Bai Qingwen, Zhang Qiufen, Jing Hairong, Chen Jiaxin, Liang Dehai
Beijing National Laboratory for Molecular Sciences, Department of Polymer Science and Engineering and the Key Laboratory of Polymer Chemistry and Physics of the Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China.
J Phys Chem B. 2021 Jan 14;125(1):49-57. doi: 10.1021/acs.jpcb.0c09225. Epub 2020 Dec 29.
The membraneless organelles (MLOs) and coacervates of oppositely charged polyelectrolytes are both formed by liquid-liquid phase separation. To reveal how the crowded cell interior regulates the MLOs, we chose the coacervates formed by peptide S5 and single-stranded oligonucleotide (ss-oligo) at 1:1 charge ratio and investigated the phase separation processes in polyacrylamide (PAM) and poly(ethylene oxide) (PEO) media at varying concentrations. Results show that the droplet formation unit is the neutral primary complex, instead of individual S5 or ss-oligo. Therefore, the coacervation process can be described by the classic theory of nucleation and growth. The dynamic scaling relationships show that S5/ss-oligo coacervation undergoes in sequence the heterogeneous nucleation, diffusion-limited growth, and Brownian motion coalescence with time. The inert crowders generate multiple effects, including accelerating the growth of droplets, weakening the electrostatic attraction, and slowing down or even trapping the droplets in the crowder network. The overall effect is that both the size and size distribution of the droplets decrease with increasing crowder concentration, and the effect of PEO is stronger than that of PAM. Our study provides a further step toward a deeper understanding of the kinetics of MLOs in crowded living cells.
无膜细胞器（MLOs）和带相反电荷的聚电解质凝聚物均由液-液相分离形成。为了揭示拥挤的细胞内环境如何调节MLOs，我们选择了由肽S5和单链寡核苷酸（ss-oligo）以1:1电荷比形成的凝聚物，并研究了在不同浓度的聚丙烯酰胺（PAM）和聚环氧乙烷（PEO）介质中的相分离过程。结果表明，液滴形成单元是中性初级复合物，而不是单个的S5或ss-oligo。因此，凝聚过程可以用经典的成核和生长理论来描述。动态标度关系表明，S5/ss-oligo凝聚随时间依次经历异质成核、扩散限制生长和布朗运动聚并。惰性拥挤剂产生多种效应，包括加速液滴生长、减弱静电吸引力以及使液滴在拥挤剂网络中减速甚至捕获。总体效果是，随着拥挤剂浓度的增加，液滴的尺寸和尺寸分布均减小，且PEO的效果强于PAM。我们的研究朝着更深入理解拥挤活细胞中MLOs的动力学又迈进了一步。
