CHARACTERIZATION OF WATERS OF HYDROPHOBIC HYDRATION BY MICROWAVE DIELECTRIC RELAXATION
CHARACTERIZATION OF WATERS OF HYDROPHOBIC HYDRATION BY MICROWAVE DIELECTRIC RELAXATION
复制标题
通过微波介电弛豫表征疏水水合水
DOI：
10.1021/ja962374r
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发表时间：
1997
影响因子：
15
通讯作者：
D. McPherson
中科院分区：
文献类型：
--
作者：
D. Urry;S. Peng;Jie Xu;D. McPherson
在本文中，在疏水弹性蛋白质基聚合物，如（GVGVP）251和（GVGIP）260的水溶液中观察到的温度依赖性介电弛豫接近5 GHz（在一个频率低于散装水）。在溶液的低温下稀释时，随着疏水性从具有侧链-CH（CH 3）2的瓦尔（V）增加到添加CH 2部分（即-CH（CH 3）CH 2CH 3）的Ile（I），这种弛豫变得更强烈，接近不同的疏水性依赖性极限。随着基于弹性蛋白质的聚合物的溶液的温度从低于它们各自的疏水折叠和组装的逆温度转变升高到高于它们各自的逆温度转变，松弛强度降低到接近0。此外，使用聚合物（GEGXP GVGVP GVGVP GVGVP GVGXP）n其中两个X残基是两个V或两个Phe（F）残基，具有-CH 2C 6 H5的芳族苯基侧链，谷氨酸（E）侧链的电离（即，从COOH形成COO-）以电荷密度依赖的方式破坏疏水水合的大部分沃茨，先前在晶体结构中观察到的排列沃茨水1，2与疏水性部分相邻。本文的特点，第一次，沃茨的疏水水化（NHH）的稀释度，温度和聚合物电荷密度的变量。在没有电荷的情况下，Nhh似乎比五边形排列的沃茨的第一层壳更广泛。这种表征的重要性在于人们普遍认为疏水水合的沃茨的热力学对蛋白质和蛋白质基聚合物的疏水折叠和功能至关重要。3-7先前的介电弛豫研究延伸到微波（超千兆赫）范围内，已经报道了蛋白质，如肌红蛋白，8，9溶菌酶，10和胶原蛋白，11和钙。10 GHz弛豫确实被认为是由蛋白质水合作用引起的。然而，由于几个原因，以前的蛋白质研究无法与疏水性水合相关的任何部分的松弛归因于蛋白质水合。首先，只有很小一部分的水化作用
In the present paper, a temperature dependent dielectric relaxation near 5 GHz (at a frequency just lower than that of bulk water) is observed in aqueous solutions of hydrophobic elastic protein-based polymers, such as (GVGVP) 251 and (GVGIP) 260. On dilution at low temperatures of the solution, this relaxation becomes more intense approaching different hydrophobicity dependent limits as the hydrophobicity increases from Val (V) with the side chain-CH (CH3) 2 to Ile (I) with the addition of a CH2 moiety (ie,-CH (CH3) CH2CH3). The relaxation decreases in intensity to near 0 as the temperature of solutions of the elastic protein-based polymers are raised from below to above their respective inverse temperature transitions of hydrophobic folding and assembly. Furthermore, using the polymers (GEGXP GVGVP GVGVP GVGVP GVGVP GVGXP) n where the two X residues are either two V or two Phe (F) residues with the aromatic phenyl side chain of-CH2C6H5, ionization of glutamic acid (E) side chains (ie, the formation of COO-from COOH) destroys the majority of the waters of hydrophobic hydration in a charge density dependent manner down to a limit suggestive of remaining pentagonally arranged waters previously observed in crystal structures1, 2 adjacent to hydrophobic moieties. This paper characterizes, for the first time, waters of hydrophobic hydration (Nhh) in terms of the variables of dilution, temperature and polymer charge density. In the absence of charge, Nhh appears to be more extensive than the first shell of pentagonally arranged waters. The significance of this characterization resides in the widely held view that the thermodynamics of waters of hydrophobic hydration is central to the hydrophobic folding and function of proteins and proteinbased polymers. 3-7Previous dielectric relaxation studies extending into the microwave (supra gigahertz) range have been reported on proteins such as myoglobin, 8, 9 lysozyme, 10 and collagen, 11 and the ca. 10 GHz relaxation was, indeed, recognized as arising from protein hydration. For several reasons, however, the previous protein studies were unable to correlate with hydrophobic hydration any part of the relaxations ascribed to protein hydration. First, only a very small part of the hydration could