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首页> 外文期刊>Journal of chemical crystallography >Crystal and molecular structure of glutaconic acid
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Crystal and molecular structure of glutaconic acid

机译：谷氨酸的晶体和分子结构

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Crystals of Glutaconic acid, C5O4H6, are triclinic, space group P (1) over bar, with the cell dimensions (294) K, a=4.831(1) Angstrom, b=10.188(1) Angstrom, c=12.609(1) Angstrom, alpha=83.46(1)degrees, beta=80.02(1)degrees, gamma=78.71(1)degrees, V=598.8 Angstrom(3) with D-m=1.47, D-x=1.443 g.cm(-3). There are two independent molecules in the asymmetric unit. The crystal structure was solved by multi solution techniques with three-dimensional data collected (to the limit of 2theta(max) of 154degrees for Cu Kalpha) on a CAD-4 diffractometer. The crystal structure was refined by full matrix least squares method to a final R value of 0.058 for 1894 reflections (Igreater than or equal to2sigma). The two independent molecules are conformationally similar. In both the molecules, the carboxyl ends are trans to each other with respect to the central C=C double bond in the structure. The molecules are self-paired through dimeric type of hydrogen bonding involving the terminal carboxyl groups, characteristic of many dicarboxylic acid structures. The crystal structure is stabilized by a series of O-H...O hydrogen bonds of the glutaconic acid dimeric units. Free radicals have been shown to be involved in a number of chemical and biological processes and lipid peroxidation is one such process. Glutaconic acid was chosen as a simple unsaturated model of a fatty acid. When irradiated with X-rays, it was found to form a stable free radical structure. ESR (electron spin resonance) and ENDOR (electron nuclear double resonance) studies were used to characterize the free radical structure and correlate with the X-ray structure. The free radical was found to be HOOC-CH=CH-CH-COOH with the glutaconic acid in the trans conformation. The damage occurs at the alpha-carbon atom (the first carbon of the double bond). The damage consists of a loss of an hydrogen atom. This results in an unpaired electron in the p-orbital delocalized over the three central carbon atoms. The two alpha-proton couplings were resolved in the ENDOR spectrum. ESR spectra show that the two molecules are magnetically similar that is in agreement with the crystal structure that reveals that the two independent molecules are conformationally similar. This is the characteristic type of damage that occurs in lipids when they form free radicals that in turn reacts with oxygen and other compounds and ultimately results in cellular damage. [References: 16]
机译：谷氨酸C5O4H6晶体是三斜晶系，在棒上为空间群P（1），晶胞尺寸为（294）K，a = 4.831（1）埃，b = 10.188（1）埃，c = 12.609（1）埃，α= 83.46（1）度，贝塔= 80.02（1）度，伽马= 78.71（1）度，V = 598.8埃（3），Dm = 1.47，Dx = 1.443 g.cm（-3）。不对称单元中有两个独立的分子。晶体结构是通过多溶液技术解决的，该技术在CAD-4衍射仪上收集了三维数据（对于Cu Kalpha，限制为154度的2θ（最大值）为154度）。通过全矩阵最小二乘法将晶体结构精炼到1894次反射的最终R值为0.058（大于或等于2σ）。两个独立的分子在构象上相似。在两个分子中，羧基末端相对于结构中的中心C ＝ C双键彼此反式。通过涉及末端羧基的氢键的二聚体类型，分子是自配对的，这是许多二羧酸结构的特征。谷氨酸二聚体单元的一系列O-H ... O氢键使晶体结构稳定。自由基已被证明参与许多化学和生物过程，脂质过氧化就是其中之一。选择谷氨酸作为一种简单的脂肪酸不饱和模型。当用X射线照射时，发现其形成稳定的自由基结构。 ESR（电子自旋共振）和ENDOR（电子核双共振）研究用于表征自由基结构并与X射线结构相关。发现自由基是带有反式构型的戊二酸的HOOC-CH ＝ CH-CH-COOH。损伤发生在α-碳原子（双键的第一个碳原子）处。损害包括氢原子的损失。这导致在p轨道上不成对的电子在三个中心碳原子上散布。在ENDOR光谱中解析了两个α-质子耦合。 ESR光谱显示，这两个分子在磁性上相似，这与揭示两个独立分子在构象上相似的晶体结构一致。这是脂质形成脂质的特征类型，当脂质形成自由基时会与氧气和其他化合物发生反应，最终导致细胞损伤。 [参考：16]

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