ESR of Gamma Irradiation and Ultraviolet Photolysis Products in Some Tetrasubstituted Ammonium Compounds

Abstract

The electron spin resonance of gamma and ultraviolet irradiated tetrabutylammonium halides [CH₃(CH₂)₃]₄NX (X=I,Cl,Br), tetrabutylammonium hydrogen sulfate [CH₃(CH₂)₃]₄NHSO₄, tetrabutylammonium periodate [CH₃(CH₂)₃]₄NIO₄, and ultraviolet photolyzed tetramethylammonium iodide, (CH₃)₄NI, and tetramethylphosphonium iodide, (CH₃)₄PI have been investigated between 140 and 350 K. The gamma and ultraviolet irradiation damage centers in tetrabutylammonium compounds were attributed to CH₃—CH^…—CH^…—CH₂, radicals, and ultraviolet photolysis damage centers in tetramethylammonium and phosphonium iodides were attributed to ?H₃ radicals. The g values of both radicals are found to be isotropic and g = 2.0030 and 2.0037 respectively to the methylallyl and the methyl radicals. The hyperfine coupling constants of the free electron to the protons in the radicals are reported and discussed.     

电子自旋共振(ESR)技术在生物和医学中的应用

电子自旋共振(electron spin resonance,ESR)是检测自由基最直接最有效的方法,是自由基生物学和医学不可缺少的重要研究技术. 作者综述了ESR、自旋标记、自旋捕集和ESR 成像技术的最新发展及ESR技术在细胞膜、蛋白质结构和一些重大疾病如心脏病、老年痴呆症、帕金森综合症和中风等疾病研究及辐射损伤和植物疾病研究中的应用.     

Radiostability of Allantoin by Using Electron Spin Resonance Spectroscopy

The radiosterilization potential and dosimetric feature of allantoin were investigated through the molecular degradations produced after ultraviolet and gamma irradiation using electron spin resonance, infrared, and ultraviolet spectroscopies and thermal measurement techniques (differential thermal analysis and the glass transition temperature). Although ultraviolet-irradiated allantoin presents no electron spin resonance signal, gamma irradiation exhibited an electron spin resonance signal of triplet appearance. Room temperature and high-temperature line intensity and spectrum area data and their variations with applied microwave power, storage time, annealing time, annealing temperature, and applied radiation dose were analyzed by assuming the production of two different types of radicals having different spectroscopic and decay characteristics. Based on its relatively stable nature toward gamma and ultraviolet radiations, it was concluded that allantoin itself and the products containing it can be sterilized by gamma and/or ultraviolet radiations without creating a great loss in its beneficial effects in the allowed radiosterilization dose limits.     

Spin Trapping of Alkoxycarbonyl Radicals from the Photolysis of Alkoxycarbonylmercury Compounds

Irradiation of alkoxycarbonylmercury compounds in benzene in the presence of nitrone radical traps leads to the scavenging of alkoxycarbonyl radicals.     

Electron Spin Resonance Study of the Solvent Effect on the Conformation of Some Iminoxy Radicals

The reaction of nitrogen dioxide with carbonyl compounds having a methylene or vinyl group adjacent to the corbonyl leads to the formation of stable iminoxy radicals^1-3. Evidence^1,2,4 has been presented that the precursor of these iminoxy radicals is probably the corresponding oxime formed by rearrangements of the intermediate nitroso compounds. There have also been reports on the e.s.r. detection of some cis-trans isomers of some iminoxy radicals in methanol or in neat liquid^1,5. We wish to report here a drastic solvent effect on the conformations of some iminoxy radicals formed by the reaction of NO₂ with trifluoroacetylacetone.     

ESR自旋捕集技术的发展和在生物医学研究中的应用

ESR是研究自由基最直接和最有效的技术,但是这些自由基必须是相对稳定的,而且要达到一定浓度才能用ESR技术检测和研究. 而生物体系中产生的自由基大部分是不稳定的,这是常规ESR波谱仪无法检测的. 为了克服ESR技术的这一局限性,发展了自旋捕集技术,这是目前研究生物和医学体系中活泼自由基应用最多也是最成功的方法, 每年都有新的自旋捕集剂合成和大量在生物医学应用的报道,为自由基生物医学的研究和发展做出了巨大贡献.  作者建立和发展了捕捉超氧阴离子自由基、羟基自由基、脂质过氧化产生的脂类自由基、一氧化氮自由基和单线态氧及一氧化氮和氧自由基同时检测技术. 利用这些技术开展了细胞、组织产生自由基机理,天然抗氧化剂的筛选及一些重大疾病如炎症、心脏病、老年痴呆症、帕金森综合症,中风,辐射损伤,蛋白质氧化,植物光合系统中产生活性自由基和植物的发病机理研究中的应用,取得了一系列研究结果.     

