烯烃聚合催化剂的ESR研究进展

很多烯烃聚合催化剂都含有过渡金属离子. 由于很多过渡金属离子存在未成对电子,ESR可以检测这些含有未成对电子的过渡金属离子,所以ESR检测技术可以被用于聚烯烃催化剂的研究. 该文综述了近年来ESR技术在烯烃聚合催化剂表征领域的研究进展,根据不同过渡金属分类讨论,主要涉及了Ti、Ni、V、Cr等几种常见的过渡金属催化剂的ESR研究.     

紧凑型电子自旋共振(ESR)仪

描述了一种原创的紧凑型电子自旋共振(ESR)仪.该仪器具备高性能、低成本、简单可靠、结构紧凑、开放构架、多功能模块等一系列特点.分析了ESR谱仪的多个微波单位,研发并通过实验验证了自差ESR谱仪的最优双腔结构,并设计了一种可提供高均匀磁场的电、永磁混合磁体.最后介绍了这种新型紧凑型电子自旋共振仪的主要参数和应用.     

谱-空间2D ESR成像

在Bruker ER 200D ESR 谱仪上安装一套自制的谱-空间2D ESR成像系统,这套系统由一对梯度场线圈、电源、微机及图像重建程序组成. 用滤波反投影图像重建方法,实现了两种自由基样品的谱-空间2D ESR成像,由2D 图像得到样品中自由基的自旋密度空间分布及相应的波谱参数. 讨论了成像参数与图像精度的关系.     

多自由基体系溶液ESR谱的数据分析

将ER-200D ESR波谱仪ASPECT 3000计算机采集的ESR图谱传输到IBM PC/XT计算机上,通过自行设计的ESR图谱模拟程序ESRSIMU,同屏显示比较,方便、灵活地对多自由基体系溶液ESR一级近似谱进行了模拟,获取了各个自由基的ESR波谱参数和体系中各类自由基的相对浓度等信息.对单个自由基ESR谱的模拟,ESRSIMU的运行速度比BRUKER EPR 3002快近100倍.     

卷积差技术在ESR和ESR成像中的应用

该文将卷积差技术应用于提高ESR谱的分辨率和在ESR成像过程中扣除固有线宽介绍了卷积差过程,对比了卷积差前后ESR谱的变化.     

电子自旋共振技术在生物领域的应用进展

电子顺磁共振(ESR)技术是一种研究顺磁性物质的未成对电子结构和动力学信息的波谱检测方法。近年来ESR技术在生物医学领域得到了广泛的应用,如解析含有过波金属离子的单分子磁体的构象与功能,金属蛋白酶结构和催化机理,自由基相关的电子传递过程等。目前,随着电子顺磁共振技术向微观世界探索的深入,一种基于NV的微观自旋磁共振技术日趋成熟,甚至达到了单分子单自旋的探测水平。本文综述了ESR技术在生物学领域应用的原理方法和研究进展,以及微观SER技术等的应用原理和进展,为更好地将ESR技术应用在蛋白质单分子结构解析与动力学研究、自由基反应途径解析,自旋标记分子的细胞内定位等提供参考和借鉴。     

五种氨基酸钆络合物的ESR波谱

迄今未见任何稀土氨基酸络合物的ESR波谱报道,本文在合成Gd³⁺分别与甘氨酸、β-丙氨酸、谷氨酸、天冬氨酸和天冬酰胺五种氨基酸络合物的基础上,测定了不同温度下,水溶液、粉末及分子筛吸附样品的ESR谱,讨论了络合物中晶体场强,对称性及成键特性。     

磷酸盐、氟磷酸盐和氟化物玻璃中过渡金属离子的顺磁共振研究(Ⅱ)Co~(2 ),Ni~(2 )

低温77K下,在三种玻璃中都观察到了Co~(2 )的ESR信号,认为Co~(2 )是处干四面体格位,从实验所得的有效g值,判别出中心离子与配位体间化学键的性质变化,本文还研究了氟磷酸盐玻璃中Ni~(2 )ESR,辨认了Ni~(2 )的谱线,用自旋哈密顿作了比较详细的分析计算,并解释了一般氧化物玻璃中很难观察到Ni~(2 )的ESR的原因。     

