2018 年 74 巻 5 号 p. 95-108
Fundamental dissolution behavior of liquid silk (LS) gel taken out from the fully grown larva of Bombyx mori silkworm into water, and the influence of complex formations between fibroin and sericin fractions, were investigated. WAXD measurements of the “sea-island”-structured as-cast gel films revealed,after annealing, that the fibroin-rich “island”portion formed a stable silk 1 structure while the “sea”portion has been transformed from the amorphous into a silk 2 crystal structure at room temperature without any external shear force. For the fibroin phase, however, a very long relaxation time was required to obtain the silk 2 modification. We have studied the influence of the interaction between fibroin and sericin on the crystal modification directly in the lyophilized silk gland of the fully grown larva of Bombyx mori. In the posterior silk gland, the fibroin formed a silk 1 structure according to the polymorphism property of fibroin. In the middle silk gland where sericin P fraction is to be secreted, fibroin showed silk 2 crystal diffraction. Following the secretion of sericin P fraction, the sericin M fraction has become secreted indicated by definite silk 1 crystal diffraction. However, silk 2 crystal diffraction remained almost unchanged, which means that sericin M fraction has a potential to regulate the crystal transformation of fibroin. Furthermore, influence of the modulation of spinning process or the addition of metal ions into a LS aqueous solution in flow state on the formation of fiber structure was investigated.
