Effects of Hofmeister anions on the phase transition temperature of elastin-like polypeptides.
Effects of Hofmeister anions on the phase transition temperature of elastin-like polypeptides.
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DOI：
10.1021/jp8062977
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发表时间：
2008-11-06
期刊：
影响因子：
--
通讯作者：
Cremer PS
中科院分区：
文献类型：
--
作者：
Cho Y;Zhang Y;Christensen T;Sagle LB;Chilkoti A;Cremer PS
研究了Hofmeister系列的11种钠盐对两种弹性蛋白样多肽(ELP)的低临界溶解温度(LCST)的调节作用。结果发现，这些ELP的疏水塌陷/聚集一般遵循该系列。具体地说，亲水性阴离子通过极化ELP上水合的酰胺基团中的界面水分子来降低LCST。另一方面，杂化阴离子通过表面张力效应降低了LcST。此外，杂化阴离子在低盐浓度下表现出盐渍特性，这与阴离子与生物聚合物的饱和结合有关。这些总体机理效应与以前发现的聚N-异丙基丙烯酰胺(PNIPAM)疏水塌陷和聚集的机理相似。然而，PNIPAM和ELP之间有一个关键的区别。也就是说，在足够浓度的粘性盐存在下，PNIPAM经历了一个随温度变化的两步崩塌过程。相比之下，在本文研究的所有情况下，ELP都会在一个步骤中崩溃。这表明，在高度耦合的过程中，从酰胺部分周围的水分子的去除触发了疏水水合水的去除。这两个ELP的LCST行为也有一些关键差异。具体地说，与疏水性较强的ELP V5-120相比，亲水性较强的ELP V5A2G3-120结构表现出塌陷/聚集行为，这与分配到聚合物/水界面的更高浓度的阴离子一致。研究还发现，与ELP V5-120相比，较大的阴离子更容易与ELP V5A2G3-120结合。后者的结果是根据阴离子对ELP的相对结合位置可及性来解释的。
The modulation of the lower critical solution temperature (LCST) of two elastin-like polypeptides (ELPs) was investigated in the presence of 11 sodium salts that span the Hofmeister series for anions. It was found that the hydrophobic collapse/aggregation of these ELPs generally followed the series. Specifically, kosmotropic anions decreased the LCST by polarizing interfacial water molecules involved in hydrating amide groups on the ELPs. On the other hand, chaotropic anions lowered the LCST through a surface tension effect. Additionally, chaotropic anions showed salting-in properties at low salt concentrations that were related to the saturation binding of anions with the biopolymers. These overall mechanistic effects were similar to those previously found for the hydrophobic collapse and aggregation of poly(N-isopropylacrylamide), PNIPAM. There is, however, a crucial difference between PNIPAM and ELPs. Namely, PNIPAM undergoes a two-step collapse process as a function of temperature in the presence of sufficient concentrations of kosmotropic salts. By contrast, ELPs undergo collapse in a single step in all cases studied herein. This suggests that the removal of water molecules from around the amide moieties triggers the removal of hydrophobic hydration waters in a highly coupled process. There are also some key differences between the LCST behavior of the two ELPs. Specifically, the more hydrophilic ELP V5A2G3-120 construct displays collapse/aggregation behavior that is consistent with a higher concentration of anions partitioning to polymer/aqueous interface as compared to the more hydrophobic ELP V5-120. It was also found that larger anions could bind with ELP V5A2G3-120 more readily in comparison with ELP V5-120. These latter results were interpreted in terms of relative binding site accessibility of the anion for the ELP.
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