储锂硅材料的ESR谱研究

采用了电化学方法制备储锂硅材料,并用电子自旋共振(ESR)方法进行研究. 实验结果表明, 储锂前的硅ESR行为符合居里自旋的ESR特征, ESR信号主要来源于硅材料中的晶格缺陷、 表面悬空键等局域化自旋中心. 储锂后硅材料中产生了泡利自旋,居里自旋的强度比储锂前增大2～3倍. 此外,对硅和储锂硅ESR谱线的g因子和ΔH_pp随温度的变化情况也进行了分析. 硅材料电化学储锂时,与锂离子中和的电子主要参与形成Li-Si共价键,对ESR信号贡献很小.     

冷冻固化红细胞膜的ESR波谱

本文介绍了两种获得红细胞膜ESR谱的方法。第一种是采用冷冻干燥红细胞膜、图谱是在室温条件下测得;第二种是选用冷冻固化新鲜红细胞膜样品。两种方法得到的ESR谱都显示出随磁场取向的各向异性,这很可能是由于细胞膜之间的磁相互作用所引起的。在图谱中出现的g=2.0062信号是由于超氧离子自由基激发产生的其他自由基信号。     

绿茶中茶多酚的2D NMR研究

用2D NMR技术研究了从绿茶中分离得到的4种儿茶素和2种鞣质,对其¹H和¹³C NMR谱线作了全归属.     

Identification and characterization of proanthocyanidins of 16 members of the Rhododendron genus (Ericaceae) by tandem LC-MS

The proanthocyanidins of the leaves of 16 taxa of the Rhododendron genus (Ericaceae) [Rhododendron 'Catawbiense Grandiflorum', Rhododendron 'Cunningham's White', Rhododendron smirnowii Trautv., Rhododendron calophytum Franch., Rhododendron dichroanthum ssp. scyphocalyx (Balf. f. & Forrest ) Cowan, Rhododendron micranthum Turcz., Rhododendron praevernum Hutch., Rhododendron ungernii Trautv., Rhododendron kaempferi Planch., Rhododendron degronianum ssp. heptamerum var. hondoense (Nakai ) H. Hara, Rhododendron fortunei Lindl., Rhododendron ponticum L., Rhododendron galactinum Balf. f. ex Tagg., Rhododendron oreotrephes W. W. Sm., Rhododendron brachycarpum ssp. brachycarpum D. Don ex G. Don, and Rhododendron insigne Hemsl. & E. H. Wilson ] were investigated qualitatively by liquid chromatography-mass spectrometry in series. Twenty-nine dimeric proanthocyanidins based on (epi)catechin and (epi)gallocatechin were detected and characterized on the basis of their unique fragmentation pattern in the negative ion mode tandem mass spectrometry spectra. All of them were extracted for the first time from these sources, and ten of them were not reported previously in nature. The position of the galloyl residue was assigned on the basis of the retro-Diels-Alder fragmentation and the dehydrated retro-Diels-Alder fragmentation; it resulted from the loss of gallic acid as a neutral loss in the negative ion mode. Furthermore, four caffeoylquinic acids, six p-coumaroylquinic acids, epigallocatechin, gallocatechin, catechin, epicatechin, epigallocatechin gallate, catechin gallate, epicatechin gallate, gallocatechin gallate, two quercetin-O-hexosides, quercetin-O-galloyl-hexoside, quercetin-O-pentoside, quercetin-O-rhamnoside, quercetin-O-pentoside-O-hexoside, quercetin-O-rhamnoside-O-hexoside, quercetin-O-feruloyl-hexoside, quercetin-O-(p-hydroxy)benzoyl-hexoside, taxifolin-O-pentoside, myricetin-O-rhamnoside, two myricetin-O-pentosides, three myricetin-O-hexosides, and two myricetin-O-galloyl-hexosides were detected and shown to possess characteristic tandem mass spectrometry spectra and were tentatively assigned on the basis of their retention time.     

