Tussah silk fibroin

Tanaka, T., Magoshi, J., Magoshi, Y., Lotz, B., Inoue, S. I., Kobayashi, M., Tsuda, H., Becker, M. A., Han, Z., and Nakamura, S. (2001). Spherulites of Tussah silk fibroin. Structure, thermal properties and growth rates./. Therm. Anal. Calorimetry 64, 645-650. 

Tsukada, M., Freddi, G., Gotoh, Y., and Kasai, N. (1994). Physical and chemical-properties of tussah silk fibroin films. / Polym. Sri. B Polym. Phys. 32, 1407-1412. 

Marsh, R. E., Corey, R. B., and Pauling, L. (1955a). The structure of Tussah silk fibroin. 

A detailed structure for Tussah silk fibroin has been derived which is in agreement with the X-ray diffraction data. The structure is similar to that of Bombyx mori fibroin in that it is based on anti-parallel-ohain pleated sheets the method of packing of the sheets, however, is quite different. 

In the current investigation, a detailed structure for Tussah silk fibroin has been derived which is compatible with both chemical and X-ray data. This structure also has strong impUcations concerning the structure of the (stretched) form of XM>ly-i,-alanine. 

Table 2. Spaeings and relative intenaitieg for equatorial reflections for Bombyx mori and Tussah silk fibroins...

Packing drawings of the pseudo structure of Tussah silk fibroin are shown in Fig. 3. Within each pleated... 

We can now see how the differences in the structures of Bombyz mori and Tussah silk fibroins are related to the striking differences in their chemical compositions. The principal difference between the pseudo structures of the two silks is in the method of packing... 

The structure of tussah silk fibroin (with a note on the structure of b-poly-L-alanine). Acta Cryst. 8 (1955) 710-715. (Richard E. Marsh, Robert B. Corey, and Linus Pauling). (SP 110 ... 

M Tsukada, G Freddi, P Monti, A Bertoluzza, N Kasai. Structure and molecular conformation of Tussah silk fibroin films Effect of methanol. J Polym Sci B Polym Phys 33 1995—2001, 1995. 

A scaffold was described which is a nanostructured composite with a core made of a composite of hydroxyapatite and tussah silk fibroin (15). The core is encased in a shell of tussah silk fibroin. The composite fibers were fabricated by coaxial electrospinning using green water solvent. 

In comparison to nanofibers of pure tussah silk, the composite notably improved the mechanical properties, with a higher initial modulus and breaking stress. It was found that the fiber scaffold supported both the cell adhesion and the proliferation, and also functionally promoted alkaline phosphatase and mineral deposition relevant for biomineralization. The composites are more biocompatible than pure tussah silk fibroin or cover slip (15). 

Some natural fibrous proteins and sequential model polypeptides have been used as follows (1) Tussah Antheraea perni silk fibroin [a-helix form], (2) Bombyx mori silk fibroin [silk I and II forms], (3) poly(L-alanyL-glycine) [Ala-Gly]i2 [silk I and II], (4) collagen fibril [triple-strand helix], and (5) poly(L-prolyl-L-alanyL-glycine) [Pro-Ala-Gly [triple-strand helix]. 

Figure 31 shows the 300 MHz H CRAMPS NMR spectra of three silk fibroins (A) Tussah Antheraea pernyi (a-helix), (B) Bomhyx mori-i (silk I form), and (C) Bomhyx mori- (silk II form) fibroins. They give highly resolved H CRAMPS NMR spectra in the solid state, which are the first high-resolution solid-state H CRAMPS NMR spectra of such natural proteins, as far as we know. The H signals of these fibroins are separated basically into four regions (H , side-chain phenyl, H, and side-chain protons). 

Fig. 32. 2D HETCOR NMR spectra of silk fibroins (A) Tussah Antheraea...

Gly a-helix, b = 84.7 silk I, b = 86.9). The peak intensity of the side-chain protons of Tussah Antheraea pernyi fibroin is higher than that of Bombyx mori, which can be explained in terms of the difference in L-alanine content between them. Thus, it is considered that the side-chain proton signals of the silk fibroins are associated mainly with the methyl protons of the L-alanine residues. Accordingly, we can easily distinguish between Tussah Antheraea pernyi (a-helix) and Bombyx mori-1 fibroins from the peak intensity ratio of against in the H CRAMPS NMR spectra. 

Now it is clear that the H chemical shift reflects the conformation of model polypeptide [Ala-Gly] 12 and natural silk fibroins such as Tussah Antheraea pernyi and Bombyx mori silk fibroins. It is confirmed that the well-defined [Ala-Gly] 12 is a suitable model for the structural study of natural silk fibroins (silk I and silk II forms) using high-resolution solid-state NMR. As a result, the H peak assignment of the silk fibroins on the basis of the conformation-dependent H chemical shifts of model polypeptides can be determined utilizing H CRAMPS NMR and H- C 2D HETCOR NMR, as described in this section. The chemical shift results of model polypeptides [Ala-Gly] 12 synthesized by Shoji et al. play an important role in determining new structures for silk I and silk II forms, as very recently proposed by Lazo and Downing. ... 

Table 1. Composition of the fibroins of Bombyx mori and Tussah silks ...

The usually known lustre and softness of silk fibres in textile manufacturing does not represent the natural appearance of silk fibres from B. mori cocoons. Untreated fibres reeled from the cocoon form the so-called raw silk. To bring out the smooth and lustrous qualities of silk fabrics, raw silk has to be freed from sericin layers, which surround the fibroin fibres. Depending on the origin, the gum content of silk varies. The content in B. mori cocoons is around 20—30% and therefore relatively high if compared to Tussah silk which is only 5—15% (Gukajani, 1988). 

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