| Abstract: | Silks representative of the three subfamilies of Bombycidae have been studied and it has been found that they all contain cystine residues. The amount present varies, but irrespective of the country of origin is constant for a given species. In all cases the cystine content of the sericin was found to be at least twice that of the fibroin, which suggests that disulphide cross-linking does not contribute to the insolubility of the latter. The cystine content of Bombyx mori fibroin is 10.0 μ mole/g and this work has shown that at least one third of this cystine is present in the sequence Arg-Ala-Leu-Pro-Cys-Asn-Val-Cys Although such a small cystine-containing ring has not previously been reported as occurring in proteins, it is concluded that on stereochemical grounds the structure is sound. |
