STUDIES ON THE FINE STRUCTURE OF SILK FIBROIN

Abstract

The silk glands of matured tussah silkworms were dried under various conditions. X-ray diffraction patterns of coagulated silk fibroin of those silk glands were examined in comparison with those of silk gut and poly-L-alanine fiber. Their features are summarized as follows:1) As for silk fibroin from the posterior divison of silk gland, the striking change in its X-ray patterns was observed when it was dried at 50°C or over. It showed a pattern typical of unoriented aggregation of β-form crystallites.2) When dried at room temperature, silk fibroin gives the pattern which might be considered as indicating an unoriented α-helical structure in the posterior division of silk gland, and unoriented fiber structure (β-form), in the anterior division of silk gland.3) Silk fibroin shows X-ray pattern typical of the β-form after being dipped in a polar solvent like alcohol and dried.4) X-ray diffraction patterns of silk fibroin from the posterior division of silk gland dries at less than 56°C indicates the presence of a broard 7.4 A reflection. From comparative examination on the X-ray patterns of silk gut and poly-L-alanine fiber, and on the infrared spectra of silk fibroin films, it seems that the fibroin molecule container some α-helical conformation mingled in random coil structure.