Charges and their contribution to protein–protein interactions are essential for the key structural and dynamic properties of monoclonal antibody (mAb) solutions. In fact, they influence the apparent molecular weight, the static structure factor, the collective diffusion coefficient, or the relative viscosity, and their concentration dependence. Further, charges play an important role in the colloidal stability of mAbs. There exist standard experimental tools to characterize mAb net charges, such as the measurement of the electrophoretic mobility, the second virial coefficient, or the diffusion interaction parameter. However, the resulting values are difficult to directly relate to the actual overall net charge of the antibody and to theoretical predictions based on its known molecular structure. Here, we report the results of a systematic investigation of the solution properties of a charged IgG1 mAb as a function of concentration and ionic strength using a combination of electrophoretic measurements, static and dynamic light scattering, small-angle X-ray scattering, and tracer particle-based microrheology. We analyze and interpret the experimental results using established colloid theory and coarse-grained computer simulations. We discuss the potential and limits of colloidal models for the description of the interaction effects of charged mAbs, in particular pointing out the importance of incorporating shape and charge anisotropy when attempting to predict structural and dynamic solution properties at high concentrations.

中文翻译：

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结合散射实验和胶体理论来表征浓抗体溶液中的电荷效应

电荷及其对蛋白质-蛋白质相互作用的贡献对于单克隆抗体 (mAb) 溶液的关键结构和动态特性至关重要。事实上，它们影响表观分子量、静态结构因子、集体扩散系数或相对粘度及其浓度依赖性。此外，电荷在单克隆抗体的胶体稳定性中起着重要作用。存在表征 mAb 净电荷的标准实验工具，例如电泳迁移率、第二维里系数或扩散相互作用参数的测量。然而，所得值很难直接与抗体的实际总净电荷以及基于其已知分子结构的理论预测相关。在此，我们报告了结合电泳测量、静态和动态光散射、小角 X 射线散射和示踪剂对带电 IgG1 mAb 的溶液特性作为浓度和离子强度函数进行系统研究的结果基于颗粒的微观流变学。我们使用已建立的胶体理论和粗粒度计算机模拟来分析和解释实验结果。我们讨论了胶体模型在描述带电单克隆抗体相互作用效应方面的潜力和局限性，特别指出了在尝试预测高浓度的结构和动态溶液特性时结合形状和电荷各向异性的重要性。