氯代烃光解活泼自由基的ESR研究

本文用2,4-二硝基苯亚甲基特丁基氮氧化物(DNPBN)作自由基捕捉剂研究了氯代烃光解过程产生的自由基中间体。实验结果表明在汞灯照射下键能较低的多氯代烷烃分子中的碳-氯键极易发生均裂而产生碳中心自由基与活泼的氯原子, 并且后者可被DNPBN捕获, 形成颇为稳定的氮氧自由基加合物[Cl-DNPBN]~·。对多氯代苯,随着取代氯原子数目增多, 加合物[Cl-DNPBN]~·的ESR信号强度也明显增加。此外, DNPBN对氯原子的大量捕捉实验还证明它对氯原子是一种高效的特征捕捉剂。     

氯代烃光解活泼自由基的ESR研究

本文用2,4-二硝基苯亚甲基特丁基氮氧化物(DNPBN)作自由基捕捉剂研究了氯代烃光解过程产生的自由基中间体。实验结果表明在汞灯照射下键能较低的多氯代烷烃分子中的碳-氯键极易发生均裂而产生碳中心自由基与活泼的氯原子,并且后者可被DNPBN捕获,形成颇为稳定的氮氧自由基加合物[Cl-DNPBN]~·。对多氯代苯,随着取代氯原子数目增多,加合物[Cl-DNPBN]~·的ESR信号强度也明显增加。此外,DNPBN对氯原子的大量捕捉实验还证明它对氯原子是一种高效的特征捕捉剂。     

脂二胺在颜料分散体中光化学反应活泼自由基的ESR研究

用自旋捕捉技术与ESR相结合的方法研究了脂二胺在ZnO、TiO₂的庚烷或苯的分散体系中光诱导的电子转移过程。观察到DMPO与氮中心自由基加合物的ESR信号,表明捕捉到的自由基是脂二胺与光生空穴作用而产生的胺的阳离子自由基。     

脂氧合酶催化双高-γ-亚麻酸脂质过氧化产生的碳自由基的结构确证

采用液相色谱-电子自旋共振波谱(LC/ESR)联用技术、液相色谱-质谱(LC/MS)联用技术结合自旋捕集技术,研究了脂氧合酶(LOX)催化双高-γ-亚麻酸(DGLA)脂质过氧化过程中产生的碳自由基.以α-[4-吡啶基-1-氧]-N-叔丁基氮酮(POBN)为自旋捕集剂,在LOX-DGLA反应混合物中与碳自由基形成自旋加合物后,根据各加合物在LC/UV/ESR和LC/MS中对应的保留时间,确定加合物的分子量,进一步根据加合物质谱裂解方式确定其结构.结果表明,在LOX催化DGLA脂质过氧化过程中产生的碳自由基主要包括~·C_7H_(13)O_2,~·C_(10)H_(17)O_2和~·C_5H_(11),分别来自DGLA脂氧自由基(8-,11-,15-LO~·)的β-裂解.此结果有利于进一步研究DGLA在体内的脂质过氧化过程及该过程中产生的碳自由基的生理作用.     

γ射线辐照的多晶态嘧啶核苷类中自旋捕捉自由基的ESR研究——Ⅱ.胸苷和脱氧胞苷盐酸盐

本文以NtB(亚硝基特丁烷)为捕捉剂,利用自旋捕捉(Spin Trapping)和ESR方法,研究了γ射线辐照的多晶态胸苷和脱氧胞苷盐酸盐中产生的室温自由基。对它们分别确定了三种类型与两种类型的碱基自由基,此与单晶ESR研究结果完全一致,从而获得它们R·自旋加合物的标准ESR波谱。此外,对脱氧胞苷盐酸盐还确定了在单晶ESR研究中未被鉴别的核糖自由基HO(5′)HC(4′)H<及由其演变而成的—(5′)H_2自由基。     

