bag worm silks have much higher content of lysine, leucine, phenylalanine, threonine, cysteine, and histidine than B. mori and the common wild silks. The amino acids glycine, alanine, serine, and threonine are reported to be in the crystalline region whereas the other amino acids are reported to be in the amorphous region for B. mori silk [2,3,17,18]. The ratio of glycine/alanine is reported to determine the crystallographic form of the proteins.…”

“…The glycine/alanine ratio of bag worm silk fibers is 0.27, but 1.52 for B. mori silk fibers indicating that the bag worm silk should have a considerably different crystallographic form [19,20]. The ratio of amino acids in the crystalline and noncrystalline region is referred to as the disorder ratio and is related to the tensile properties and hydrophilicity of the fibers [18]. Disorder ratio of bag worm silks is 0.18, much lower than the ratio for B. mori silk (6.7) suggesting that bag worm silk will have inferior tensile properties compared with B. mori silk.…”