Magnetic and Spin Effects in Photolysis of Aqueous Solutions of Cyclopentanone

Chemical nuclear polarization in photolysis of aqueous solutions of cyclopentanone has been studied. The products of the photolysis of liquid and frozen solutions have been determined. Kinetic investigations were carried out at different temperatures. The influence of an external magnetic field (0.37 T) and of a gradient magnetic field produced by barium hexaferrite and Nd₁₅Fe_62.5B_5.5Co₁₆Al₁ plates has been revealed. The mechanisms underlying the appearance of magnetic and spin effects are discussed.     

轨道诱导Peierls相变材料MgTi_2O_4的电子自旋共振研究

用变温电子自旋共振手段(Electron Spin Resonance,ESR),对轨道诱导Peierls相变MgTi_2O_4体系进行了研究.研究发现,轨道诱导Peierls相变所伴随的自旋二聚相变对ESR谱产生了影响.在相变温度以上,MgTi_2O_4的磁性为顺磁行为.而在相变温度以下,ESR谱显示MgTi_2O_4的磁性偏离了顺磁行为.对ESR谱线的参数拟合结果显示,MgTi_2O_4在发生轨道诱导Peierls相变时,自旋耦合作用逐渐增强.这说明:自旋耦合作用的增强很有可能是导致相变的一个重要的因素.     

轨道诱导Peierls相变材料MgTi2O4的电子自旋共振研究

用变温电子自旋共振手段,对轨道诱导Peierls相变MgTi2O4体系进行了研究。研究发现,轨道诱导Peierls相变所伴随的自旋二聚相变对ESR谱产生了影响。在相变温度以上,MgTi2O4的磁性为顺磁行为。而在相变温度以下,ESR谱显示MgTi2O4的磁性偏离了顺磁行为。对ESR谱线的参数拟合结果显示,MgTi2O4在发生轨道诱导Peierls相变时,自旋耦合作用逐渐增强。这说明:自旋耦合作用的增强很有可能是导致相变的一个重要的因素。     

Electron Spin Resonance Study of Yttrium Aluminum Garnet Films Doped with Nd and Yb Ions

Yttrium aluminum garnet (YAG) thin films doped with optical active rare earth ions grown on YAG substrate can be used as wave-guide laser. Measured layers YAG:Yb, Nd (grown by the isothermal liquid phase epitaxy (LPE)) was additionally doped with Ga and Lu ions in order to increase film refractive index and decrease strains in layers, respectively. Electron spin resonance measurements have been performed on a number of YAG:Yb, Nd thin films with Yb concentrations ranging from 0at.% to 15at.% and Nd concentration equals to 1 at.% and 3 at.%. It was found that the measured angular dependence of the Yb^3? ion linewidth is typical for a mosaic structure. Moreover, it was shown that internal strains in the layers depend on the kind of dopant as well as on their concentration.     

激光光解苯甲醛自由基的时间-分辨ESR研究

利用高时间分辨ESR波谱仪,对苯甲醛为光敏分子的各体系进行了CIDEP(化学诱导动态电子极化)研究,揭示了苯甲醛体系的CIDEP信号的产生过程,并进一步确认了其产生过程中的极化特征.     

淀粉自由基弛豫发光

为了研究淀粉自由基的变化规律,以生物光子辐射理论为基础.根据化学发光的动力学模型,建立了淀粉自由基的发光动力学方程,并根据自由基发光强度与自由基浓度的关系,通过分析得到了淀粉自由基的湮没方程,得到了光强随时间的变化函数.通过拟合发现,函数在不同温度下随时间的变化曲线与实验曲线的相关系数都在0.98以上,能很精确地刻画自由基的弛豫发光规律.     

在体电子自旋共振(EPR)波谱和成像技术在生物医学中的应用

活性氧和氮自由基(ROS/RNS)在一系列的人类疾病中扮演着双重角色. 它们可以是氧化剂, 诱导氧化状态, 导致组织损伤. 它们又可以是信号传导因子, 诱发保护性反应, 使得被调节的组织器官经受得起更强的损伤. 鉴于它们在生物医学中的重要作用, 检测它们产生和分布的技术的研究因而变得必要和紧迫. 在体电子自旋共振(EPR)波谱和成像技术渐已被应用于活体生物体系中用以表针和显像ROS/RNS. EPR 波谱特性(包括线宽、强度和寿命)以及空间分布信息已为动物甚至人体病理模型中氧化还原状态和氧分布的检测提供不可缺少的依据. 该文将简单描述和讨论一系列在体EPR 波谱和成像技术在器官和组织中的应用, 其中包括活体组织氧化还原状态, 活体组织氧分布和时间演化, 自由基空间以及谱-空间成像等.     

