B. mori silkworm

Thermal Properties. Spider dragline silk was thermally stable to about 230°C based on thermal gravimetric analysis (tga) (33). Two thermal transitions were observed by dynamic mechanical analysis (dma), one at —75° C, presumed to represent localized mobiUty in the noncrystalline regions of the silk fiber, and the other at 210°C, indicative of a partial melt or a glass transition. Data from thermal studies on B. mori silkworm cocoon silk indicate a glass-transition temperature, T, of 175°C and stability to around 250°C (37). The T for wild silkworm cocoon silks were slightly higher, from 160 to 210°C. 

Silk fibroin from B. mori silkworm is a fibrous protein whose primary structure largely consists of a repeating sequence of six residues, (Gly-Ala-Gly-Ala-Gly-Ser) [23-27]. Details of the primary structure are described in Ref. [27], Two crystalline forms. Silks I and II, have been reported as the dimorphs of silk fibroin from B. mori in the solid state on the basis of X-ray... 

Cells of the silk gland from B. mori silkworm synthesize an enormous quantity of silk proteins, fibroin and sericin, during a brief period in larval development without cell division. Silk fibroin is exclusively synthesized in the posterior silk gland (each cell produces 10 fibroin molecules, for example, about 80 mg during a period of only 3 to 4 days fifth instar larva)... 

Direct C NMR observations of living B. mori silkworms were applied to the chain dynamics studies of the silk fibroin stored in the silk gland. Figure 9 shows a series of partially relaxed C NMR spectra of the middle silk gland portion of intact mature larva of B. mori. 

The consensus crystalline amino acid repeat in the B. mori silkworm cocoon silk fibroin heavy chain is the 59mer GAGAGSGAAG[SGAGAG]sY. More detailed... 

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