Polyamine/Nucleotide Coacervates Provide Strong Compartmentalization of Mg2+, Nucleotides, and RNA

被引:125
作者
Frankel, Erica A. [1 ,2 ]
Bevilacqua, Philip C. [1 ,2 ,3 ]
Keating, Christine D. [1 ]
机构
[1] Penn State Univ, Dept Chem, University Pk, PA 16802 USA
[2] Penn State Univ, Ctr RNA Mol Biol, University Pk, PA 16802 USA
[3] Penn State Univ, Dept Biochem & Mol Biol, University Pk, PA 16802 USA
关键词
POLYELECTROLYTE MOLECULAR-WEIGHT; COMPLEX COACERVATION; ADENOSINE-TRIPHOSPHATE; PHASE-SEPARATION; PROTOCELL MODEL; 2-PHASE SYSTEM; P RNA; DROPLETS; BEHAVIOR; POLY(ALLYLAMINE);
D O I
10.1021/acs.langmuir.5b04462
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Phase separation of aqueous solutions containing polyelectrolytes can lead to formation of dense, solute-rich liquid droplets referred to as coacervates, surrounded by a dilute continuous phase of much larger volume. This type of liquid liquid phase separation is thought to help explain the appearance of polyelectrolyte-rich intracellular droplets in the cytoplasm and nucleoplasm of extant biological cells and may be relevant to protocellular compartmentalization of nucleic acids on the early Earth. Here we describe complex coacervates formed upon mixing the polycation poly(allylamine) (PAH, 15 kDa) with the anionic nucleotides adenosine 5'-mono-, di-, and triphosphate (AMP, ADP, and ATP). Droplet formation was observed over a wide range of pH and MgCl2 concentrations. The nucleotides themselves as well as Mer and RNA oligonucleotides were all extremely concentrated within the coacervates. Nucleotides present at just 2.5 mM in bulk solution had concentrations greater than 1 M inside the coacervate droplets. A solution with a total Mg2+ concentration of 10 mM had 1-5 M Mg2+ in the coacervates, and RNA random sequence (N-54) partitioned 40 000-fold into the coacervates. Coacervate droplets are thus rich in nucleotides, Mg2+, and RNA, providing a medium favorable for generating functional RNAs. Compartmentalization of nucleotides at high concentrations could have facilitated their polymerization to form oligonucleotides, which preferentially accumulate in the droplets. Locally high Mg2+ concentrations could have aided folding and catalysis in an RNA world, making coacervate droplets an appealing platform for exploring protocellular environments.
引用
收藏
页码:2041 / 2049
页数:9
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