Figure 3
Comparison of the solubilisation capabilities of 5 different experimental salt solutions using modern silk samples derived from 7 different silk moth species. (a) Summary of the conditions required for solubilisation (sol.) (and whether achieved or not), including temperature (temp.) and time in minutes (min.) as determined but the disappearance into solution of the solid silk sample. *Wild silk samples showed no evidence of solubilisation at 40°, 60°, or 80 °C for ~ 180 min. (b) Xanthoproteic reaction of silk fibroin (S. ricini) solution by formic acid: 0.5 mg fibers in each tube with (1) 500 μl of 7 M Ca(NO3)2, (2) 500 μl 7 M Ca(NO3)2 + 0.1% FA on the weight of fabric, (3) 1 ml 7 M Ca(NO3)2, and (4) 1 ml 7 M Ca(NO3)2 + 0.1% FA. Formic acid was added after solubilisation occurred in the salt solution at 130 °C for 10 min. (c) 7 M Ca(NO3)2 fibroin solutions of B. mori, B. mandarina, A. pernyi, A. mylitta, A. yamamai, A. assamensis, and S. ricini after xanthoproteic reaction. Color intensity results from the presence of aromatic residues. This figure in this research was created by the first author using photographs of experimental processes edited with Adobe Photoshop CS6.
