The fibroin was suspended following the method of Yamaguchi et al. (1989). Briefly posterior silk gland and shredded
cocoon fiber was discriminated by the method described by Rajan et al. (1992), dissolved in 60 per cent lithium
thiocyanate (LiSCN) solution and incubated overnight at 4oC with gentle stirring. The soluble protein was collected
and dialyzed against Tris-HCl buffer (Tris 20 m M, pH 8.0). After sericin was dissolved in 0.025 N NaOH, the left-over
silk fiber was treated with 0.1 N NaOH solutions for 24 hours at 4oC with constant stirring. The solution was
extensively dialyzed against double distilled water for 2-3 days. The dialyzed sample was centrifuged at 8000 rpm; the
supernatant was concentrated and stored at -20oC in aliquots.