title: Conformational transition and liquid crystalline state of regenerated silk fibroin in water.
abstract: The conformational transition of molecular chains of regenerated silk fibroin (SF) aqueous solution is systematically investigated by circular dichroism, Raman, IR, and UV-vis spectroscopies. It is found that an initial random coil conformation of the SF can be readily changed into an ordered beta-sheet structure by optimizing the solution conditions, such as the SF concentration, pH, temperature, or metal-ion content. Circular dichroic spectra quantitatively confirm a steadily decreased content of the random coil conformation but a significantly increased beta-sheet content after an ultrasonic or extruding treatment. Furthermore, the extrusion is more powerful to achieve high beta-sheet content than the ultrasonic. It is interesting that the polarized optical micrographs of the SF aqueous solution extruded by injection illustrate the formation and existence of liquid crystalline state. A study of extrusion in vitro could be used as a model system to understand the natural silk spinning process in silkworm.
authors: Institute of Materials Chemistry, Key Laboratory of Advanced Civil Engineering Materials, College of Materials Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China. adamxgli@yahoo.com
authors: Xin-Gui
authors: XG
authors: Li
authors: Li-Ya
authors: LY
authors: Wu
authors: Mei-Rong
authors: MR
authors: Huang
authors: Hui-Li
authors: HL
authors: Shao
authors: Xue-Chao
authors: XC
authors: Hu
mesh_terms: D000818:Animals; D012831:Bombyx / Q000737:chemistry* / Q000378:metabolism; D005349:Fibroins / Q000737:chemistry* / Q000378:metabolism; D006358:Hot Temperature; D019476:Insect Proteins / Q000737:chemistry* / Q000378:metabolism; D007477:Ions / Q000737:chemistry / Q000378:metabolism; D050866:Liquid Crystals; D008670:Metals / Q000737:chemistry / Q000378:metabolism; D008956:Models, Chemical; D017433:Protein Structure, Secondary / Q000502:physiology; D013057:Spectrum Analysis; D014867:Water / Q000737:chemistry / Q000378:metabolism
chemical_list: D019476:Insect Proteins; D007477:Ions; D008670:Metals; C482288:fibroin, silkworm; D014867:Water; D005349:Fibroins