Morphology and chemical structure of silk

The morphological stmcture of raw silk fibre is given in Fig. 1-10. The actual fibre protein is called fibrion and the protein sericin is the gummy substance that holds the filament together. The average composition of raw silk is 70-75% fihrion (CijHj NjOg), 20-25% sericin, 2-3% waxy substances extractable by ether and alcohol and 1 to 1.7% mineral matter. Sericin is amorphous and dissolves in hot soap solution. Fibrion is the form of a filament thread and dissolves in 5% sodium hydroxide solution at boil. 

Both fibrion and sericin are protein substances built up of 16-18 amino acids, out of which only glycine, alanine, serine and tyrosine make up the largest part of the silk fibre (see Table 1.8) and the remaining amino acids containing bulky side groups are not significant. The chemical stmcture of fibrion and sericin for four 

Amino acids Side groups Sericin (% mol) Fibrion (% mol) 

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