Structural characterization and artificial fiber formation of Bombyx mori silk fibroin in hexafluoro-iso-propanol solvent system

High-resolution solution C-13-NMR and CD studies of Bombyx mori silk fibroin revealed the presence of an ordered secondary structure 3(10)-helix, in hexafluoro-iso-propanol (HFIP). The, solid-state structure of the silk fibroin film prepared by drying it gently from the HFIP solution still keep the structure, 3(10)-helix, which was studied with high-resolution solid State C-13-NMR. The structural transition from the 3(10)-helix to silk II structure, heterogeneous structure including antiparallel beta-sheet, occurred during the artificial spinning from the HFIP solution. The wide-angle x-ray diffraction and differential scanning calorimetry thermograms of the artificial spinning fiber after postspinning treatments were observed together with the stress-strain curves. The results emphasize that the molecular structures, controlled morphology, and mechanical properties of the protein-based synthetic polymers can be modulated for enhancing biocompatibility. (C) 2003 Wiley, Periodicals, Inc.