ELECTRON-MICROSCOPIC INVESTIGATION ON THE FiBRIL STRUCTURE OF THE SILK FIBRES

Abstract

When domestic and wild silkworm cocoon fibroin fibre, from which sericin has been completely removed, is observed under the electron microscope, while it is being moderately broken down with hydrogen peroxide or sodium hydroxide, 400-600 Å diameter fibrils, formed by a large number of 100-150 Å diameter and 0.2-0.4μ diameter, 0.6-0.8μ width sparse fibrils were noticed. During the fibre break-down process, regardless whether it is domestic or wild cocoon fibre, 0.2-0.4μ diameter fibrils possess a characteristic of developing into band-form fibrils of 1.0-1.2μ width when treated with hydrogen peroxide or sodium hydroxide. With the exception of wild silkworm and one group of the domestic cocoon (Kuniichi, Kuniichikai, Koishimaru, Chinese etc), the middle layer fibroin fibre of the common domestic cocoon is weak against chemicals such as hydrogen peroxide and sodium hydroxide, different from those the outer and inner layer fibroin fibres.The following is on the detail electron microscopic study of fibroin fibre fibrilization based on the observations of fibre cross-section of replica test material.The results on the cross-sections of cocoon fibre and sericin-free fibroin fibre being that much finer, comparatively uniform fibroin of 0.2-0.4μ diameter fibrils and 0.6-0.8μ width fibrils, totalling around 1, 000 were noticed, compared to the fibril 0.3-3μ diameter noticed under the ordinary microscope. In order to observe the fibril structures more accurately, the cross-section was treated gradually and broken down with ten per cents solution of hydrogen peroxide or one normal solution of sodium hydroxide the results being that still finer, fibrils of 400-600 Å diameter were accurately observed.