Abstract
The effect of copper on the crystal form of silk fibroin crystals (Fcp) treated in the cupriethylenediamine solution (Cu-EDA-1) was studied. The Fcp was obtained by precipitation from the aqueous fibroin solution with chymotrypsin. Another precipitate (Fcplc) was obtained when the Fcp was dissolved in cupri-ethylenediamine solution (Cu-EDA-2) and then dialyzed.
The copper content in the Fcp was confirmed to be very low by atomic absorption analysis (below 0.03mgCu/g fibroin). The X-ray diffraction pattern of the Fcp showed that the Fcp was the β-crystalline form. In the case of Fcplc, the higher pH in the Cu-EDA-2, the more copper was adsorbed in the fibroin. While the amount of copper adsorbed in Fcplc was seriously affected by the copper concentration of the Cu-EDA-2. Fcplc including a large amount of copper (1.5-4.5mgCu/g fibroin) showed the α-crystalline form, while that containing a small amount of copper (below 0.05mgCu/g fibroin) was the, β-one. The results of X-ray diffraction and differential thermal analysis showed that the Fcplc including a large amount of copper has the same structure as the -type fibroin of silk grand