[Z]-2-(芳基锡基)-1-(9-芴醇)乙烯的合成、结构与性质

用三苯基氢化锡,三对甲苯基氢化锡作为锡氢化试剂与9-乙炔基-9-芴醇进行反应,合成了2个有机锡化合物:[Z]-2-(三苯基锡基)-1-(9-芴醇)乙烯(1)和[Z]-2-(三对甲苯基锡基)-1-(9-芴醇)乙烯(2)。化合物1和2分别与ICl,Br~2,I~2反应,得到6个有机锡一卤化物,6个有机锡二卤化物和2个有机锡混合卤化物(3-16)。有机锡一碘化物7,13和有机锡二碘化物8,14与KOH乙醇溶液反应,分别得到相应的有机锡氢氧化物17,18和有机锡氧化物19,20。有机锡二碘化物8,14分别与含氮双齿配体1,10-邻菲罗啉(Phen),2,2'-联吡啶(Bipy),8-羟基喹啉(Oxin)反应,得到6个相应的配合物21-26。26个新化合物通过元素分析,锡含量测定,IR,^1HNMR测定对其结构进行了表征。同时测定了化合物2的晶体结构,晶体属单斜晶系,空间群P2~1/c。化合物2是以Sn原子为中心扭曲的四面体构型。     

电极过程自由基中间体的ESR研究(Ⅳ)——脂肪胺的电解氧化

本文用自旋捕捉技术与ESR相结合的方法研究了6种脂肪胺电解氧化过程中产生的瞬态自由基。结果表明,阳极上脂肪胺氧化产生相应的正离子自由基,而后脱去α-C上的质子得到一碳中心自由基,此自由基能被捕捉剂PBN所捕获;阴极上发生H~+还原反应,所得的氢原子也可被PBN捕获。     

抗坏血酸与过氧化氢反应的自旋捕捉-ESR研究

利用自旋捕捉-ESR方法研究了分析纯抗坏血酸(Aa)与医用维生素C注射液(Vc)的自氧化和过氧化氢反应,在自氧化反应中只观察到去氢抗坏血酸负离子基A-.,而与过氧化氢反应时除观察到A-.外,还观测到另外数种自由基,经计算机拟合后得到这些自由基或其5,5-二甲基-1-吡咯啉-1-氧化物(DMPO)加合物的ESR谱参数,在此基础上推测出该反应的机理.     

自旋捕捉技术在Ph3M(M=N,P, As,Sb, Bi)光解反应中的应用

本文用自旋捕捉技术、柱色谱与ESR波谱相结合的方法, 研究了Ph_3M(M=N, P, As, Sb, Bi)光解过程的活泼自由基。从自旋捕捉剂亚硝基特丁烷(t-BuNO)、苯亚甲基叔丁基氮氧化合物(PBN)或2,3,4,6-四甲基亚硝基苯(ND)与活泼自由基形成的自旋加合物的ESR波谱的超精细结构, 确证这些化合物光解过程中有Ph·自由基存在。从而可推断它们的光解初级过程包括Ph_3M的均裂, 即Ph_3M→Ph_2M·+Ph·。此外,因Ph—M键能的大小顺序为
Pb—P>Ph—As>Pb—Sb>Ph—Bi
所以Ph_2M·(M=As, Sb, Bi)的分解比Ph_2P·容易, 实验中只检查出Ph_2P·, 则正是所预期的。     

自旋捕捉技术在Ph_3M(M=N,P,As,Sb,Bi)光解反应中的应用

本文用自旋捕捉技术、柱色谱与ESR波谱相结合的方法,研究了Ph_3M(M=N、P,As,Sb,Bi)光解过程的活泼自由基。从自旋捕捉剂亚硝基特丁烷 (t-BuNO)、苯亚甲基叔丁基氮氧化合物(PBN)或2,3,4,6-四甲基亚硝基苯(ND)与活泼自由基形成的自旋加合物的ESR波谱的超精细结构,确证这些化合物光解过程中有Ph·自由基存在。从而可推断它们的光解初级过程包括Ph_3M的均裂,即Ph_3M→Ph_2M·+Ph·。此外,因Ph—M键能的大小顺序为 Pb—P>Ph—As>Pb—Sb>Ph—Bi所以Ph_2M·(M=As,Sb,Bi)的分解比Ph_2P·容易,实验中只检查出Ph_2P·,则正是所预期的。     

