We report extended pH- and temperature-induced preparation procedures and explore the materials and molecular properties of different types of hydrogels made from human and bovine serum albumin, the major transport protein in the blood of mammals. We describe the diverse range of properties of these hydrogels at three levels: (1) their viscoelastic (macroscopic) behavior, (2) protein secondary structure changes during the gelation process (via ATR-FTIR spectroscopy), and (3) the hydrogel fatty acid (FA) binding capacity and derive from this the generalized tertiary structure through CW EPR spectroscopy. We describe the possibility of preparing hydrogels from serum albumin under mild conditions such as low temperatures (notably below albumin's denaturation temperature) and neutral pH value. As such, the proteins retain most of their native secondary structure. We find that all the combined data indicate a two-stage gelation process that is studied in detail. We summarize these findings and the explored dependences of the gels on pH, temperature, concentration, and incubation time by proposing phase diagrams for both HSA and BSA gel-states. As such, it has become possible to prepare gels that have the desired nanoscopic and macroscopic properties, which can, in future, be tested for, e.g., drug delivery applications.

中文翻译：

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在宽的pH和温度范围内的血清白蛋白水凝胶：其自组装结构以及纳米和宏观特性的表征†

我们报告了扩展的pH和温度诱导的制备程序，并探索了由人类和牛血清白蛋白（哺乳动物血液中的主要转运蛋白）制成的不同类型水凝胶的材料和分子特性。我们从以下三个方面描述了这些水凝胶的不同性能范围：（1）它们的粘弹性（宏观）行为，（2）凝胶过程中蛋白质二级结构的变化（通过ATR-FTIR光谱）和（3）水凝胶脂肪酸（FA）的结合能力，并通过CW EPR光谱从中得出广义的三级结构。我们描述了在低温（尤其是低于白蛋白的变性温度）和中性pH值等温和条件下从血清白蛋白制备水凝胶的可能性。这样，蛋白质保留了其大部分天然二级结构。我们发现所有合并的数据都表明进行了详细研究的两阶段凝胶化过程。我们通过提出HSA和BSA凝胶态的相图，总结了这些发现以及凝胶对pH，温度，浓度和孵育时间的探索依赖性。因此，制备具有所需纳米和宏观特性的凝胶成为可能，将来可以对其进行测试，例如，药物输送应用。