Role of Carboxylate Side Chains in the Cation Hofmeister Series
Role of Carboxylate Side Chains in the Cation Hofmeister Series
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DOI：
10.1021/jp212243c
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发表时间：
2012-06-28
影响因子：
3.3
通讯作者：
Cremer, Paul S.
中科院分区：
文献类型：
--
作者：
Kherb, Jaibir;Flores, Sarah C.;Cremer, Paul S.
对含有16个天冬氨酸残基的弹性蛋白样多肽（ELP）进行了热力学和表面特异性光谱研究。目标是探索羧酸根部分在疏水塌陷和相关霍夫迈斯特效应中的作用。用一系列单价和二价金属氯化物盐进行实验。相变温度和光谱数据均表明，二价阳离子与生物聚合物表面的羧酸根有较强的缔合作用，其Kd值在1 ~ 10 mM范围内，缔合顺序为：Zn 2 + > Ca 2 + > Ba 2 + > Sr 2 + > Mg 2 +.单价阳离子显示较弱的结合，其范围从78 mM的NH 4+到345 mM的Cs+。其顺序为：NH ~（4+）> Li ~+ > Na ~+ > NMe ~（4+）> K ~+ > Rb ~+ >= Cs ~+。这些结果与强水合阳离子比弱水合阳离子更紧密地与羧酸根基团结合的概念大体一致。此外，单价系列的数据部分符合匹配水亲和力的规律，虽然Li+和NH 4+不遵循该模型。二价阳离子的系列似乎根本不遵守水亲和力匹配定律。
Thermodynamic and surface-specific spectroscopic investigations were carried with an elastin-like polypeptide (ELP) containing 16 aspartic acid residues. The goal was to explore the role of the carboxylate moieties in hydrophobic collapse and related Hofmeister effects. Experiments were conducted with a series of monovalent and divalent metal chloride salts. Both phase transition temperature and spectroscopic data demonstrated that the divalent cations showed relatively strong association to the carboxylate sites on the biopolymer with K-d values in the range of 1 to 10 mM. The ordering of the divalent series was: Zn2+ > Ca2+ > Ba2+ > Sr2+ > Mg2+. Monovalent cations displayed weaker binding which ranged from 78 mM for NH4+ to 345 mM for Cs+. The order for this series was: NH4+ > Li+ > Na+ > NMe4+ > K+ > Rb+ >= Cs+. These results are in general agreement with the notion that strongly hydrated cations bind more tightly to carboxylate groups than do weakly hydrated cations. Moreover, the data for the monovalent series was partially consistent with the law of matching water affinity, although Li+ and NH4+ did not follow the model. The series for the divalent cations did not appear to obey the law of matching water affinity at all.