Abstract: In this contribution, the temperature-induced phase changes of the silk gland of Bombyx mori silkworm were studied using high-resolution ¹³C solid-state NMR spectroscopy. The silk gland samples were obtained from alive silkworms which were stored under either normal temperature or 6 ℃ for 2 weeks. The results showed that storing the alive silkworms at 6 ℃ could induce a phase transition in the fibroin gland in the middle and anterior parts of the middle division of the lumen, from an isotropic phase to an anisotropic liquid crystalline phase. Such phase transition was not observed in the silkworms stored under normal temperature. Previous studies have demonstrated, both experimentally and theoretically, lowering temperature can induce an action equivalent to a shearing stress in many elastic polymers (including proteins), and shearing stress may play an important role in the spinning of the silkworm. The results of this study suggest that lowering temperature or applying strong shearing may be used as ways to control the process to fabricate silklike fibers of high performance.

Key words: solid-state NMR, silk fibroin, phase transition, temperature