Laboratory of Physics and Physical Chemistry of Foods, Wageningen University, Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands.
Molecules. 2021 Mar 11;26(6):1543. doi: 10.3390/molecules26061543.
The ability to separate enzymes, nucleic acids, cells, and viruses is an important asset in life sciences. This can be realised by using their spontaneous asymmetric partitioning over two macromolecular aqueous phases in equilibrium with one another. Such phases can already form while mixing two different types of macromolecules in water. We investigate the effect of polydispersity of the macromolecules on the two-phase formation. We study theoretically the phase behavior of a model polydisperse system: an asymmetric binary mixture of hard spheres, of which the smaller component is monodisperse and the larger component is polydisperse. The interactions are modelled in terms of the second virial coefficient and are assumed to be additive hard sphere interactions. The polydisperse component is subdivided into sub-components and has an average size ten times the size of the monodisperse component. We calculate the theoretical liquid-liquid phase separation boundary (the binodal), the critical point, and the spinodal. We vary the distribution of the polydisperse component in terms of skewness, modality, polydispersity, and number of sub-components. We compare the phase behavior of the polydisperse mixtures with their concomittant monodisperse mixtures. We find that the largest species in the larger (polydisperse) component causes the largest shift in the position of the phase boundary, critical point, and spinodal compared to the binary monodisperse binary mixtures. The polydisperse component also shows fractionation. The smaller species of the polydisperse component favor the phase enriched in the smaller component. This phase also has a higher-volume fraction compared to the monodisperse mixture.
分离酶、核酸、细胞和病毒的能力是生命科学的重要资产。这可以通过利用它们在与彼此平衡的两种大分子水溶液之间自发的不对称分配来实现。在将两种不同类型的大分子混合在水中时，就可以形成这样的相。我们研究了大分子的多分散性对两相形成的影响。我们从理论上研究了模型多分散系统的相行为：硬球的不对称二元混合物，其中较小的组分是单分散的，较大的组分是多分散的。相互作用用第二维里系数来建模，并假定为加和硬球相互作用。多分散组分被细分为子组分，平均大小是单分散组分的十倍。我们计算了理论的液-液相分离边界（分相线）、临界点和旋节线。我们根据偏度、模态、多分散性和子组分的数量来改变多分散组分的分布。我们比较了多分散混合物与相应的单分散混合物的相行为。我们发现，较大组分中的最大物种与二元单分散混合物相比，对相边界、临界点和旋节线的位置产生了最大的偏移。多分散组分也显示出分馏现象。多分散组分中的较小物种有利于富含较小组分的相。与单分散混合物相比，该相的体积分数也更高。
