Keratin molecules contain many hydrophobic amino acids and disulfide bonds that render them poorly soluble in water, thus greatly limiting their properties and applications as biomaterials. Improving the solubility of keratin and the stability of highly concentrated solutions is the key to solving this. In this paper, wool keratin was first dissolved and then PEGylated in a novel reduced deep eutectic solvent (DES) to obtain a stable keratin solution with a concentration of 300 g/L. The hydrophobicity, particle size distribution, conformation, and rheological properties of this high-concentration keratin solution were investigated. The results showed that a thiol–ene click reaction reduced the thiol content by up to 60% and inhibited thiol–thiol cross-linking. PEGylation also reduced the hydrophobic areas on the keratin surface, thus improving its stability in an aqueous solution. In the highly concentrated PEGylated keratin solution, the secondary conformation changed from α-helix to β-sheet. Polarized light microscopy indicated the formation of liquid crystals after applying friction. Rheological tests showed that the solution had a shear-thinning behavior at high shear rates, indicating that molecular chain reorientation was induced under the action of shear forces, which may help to strengthen the materials.

中文翻译：

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在低共熔溶剂中通过聚乙二醇化制备稳定的高浓度角蛋白溶液

角蛋白分子含有许多疏水性氨基酸和二硫键，使其难溶于水，从而极大地限制了其作为生物材料的性能和应用。提高角蛋白的溶解度和高浓度溶液的稳定性是解决这一问题的关键。本文首先将羊毛角蛋白溶解，然后在新型还原低共熔溶剂（DES）中进行聚乙二醇化，以获得浓度为300 g/L的稳定角蛋白溶液。研究了这种高浓度角蛋白溶液的疏水性、粒径分布、构象和流变特性。结果表明，硫醇-烯点击反应可将硫醇含量降低高达 60%，并抑制硫醇-硫醇交联。聚乙二醇化还减少了角蛋白表面的疏水区域，从而提高了其在水溶液中的稳定性。在高浓度的聚乙二醇化角蛋白溶液中，二级构象从α-螺旋变为β-折叠。偏光显微镜表明施加摩擦后形成了液晶。流变测试表明，该溶液在高剪切速率下具有剪切稀化行为，表明在剪切力的作用下引起分子链重新取向，这可能有助于增强材料。