Complex coacervation of Mg(II) phospho-polymethacrylate, a synthetic analog of sandcastle worm adhesive phosphoproteins,Soft Matter

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Complex coacervation of Mg(II) phospho-polymethacrylate, a synthetic analog of sandcastle worm adhesive phosphoproteins
Soft Matter ( IF 2.9 ) Pub Date : 2017-11-13 00:00:00 , DOI: 10.1039/c7sm01654a
In Taek Song _{1,

2,

3,

4} , Russell J. Stewart _{1,

2,

3,

4}

Affiliation

The highly phosphorylated Pc3 proteins, major components of the sandcastle worm adhesive, are sequestered with Mg as spherical sub-granules within heterogeneous secretory granules in adhesive gland cells. The phase behavior of a synthetic phospho-polymethacrylate analog of the Pc3 phosphoproteins, in the presense of Mg(II), was characterized to determine whether it is chemically possible for the natural adhesive components to be packaged and stored as liquid complex coacervates. Of several multivalent metal salts tested, only MgCl induced complex coacervation of the phospho-copolymer. Complex coacervates formed at Mg/P ratios from 0.5–8, and in [NaCl]s from 0–3 M. At low temperature and pH, the complex coacervates were clear and homogeneous. At higher temperatures and pH, the coacervate phases were translucent. The elastic and viscous moduli initially decreased as temperature increased, but then increased significantly near the temperature boundary between clear and translucent forms. A mechanism is proposed in which relatively weak, ionic strength-independent, outer shell crossbridging of –PO₃²⁻ sidechains by Mg[H₂O]₆²⁺ complex ions is responsible for the clear homogeneous lower viscosity coacervate form. At higher temperature and pH, displacement of inner shell H₂O molecules by phosphate O⁻ ligands creates stronger crossbridges, additional dehydration, and more viscous coacervates. The results demonstrate that Pc3 phosphoproteins can exist as condensed phospho/Mg(II) complex coacervates under conditions expected in the adhesive glands of sandcastle worms in their natural environment. Considering the common regulatory role of phosphorylation and the intracellular abundance of Mg²⁺ it is possible that soft bridging of phosphate groups by Mg[H₂O]_n²⁺ may promote other regulated cellular liquid liquid phase separation phenomena.

中文翻译：

Mg（II）磷酸聚甲基丙烯酸甲酯（沙堡蠕虫粘附磷蛋白的合成类似物）的复杂凝聚

沙堡蠕虫胶粘剂的主要成分，高度磷酸化的Pc3蛋白与Mg隔离，形成胶粘剂腺细胞异质分泌颗粒中的球形亚颗粒Mg。Mg（II）存在下Pc3磷蛋白的合成磷酸-聚甲基丙烯酸酯类似物的相行为）的特性是确定化学上是否有可能将天然胶粘剂成分包装和存储为液体复合凝聚层。在测试的几种多价金属盐中，只有MgCl引起磷酸共聚物的复合凝聚。Mg / P比为0.5–8，[NaCl] s为0–3 M时，形成了复杂的凝聚层。在低温和pH值下，复杂的凝聚层是透明且均匀的。在较高的温度和pH下，凝聚层是半透明的。弹性模量和粘性模量最初随着温度的升高而降低，但随后在透明和半透明形式之间的温度边界附近显着升高。提出了一种机制，其中–PO ₃^2-的相对弱，不依赖离子强度的外壳交叉桥化Mg [H ₂ O] ₆²⁺络合物离子形成的侧链负责形成透明的均质低粘度凝聚层形式。在较高的温度和pH值，内壳H的位移₂通过磷酸○○分子^-配体创建更强crossbridges，附加脱水，并更粘稠凝聚。结果表明，Pc3磷蛋白可以在沙堡蠕虫的黏附腺在其自然环境中预期的条件下，以缩合的磷酸/ Mg（II）凝聚层的形式存在。考虑到磷酸化和Mg ²⁺的细胞内丰度的共同调节作用，Mg [H ₂O] _n²⁺可能会促进其他调控的细胞液相分离现象。

更新日期：2017-11-17

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