PRESENCE OF α-HELICAL PORTION OF <i>Bombyx mori</i> SILK FIBROIN

Investigations have been made on the molecular conformation in the solid state of Bombyx mori silk fibroin and the model polypeptides by an infrared spectroscopy (IR).An IR absorbed band assigned to silk I type conformation was only found for the precipitates not having any random coil obtained by an enzyme treatment to the middle silk gland diluted with water and by dissolving silk fibers in an aqueous LiBr solution. On the other hand, the IR absorbed band assigned to α-helical conformation was found together with those of random coil and the silk II type conformation for as-polymerized model polypeptides and silk fibroin threads hydrolyzed by aqueous HCI solution.It is, therefore, concluded that a small amount of α-helix exists in the amorphous part of Bombyx mori silk fibroin.