title: Optical spectroscopy to investigate the structure of regenerated Bombyx mori silk fibroin in solution.
abstract: Fluorescence and circular dichroism spectroscopy were used to monitor the conformational transition of regenerated Bombyx mori silk fibroin (RSF) in aqueous solutions under different conditions. According to the analysis of fluorescence spectra using anilinonaphthalene-8-sulfonic acid magnesium salt (ANS) as an external probe, the destruction of the hydrophobic core prior to the secondary structure change suggests that this collapse may initiate the conformational transition from random coil to beta-sheet for RSF. The temperature dependence of the structural changes of RSF, detected by both fluorescence spectroscopy and circular dichroism, shows a reversible process upon heating and recooling, with the midpoint around 45 degrees C. The results also indicate that most of the tryptophan (Trp) residues contained in silk fibroin are concentrated on the surface of the unfolded protein. However, they will change their location in the highly ordered structure (e.g., becoming more homogeneous) with the conformational transition of silk fibroin. Moreover, our studies also suggest that the presence of water plays a crucial role during the structure changes of fibroin.
authors.affiliation: Department of Macromolecular Science, Fudan University, Shanghai 200433, People's Republic of China.
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Yang
authors.forename: Zhengzhong
authors.initials: Z
authors.lastname: Shao
authors.forename: Xin
authors.initials: X
authors.lastname: Chen
authors.forename: Ping
authors.initials: P
authors.lastname: Zhou
mesh_terms: D000817:Anilino Naphthalenesulfonates / Q000737:chemistry; D000818:Animals; D012831:Bombyx / Q000737:chemistry*; D002942:Circular Dichroism; D005349:Fibroins / Q000737:chemistry*; D011487:Protein Conformation; D012996:Solutions; D013050:Spectrometry, Fluorescence; D013057:Spectrum Analysis / Q000379:methods*; D013696:Temperature; D014364:Tryptophan / Q000737:chemistry
chemical_list: D000817:Anilino Naphthalenesulfonates; D012996:Solutions; C027132:1-anilino-8-naphthalenesulfonate; D014364:Tryptophan; D005349:Fibroins