中文摘要：

应用圆二色谱、内源荧光和外源荧光探针研究了丝素蛋白在甲醇-水混合溶剂中的构象变化及机理。结果显示,在浓度低于30%（V/V）的甲醇-水混合溶剂中,处于无规卷曲状态的丝素蛋白可以通过疏水相互作用形成小的疏水区域,随着甲醇浓度的增加,丝素蛋白发生由无规卷曲向β-折叠的构象转变,削弱了疏水侧链的相互作用。分析表明,丝素蛋白的构象变化与溶剂体系的微观结构密切相关,其稳定性主要由肽键单元与混合溶剂中的分子簇之间的相互作用决定。低浓度的甲醇-水混合溶剂保持水固有的氢键结构,对丝素蛋白肽键单元的溶剂化和丝素蛋白构象的影响较小,而随着甲醇浓度的增加,溶剂结构出现由四面体结构的水分子簇向链状结构的甲醇分子簇的转变,丝素蛋白通过形成分子内氢键减少肽键单元与溶剂分子的接触,从而引发丝素蛋白的构象转变。

英文摘要：

A combinational study of circular dichroism,intrinsic fluorescence of protein and exogenous fluorescence probe of ANS was made to investigate the conformational change of silk fibroin in methanol-water mixtures as well as the mechanism.The spectral results showed that small hydrophobic regions were formed in silk fibroin in methanol-water mixtures at the concentration lower than 30%（V/V）via hydrophobic interaction,which was decreased at higher methanol content due to a structural transition of silk fibroin from random coil to β-sheet.The conformational change of silk fibroin was found to be of a close relationship with the microstructure of the solvent and to be determined by the interaction between the peptide unit of silk fibroin and the cluster of the mixed solvent.Methanol-water mixture at low concentration had little effect on the solvation of the peptide unit and the conformation of silk fibroin,as a consequence of the fact that the inherent water structure was conserved.The transition from the tetrahedral-like water structure to the chain-like methanol structure,due to the increasing concentration of methanol,induced the conformational change of silk fibroin to eliminate the contact of peptide unit with the solvent molecular.