Institute of Particle Technology, Interdisciplinary Center for Functional Particle Systems, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
Institute of Human Nutrition and Food Science, Division of Food Technology, Kiel University, 24118, Kiel, Germany.
Eur Biophys J. 2020 Dec;49(8):745-760. doi: 10.1007/s00249-020-01421-4. Epub 2020 Jan 31.
The whey protein beta-lactoglobulin is the building block of amyloid fibrils which exhibit a great potential in various applications. These include stabilization of gels or emulsions. During biotechnological processing, high shear forces lead to fragmentation of fibrils and therefore to smaller fibril lengths. To provide insight into such processes, pure straight amyloid fibril dispersions (prepared at pH 2) were produced and sheared using the rotor stator setup of an Ultra Turrax. In the first part of this work, the sedimentation properties of fragmented amyloid fibrils sheared at different stress levels were analyzed with mulitwavelength analytical ultracentrifugation (AUC). Sedimentation data analysis was carried out with the boundary condition that fragmented fibrils were of cylindrical shape, for which frictional properties are known. These results were compared with complementary atomic force microscopy (AFM) measurements. We demonstrate how the sedimentation coefficient distribution from AUC experiments is influenced by the underlying length and diameter distribution of amyloid fibrils.In the second part of this work, we show how to correlate the fibril size reduction kinetics with the applied rotor revolution and the resulting energy density, respectively, using modal values of the sedimentation coefficients obtained from AUC. Remarkably, the determined scaling laws for the size reduction are in agreement with the results for other material systems, such as emulsification processes or the size reduction of graphene oxide sheets.
乳清蛋白β-乳球蛋白是淀粉样纤维的构建块，在各种应用中具有很大的潜力。这些应用包括凝胶或乳液的稳定化。在生物技术加工过程中，高剪切力会导致纤维的断裂，从而导致纤维长度减小。为了深入了解这些过程，我们使用 Ultra Turrax 的转子定子装置制备了纯直的淀粉样纤维分散体（在 pH 2 下制备）并进行了剪切。在这项工作的第一部分中，使用多角度分析超速离心（AUC）分析了在不同应力水平下剪切的碎片化淀粉样纤维的沉降特性。沉降数据分析采用的边界条件是碎片化纤维为圆柱形，其摩擦特性是已知的。这些结果与原子力显微镜（AFM）测量结果进行了比较。我们展示了 AUC 实验中的沉降系数分布如何受到淀粉样纤维的长度和直径分布的影响。在这项工作的第二部分中，我们展示了如何使用 AUC 获得的沉降系数模态值，将纤维尺寸减小的动力学与所施加的转子转速和相应的能量密度相关联。值得注意的是，确定的尺寸减小的比例定律与其他材料体系（如乳化过程或氧化石墨烯片的尺寸减小）的结果一致。
