Macromolecular Crowding Modifies the Impact of Specific Hofmeister Ions on the Coil-Globule Transition of PNIPAM
Macromolecular Crowding Modifies the Impact of Specific Hofmeister Ions on the Coil-Globule Transition of PNIPAM
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DOI：
10.1021/acs.jpcb.5b01255
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发表时间：
2015-08-13
影响因子：
3.3
通讯作者：
Sekiya, Hiroshi
中科院分区：
文献类型：
--
作者：
Sakota, Kenji;Tabata, Daiki;Sekiya, Hiroshi
大分子拥挤改变了许多生物过程，从体内蛋白质折叠和酶反应到体外蛋白质的沉淀和结晶。在此，我们已经研究了特定的单价Hofmeister盐（NaH 2 PO 4，NaF，NaCl，NaClO 4，NaSCN）的聚（N-异丙基丙烯酰胺）（PNIPAM）的线圈-小球转变在拥挤的大分子环境中的效果作为一个模型，用于理解特定的离子效应在拥挤的大分子环境中的蛋白质的溶解度和稳定性。结果发现，虽然盐（NaH 2 PO 4，NaF，和NaCl）和大分子拥挤（聚乙二醇）几乎独立地降低了转变温度，大分子拥挤的情况下的离液剂（NaClO 4和NaSCN）的转变温度有很大的影响。PNIPAM上吸附的离液阴离子（ClO 4-或SCN-）之间的静电排斥可能会降低与排斥体积效应相关的水的熵增益，导致转变温度的升高，特别是在拥挤的环境中。此外，在拥挤的环境中，离液阴离子对PNIPAM的亲和力变小，导致转变温度的进一步修改。因此，我们已经发现，大分子拥挤改变了特定的Hofmeister离子的影响上的线圈小球过渡的PNIPAM。
Macromolecular crowding alters many biological processes ranging from protein folding and enzyme reactions in vivo to the precipitation and crystallization of proteins in vitro. Herein, we have investigated the effect of specific monovalent Hofmeister salts (NaH2PO4, NaF, NaCl, NaClO4, and NaSCN) on the coil-globule transition of poly(N-isopropylacrylamide) (PNIPAM) in a crowded macromolecular environment as a model for understanding the specific-ion effect on the solubility and stability of proteins in a crowded macromolecular environment. It was found that although the salts (NaH2PO4, NaF, and NaCl) and the macromolecular crowder (polyethylene glycol) lowered the transition temperature almost independently, the macromolecular crowder had a great impact on the transition temperature in the case of the chaotropes (NaClO4 and NaSCN). The electrostatic repulsion between the chaotropic anions (ClO4- or SCN-) adsorbed on PNIPAM may reduce the entropic gain of water associated with the excluded volume effect, leading to an increase in the transition temperature, especially in the crowded environment. Furthermore, the affinity of the chaotropic anions for PNIPAM becomes small in the crowded environment, leading to further modification of the transition temperature. Thus, we have revealed that macromolecular crowding alters the effect of specific Hofmeister ions on the coil-globule transition of PNIPAM.