Chemical structure and physical properties of antheraea assama silk

Abstract

SYNOPSISThis work deals with the chemical composition, physical structure, and thermal behavior of Antheraea assama silk fibers. The amino acid composition is characterized by the high content of alanine, glycine, and serine. Among the amino acid residues with polar side chains, aspartic acid, arginine, and tyrosine prevail. The birefringence and isotropic refractive index values are 0.030 and 1.557, respectively. The stress-strain curve shows a yield point at 5% elongation, followed by a region of gradual extensibility. Elongation at break is about 40%. The X-ray diffraction pattern is typical of p silks, with -(ala),-repeats in the polypeptide sequences of the crystalline regions. The differential scanning calorimetry curve shows two minor endotherms at 230 and 300°C, before final thermal decomposition a t 362°C. The maximum extent of contraction exhibited by the thermomechanical analysis curve is 2%. The surface of degummed fibers shows the presence of longitudinal striations. The fiber cross section is mostly elliptical. Raw fibers taken from cocoons show the presence of several crystalline deposits on the surface, identified as crystals of calcium oxalate.

Studies on Indian silk. I. Macrocharacterization and analysis of amino acid composition

“…The proportion of alanine is about 34% in tasar, 36% in eri, and 35% in muga. This value is consistent but is lower than that reported by Freddi et al, 11 particularly for muga (ϳ 44%). On the other hand, the glycine content in these varieties is about 27-29%, which is lower than that found in the mulberry varieties (ϳ 43%).…”

“…Muga was shown to have the least, with 67.77%. In a study on chemical composition and physical properties of Antheraea assama silk, Freddi et al 11 reported a high alanine content of 42.62% and very low arginine content (2.83%), although cystine (0.34%) was present and the other sulfur-containing amino acid, methionine, was not detected in their analysis.…”

Study on the microstructure of African wild silk cocoon shells and fibers

“…The functional adaptations of these crystals and the colour of cocoons range from camouflage to heat absorption or light transmission [12]. Other wild silk cocoons, such as A. assama, also showed the presence of calcium oxalate crystal deposits on their surface [13]. The difference in the size and shape of the crystals suggests the role they might have on influencing the texture of the cocoon surface.…”

A novel method to prepare tussah/Bombyx mori silk fibroin-based films

“…The amino acid sequence in the crystalline region of BSF and TSF was considered to be (GAGAGS)n (G: glycine, A: alanine, S: serine) and -(ala)-, respectively. 44,45 So the TSF molecular chains would form a more compact crystalline structure than BSF, resulting in higher thermal decomposition peaks (Fig. 5).…”