Controlling Phase Separation of Lysozyme with Polyvalent Anions
Controlling Phase Separation of Lysozyme with Polyvalent Anions
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DOI：
10.1021/acs.jpcb.8b10868
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发表时间：
2019-01-24
影响因子：
3.3
通讯作者：
Curtis, Robin A.
中科院分区：
文献类型：
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作者：
Bye, Jordan W.;Curtis, Robin A.
通过溶解度和浊度实验、渗透第二维里系数（B-22）测定和溶菌酶溶液的zeta电位值，研究了多价阴离子对蛋白质-蛋白质相互作用和蛋白质净电荷的影响。B-22值表明，所有阴离子都能降低带正电荷的溶菌酶分子之间的蛋白质-蛋白质排斥作用，并且那些净价较高的阴离子更有效。观察到多价阴离子焦磷酸盐和三聚磷酸盐诱导蛋白质重入缩合，这在之前已经在三价阳离子存在下用带负电荷的蛋白质观察到。重入冷凝是一种现象，其中低浓度的多价离子诱导蛋白质沉淀，但进一步增加多价离子浓度导致蛋白质沉淀物再溶解。有趣的是，柠檬酸盐不诱导溶菌酶折返缩合，尽管具有类似的电荷，大小和形状的焦磷酸盐。我们观察到质的差异，蛋白质的行为相比，带负电荷的蛋白质在溶液中的三价阳离子。多磷酸根离子诱导更强的蛋白质-蛋白质吸引力，这与液体-凝胶转变的发生相关，该转变取代了用三价阳离子观察到的液体-液体转变。结果表明，多磷酸盐离子的解决方案提供了一个模型系统，用于探索蛋白质相图和模型相互作用势之间的联系，也突出了离子特异性效应对蛋白质溶解度的重要性。
The ability of polyvalent anions to influence protein-protein interactions and protein net charge was investigated through solubility and turbidity experiments, determination of osmotic second virial coefficients (B-22), and zeta-potential values for lysozyme solutions. B-22 values showed that all anions reduce protein-protein repulsion between positively charged lysozyme molecules, and those anions with higher net valencies are more effective. The polyvalent anions pyrophosphate and tripolyphosphate were observed to induce protein reentrant condensation, which has been previously observed with negatively charged proteins in the presence of trivalent cations. Reentrant condensation is a phenomenon in which low concentrations of polyvalent ions induce protein precipitation, but further increasing polyvalent ion concentration causes the protein precipitate to resolubilize. Interestingly, citrate does not induce lysozyme reentrant condensation despite having a similar charge, size, and shape to pyrophosphate. We observe qualitative differences in protein behavior when compared against negatively charged proteins in solutions of trivalent cations. The polyphosphate ions induce a much stronger protein-protein attraction, which correlates with the occurrence of a liquid-gel transition that replaces the liquid-liquid transition observed with trivalent cations. The results indicate that solutions of polyphosphate ions provide a model system for exploring the link between the protein-phase diagram and model interaction potentials and also highlight the importance that ion-specific effects can have on protein solubility.