Measurement of Microviscosity in Vesicular Membranes by Electron Spin Resonance

The seven vesicular formulations CER(−), CER(+), CER(I), PC(−), PC(+), DAG(B) and DAG(I) have been developed using ceramide IIIB (CER), phosphatidylcholine (PC), or diacylglycerides (DAG) as main lipid components. B and I indicate the processed hydrophilic surfactant Brij 58 and Imwitor 375, (+) and (−) symbolize the positive and negative zeta potential. The influence of the bilayer microviscosity on the features of lipid vesicles as dermal drug delivery system is widely discussed, but comparable and reproducible results could not be found. For the measurement of the microviscosity by electron spin resonance the lipophilic spin probe of 14-doxylpalmitoylic acid methyl ester (DPME) was incorporated into the bilayer. Rotational correlation times (τ_c) between 0.3 and 1.8 ns were calculated. The dynamic viscosities (η) of eight different medium-chained triglycerides–castor oil mixtures in the range between 25 and 948 mPa · s, as well as the corresponding τ_c values of DPME in these mixtures, were determined to establish a calibration curve for the estimation of the microviscosity. The microviscosities of the vesicle membranes increase from 40 to 565 mPa · s in the following order DAG(B) = DAG(I) < PC(−) ≈ CER(I) < CER(−) ≤ CER(+) < PC(+). The microviscosity of 49.8 ± 2.5 mPa · s in pure unsaturated soy PC membranes decreases on adding the sodium cholate to 28.3–29.4 mPa · s, whereas the addition of dilauroylphosphatidylcholine in repeated freeze–thaw cycles or 8.5% ethanol in the hydrophilic phase had no influence. Authors' address: Hans-Hubert Borchert, Institute of Pharmacy, Free University of Berlin, Kelchstrasse 31, Berlin 12169, Germany     

辐射引发和热引发聚丙烯腈纤维的自由基研究

利用电子自旋共振波谱(ESR)研究了聚丙烯腈(PAN)纤维在真空以及空气气氛下经γ射线辐射引发和热引发产生的自由基. 结果显示,室温下辐射诱导产生的自由基为烷基自由基和聚亚胺自由基,辐射产生的自由基随温度升高而衰减,150 ℃时完全消失. 热引发的自由基则依赖于温度和氧气, 当PAN纤维在空气中加热至190 ℃时,开始产生多烯自由基,而且自由基浓度随温度升高而迅速增加;在真空条件下,PAN纤维经加热只产生极少量自由基. 据此推断,热引发自由基是通过热氧化反应产生的,这类自由基位于共轭结构上,其共轭长度也随温度的升高而增加.     

时间分辨ESR与电子自旋极化研究

介绍了近年发展起来的时间分辨TRESR技术，以3个实例介绍了用TRESR研究光解自由基的电子自旋极化的状况，指出研究自旋极化可以得到关于分子激发态和自由基反应动力学等丰富的多方面信息，TRESR技术是研究光与分子相互作用的一种重要手段。     

微波电子自旋共振实验波形分析

详细分析了微波段用可调反射式谐振腔做电子自旋共振实验中共振信号的形成原理,分析指出下凹和上凸波形都为共振吸收信号,当波形的上下两部分等大时,为色散信号,波形的上下两部分不等大时,为色散信号和共振吸收信号的合成。从理论上解释了共振信号的变化所反映的物理过程。     

基于极紫外自由电子激光的中性团簇红外光谱

团簇在能源催化和大气雾霾等诸多化学过程中广泛存在,团簇表征与性能研究对诠释化学反应机理至关重要. 然而,中性团簇由于缺乏电荷、难于探测,实验研究非常困难. 鉴于上述情况,发展了基于极紫外自由电子激光的中性团簇红外光谱实验方法,用于质量选择中性团簇的高灵敏探测、结构表征和性能研究. 红外-极紫外衰减和红外+极紫外增强光谱实验方法已被应用于一些中性水团簇和一些中性金属羰基化合物的研究. 由于极紫外自由电子激光的波长范围涵盖了绝大多数中性团簇的第一电离势,这一独特的实验方法为开展各类中性团簇红外谱学和结构的研究打开了大门. 本文综述了这些红外光谱实验方法及其在中性团簇研究中的应用.     

用微米级LaNi5为催化剂生长的碳管的ESR谱研究

用微米级LaNi₅合金粉末为催化剂, 以乙炔为原料, 采用化学气相沉积(CVD)法合成了多壁碳纳米管. 在100~290 K温度下测量了41 μm≤d≤150 μm粒径催化剂制备的不同直径分布的碳纳米管的电子自旋共振（ESR）谱,研究了测量温度、微米级催化剂粒径及制备过程的氢气氛对生成的碳纳米管的ESR谱线型、g因子、线宽的影响. 发现碳纳米管的g因子随其直径的增大而增大,分别为2.040 0（催化剂粒径41 μm≤d≤50 μm, 碳纳米管的直径分布为10 nm到20 nm）和2.089 8（催化剂粒径100 μm≤d≤150 μm,碳纳米管的直径分布为70 nm到120 nm）. 发现小管径纳米管的ESR谱图有一个峰, 而大管径纳米管的ESR谱图有两个峰A和B, 且随测量温度的升高, 峰B强度增大.