Effect of polyphenolic structure and mass ratio on the emulsifying performance and stability of emulsions stabilized by polyphenol-corn amylose complexes

O/W emulsions stabilized by polyphenol/amylose (AM) complexes with several polyphenol/AM mass ratios and different polyphenols (gallic acid (GA), epigallocatechin gallate (EGCG) and tannic acid (TA)) were prepared by a high-intensity ultrasound emulsification technique. The effect of the pyrogallol group number of polyphenols and the mass ratio of polyphenols/AM on polyphenol/AM complexes and emulsions was studied. The soluble and/or insoluble complexes gradually formed upon adding polyphenols into the AM system. However, insoluble complexes were not formed in the GA/AM systems because GA has only one pyrogallol group. In addition, the hydrophobicity of AM could also be improved by forming polyphenol/AM complexes. The emulsion size decreased with increasing pyrogallol group number on the polyphenol molecules at a fixed ratio, and the size could also be controlled by the polyphenol/AM ratio. Moreover, all emulsions presented various degrees of creaming, which was restrained by decreasing emulsion size or the formation of a thick complex network. The complex network was enhanced by increasing the ratio or pyrogallol group number on the polyphenol molecules, which was because the increasing number of complexes was adsorbed onto the interface. Altogether, compared to GA/AM and EGCG/AM, the TA/AM complex emulsifier had the best hydrophobicity and emulsifying properties, and the TA/AM emulsion had the best emulsion stability.     

近红外光谱法快速检测绿茶中儿茶素的含量

提出了一种应用傅里叶近红外漫反射光谱分析技术快速检测茶叶中主要儿茶素含量的新方法.首先获取茶叶在10000～4000 cm<'-1>范围的近红外漫反射光谱,然后以高效液相色谱分析值作参考值.采用偏最小二乘法建立茶叶中表没食子儿茶素没食子酸酯(EGCG)、表儿茶素没食子酸酯(ECG)和表没食子儿茶素(EGC)含量的定量分析模型.通过交互验证方法来优化模型的主成分数和所采用的光谱预处理方法.EGCG、ECG和EGC三个模型预测值和参考值问的相关系数分别为0.9800、0.9763和0.9853,预测均方根误差分别为0.3509、0.1147和0.1365.研究结果表明,近红外光谱技术可成功地检测茶叶中EGCG,ECG和EGC的含量.     

Irradiation of Phenolic Compounds with Ultraviolet Light Causes Release of Hydrated Electrons

Phenolic compounds are widely used for a number of purposes, including medical drugs, cosmetics, food additives, and supplementary foods, and are often exposed to the ultraviolet (UV) rays of the sun. We herein examined free radicals produced from phenolic compounds by UV irradiation using an electron paramagnetic resonance (ESR)-spin trapping technique with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The ESR signals of DMPO adducts of the hydrogen radical (DMPO–H) and hydroxyl radical were detected following the UV irradiation of polyhydric phenols, such as hydroquinone, catechol, resorcinol, pyrogallol, and methyl gallate, in an aqueous solution. Radical adducts were not detected in monohydric phenols, such as phenol and methylparaben. The signal intensity of DMPO–H became stronger as the concentration of phenolic compounds increased. The signal intensity of DMPO–H decreased when the solution in which air was replaced with N₂O, a scavenger of hydrated electrons, was irradiated. However, sodium formate, a scavenger of the hydrogen radical, did not affect the signal intensity of DMPO–H. The signal intensity of DMPO–H became stronger as the pH of the solution increased. Semiquinone-type radicals increased following the UV irradiation of solutions of polyhydric phenols in the absence of DMPO. These results indicate that hydrated electrons are generated by the UV irradiation of polyhydric phenols, and that phenoxide ions are responsible for the production of hydrated electrons.     

紫外光诱导下的固体胆红素自由基性质的ESR研究

利用电子自旋共振方法对固体胆红素及其自由基在紫外照射下的变化进行了研究,发现在紫外光下仅引起胆红素超氧自由基及半醌自由基浓度的增加,而没有新的自由基形式生成,指出Foote提出的光氧化机理假说的中间体自由基即是由上述两种自由基构成,并通过电子计算机对ESR谱的摸拟,提出了紫外辐照下的胆红素自由基形成机理,推测胆红素光化学反应的途径及产物与这两种自由基浓度及在不同环境下的反应活性有关.     

