Control of Crystallinity in Wild-Type Silk Antheraea pernyi

Silk has become a popular biomaterial due to its biodegradability and the favorable mechanical and thermal properties of the protein, silk fibroin (SF), constituting the silk fiber [1]. These properties arise from the crystalline secondary structure, β pleated sheets, the fraction of which has great implications on SF’s potential usage. Most research on SF has been performed on domesticated Bombyx mori (BM) SF, leaving the potential applications of wild silks largely unexplored. Therefore, this study investigates the crystallinity and thermal properties of a byproduct formed during the processing of wild-type Antheraea pernyi (AP) SF, a suspension of AP SF particles in DI water. This suspension was exposed to conditions known to induce β sheet formation in SF films (methanol and water vapor annealing) [2]. The crystalline and thermal properties were then investigated with respect to the conditions. The β sheet fraction was determined through Fourier Transform Infrared Spectroscopy, while the crystal structure was analyzed using Wide Angle X-ray Scattering. Thermal properties such as the glass transition temperature (Tg) and heat capacity step at Tg, were obtained using Differential Scanning Calorimetry.

[1] Hu, Xiao, et al. “Determining beta-sheet crystallinity in fibrous proteins by thermal analysis and infrared spectroscopy.” Macromolecules, vol. 39, no. 18, 2006, pp. 6161–6170, https://doi.org/10.1021/ma0610109

[2] Hu, Xiao, et al. “Regulation of Silk Material Structure by Temperature-Controlled Water Vapor Annealing.” Biomacromolecules, 2011,12(5):1686–1696.