Analiza, Inc., 3516 Superior Ave., Suite 4407B, Cleveland, OH, USA.
Analiza, Inc., 3516 Superior Ave., Suite 4407B, Cleveland, OH, USA.
Int J Biol Macromol. 2018 Oct 1;117:1224-1251. doi: 10.1016/j.ijbiomac.2018.06.030. Epub 2018 Jun 14.
Water represents a common denominator for liquid-liquid phase transitions leading to the formation of the polymer-based aqueous two-phase systems (ATPSs) and a set of the proteinaceous membrane-less organelles (PMLOs). ATPSs have a broad range of biotechnological applications, whereas PMLOs play a number of crucial roles in cellular compartmentalization and often represent a cellular response to the stress. Since ATPSs and PMLOs contain high concentrations of polymers (such as polyethylene glycol (PEG), polypropylene glycol (PPG), Ucon, and polyvinylpyrrolidone (PVP), Dextran, or Ficoll) or biopolymers (peptides, proteins and nucleic acids), it is expected that the separated phases of these systems are characterized by the noticeable changes in the solvent properties of water. These changes in solvent properties can drive partitioning of various compounds (proteins, nucleic acids, organic low-molecular weight molecules, metal ions, etc.) between the phases of ATPSs or between the PMLOs and their surroundings. Although there is a sizable literature on the properties of the ATPS phases, much less is currently known about PMLOs. In this perspective article, we first represent liquid-liquid phase transitions in water, discuss different types of biphasic (or multiphasic) systems in water, and introduce various PMLOs and some of their properties. Then, some basic characteristics of polymer-based ATPSs are presented, with the major focus being on the current understanding of various properties of ATPS phases and solvent properties of water inside them. Finally, similarities and differences between the polymer-based ATPSs and biological PMLOs are discussed.
水代表了导致形成基于聚合物的双水相体系（ATPS）和一系列蛋白质无膜细胞器（PMLO）的液相-液相转变的共同基础。ATPS 具有广泛的生物技术应用，而 PMLO 在细胞区室化中发挥着多种关键作用，并且通常代表细胞对压力的反应。由于 ATPS 和 PMLO 含有高浓度的聚合物（如聚乙二醇（PEG）、聚丙二醇（PPG）、Ucon 和聚乙烯吡咯烷酮（PVP）、葡聚糖或 Ficoll）或生物聚合物（肽、蛋白质和核酸），预计这些系统的分离相具有水的溶剂性质的显著变化。这些溶剂性质的变化可以驱动各种化合物（蛋白质、核酸、有机低分子量分子、金属离子等）在 ATPS 相之间或在 PMLO 与其周围环境之间的分配。尽管有大量关于 ATPS 相性质的文献，但目前对 PMLO 的了解要少得多。在这篇观点文章中，我们首先介绍水的液-液相转变，讨论水中不同类型的双相（或多相）系统，并介绍各种 PMLO 及其一些性质。然后，介绍了基于聚合物的 ATPS 的一些基本特征，主要重点是目前对 ATPS 相的各种性质和其中水的溶剂性质的理解。最后，讨论了基于聚合物的 ATPS 和生物 PMLO 之间的相似之处和差异。