胰岛素与其受体分子相互作用的ESR的波谱研究

本文首次制备了胰岛素氮氧自由基,研究了胰岛素探针与其受体结合过程中ESR波谱参数的动力学变化.实验表明胰岛素与其受体结合前后,膜蛋白质的构象、胰岛素分子的旋转相关时间(τ_c)和胰岛素氮氧自由基的ESR波谱振幅(h₀)均发生明显的变化,这些变化均与胰岛素-受体的内噬现象有关系.当封闭受体上的巯基、氨基或羟基时,胰岛素与其受体的结合能力便受到一定的阻抑作用.     

茶多酚对鼠心肌缺血再灌产生氧自由基的清除

用电子顺磁共振(Electron Spin Resonance,缩写ESR)在低温110K条件下,以离体大鼠心脏缺血再灌为模型,直接测量了缺血再灌损伤时产生的活性氧自由基信号.实验发现,缺血再灌损伤的心肌中氧自由基的含量比正常灌流心肌增加了188%,茶多酚可以使其降低71%。这说明茶多酚对氧自由基引发的缺血再灌损伤有保护作用。     

Hypocrellin A与二苄胺和N-甲基苄胺的光化学反应

为了探讨HypocrellinA (HA)与胺基衍生物反应的自由基形成机制 ,我们采用ESR谱分别研究了HA与二苄胺 (DBA)和N 甲基苄胺 (NMBA)的光化学反应 .在含胺类物质和溶解氧的溶剂系统下 ,可见光照射HA激发成HA ,然后将溶解氧转变成1O2 ,1O2 诱导DBA或NMBA的氯仿溶液都能产生半醌自由基和氮氧自由基 .氮氧自由基的信号强度随光照时间的增加而减弱 ,而半醌自由基的信号强度随光照时间的增加而增强 ,氮氧自由基的含量与光照产生的半醌自由基成反比 .在除氧条件下 ,光照含HA和DBA的氯仿溶液体系时 ,半醌自由基是主要的自由基 .结果表明 ,在有氧的氯仿溶液中 ,HA诱导胺类物质生成HA半醌自由基     

茶多酚对6-OHDA诱导的SH-SY5Y细胞凋亡的保护作用

茶多酚在体内具有广泛的生物活性和药理作用,有助于预防与氧化应激相关的疾病,比如癌症,心血管疾病,神经退行性疾病和衰老. 氧化应激参与了帕金森病（PD）的病理进程. 活性氧在PD的发病机制中发挥了重要的作用,氧自由基直接损伤细胞膜引起脂质过氧化,损伤蛋白质和各种功能酶引起蛋白质沉淀,诱导促凋亡因子的表达,损伤DNA,最终导致了细胞的凋亡. 然而,关于茶多酚对PD的预防和治疗作用目前还不清楚. 本文应用氧化应激诱导的PD病理细胞模型,评价了茶多酚的神经保护作用. 结果表明茶多酚这类植物天然抗氧化剂对氧化应激诱导的细胞凋亡具有明确的抑制作用. 实验中我们选择了6-OHDA诱导的SH-SY5Y细胞作为细胞模型, 运用了MTT、流式细胞术、荧光显微成相, 竞争性ELISA和蛋白质杂交等方法研究了SH-SY5Y细胞的凋亡特性. 结果表明,6-OHDA对SH-SY5Y有时间-浓度依赖性细胞毒性,100 μmol/L 6-OHDA处理24 h,细胞活力减少50 %,同时伴随着活性氧增加（用ＥＳR）,线粒体膜电位降低,细胞内钙离子和一氧化氮增加,nNOS和iNOS表达量上升及蛋白结合的硝基酪氨酸水平升高. 单独茶多酚处理对细胞没有太大的影响,而茶多酚预处理可显著降低6-OHDA所产生的细胞毒性. 溶液实验证明,茶多酚对6-OHDA的自氧化有浓度-时间依赖性抑制作用（用ＥＳＲ）. 本研究表明茶多酚可能是通过活性氧-一氧化氮途径,减少过氧亚硝基的生成来对6-OHDA诱导的细胞凋亡表现保护作用的. 本文的实验结果提示茶多酚在治疗PD等慢性神经退行性疾病上可能是一种有着潜在疗效的药物.