过硫酸盐和脂肪环胺体系引发机理的ESR研究

用ESR方法研究了过硫酸盐和脂肪环胺吗啉,哌啶及其N-烷基取代衍生物体系引发反应的初级自由基,结合端基分析,证实了这类脂肪环胺与过硫酸盐反应产生的初级自由基都能引发烯类单体聚合。当所用的是脂环仲胺时,其初级自由基为氮中心自由基;用脂环叔胺时,初级自由基是N-烷基的α-碳中心自由基。     

芳基重氮盐及其冠醚络合物光解活泼自由基的ESR研究

本文用自由基捕捉剂2,3,5,6-四甲基亚硝基苯(ND)及苯亚甲基叔丁基氮氧化物(PBN)与ESR相结合的方法研究了芳基重氮盐RC_6H_4N~+_2BF~-_4(R=F, Cl, Br, I, NO_2, COOH,OCH_3及H)及其与18-冠-6、二苯并-24-冠-8的络合物在苯中的光解过程。结果表明它们光解产生了活泼自由基RC_6H_4并可被ND及PBN捕捉....     

An electron spin resonance study of radicals from chloramine-t-1 : Spin trapping of radicals produced in acid media

Under acid conditions aqueous solutions of chloramine-T form nitrogen-centred radicals via loss of the chlorine atom. The nitrogen radicals produced have been studied by ESR spectroscopy using the spintrapping method. Adducts of the spin trap phenyl-t-butyl nitrone are oxidized by chloramine-T in acid media to give a paramagnetic product in which the unpaired electron interacts with two inequivalent nitrogen atoms. The spin trap 5,5-dimethyl-2-pyrrolidine-1 -oxide is oxidized rapidly to 5,5-dimethyl-2-pyrrolidone-1-oxyl by chloramine-T under acid onditions. The water soluble trap α-4-pyridyl-1-oxide-N-t-butyl nitrone forms a stable nitroxide adduct with a nitrogen radical of chloramine-T in acid solution. Identical results were obtained with chloramine-B (sodium salt of N-chlorobenzene sulfonamide), indicating the involvement of the N-chloramine group in radical formation.     

脂族酰基过氧化物分解动力学的研究X: 过氧化酰热分解反应的自旋捕获ESR研究

用亚硝基丁烷(TNB)、亚硝基苯和C-苯基-N-叔丁基硝酮作为自旋捕获剂来捕获和检出一些二酰基过氧化物类化合物分解时形成的短命烷基自由基. 报导了烷基自由基对自旋捕获剂加成的氮氧化物自由基的电子自旋共振谱, 并观察到2,4,4-三甲基戊基自由基中α-CH2的氢是非对映和非等价的. 据此, 认为与这一类自由基的加合物产生的电子自旋共振谱与其它类型自由基是不同的.     

Direct ESR detection and spin trapping of radicals generated by reaction of oxygen radicals with sulfonated poly(ether ether ketone) (SPEEK) membranes

The stability of membranes under the strong oxidizing conditions in fuel cells is one of the major challenges in the development of fuel cells based on proton exchange membranes (PEMs). This study is centered on the determination of the susceptibility to degradation of SPEEK membranes exposed to OH radicals, using both direct ESR and spin trapping with 5,5-dimethyl-1-pyrroline-1-oxide (DMPO). In order to achieve a complete picture on SPEEK degradation, two types of experiments were performed: 1. UV irradiation at 77 K of SPEEK membranes swollen by aqueous solutions of H₂O₂; 2. UV irradiation of SPEEK membranes swollen by aqueous solutions of H₂O₂ in the presence of DMPO as a spin trap. UV irradiation without oxygen of SPEEK at 77 K in acid or basic form in the presence of H₂O₂/H₂O produced phenoxyl radicals as the predominant radicals detected by direct ESR or spin trapping methods. At pH 4, the oxygen radicals produced phenyl radicals as the predominant species detected by spin trapping methods. The hydroperoxyl radical, as DMPO/OOH adduct, was detected only when the DMPO/OH adduct was absent. The appearance of phenyl and phenoxyl radicals provides the evidence that OH radicals react with the aromatic ring of SPEEK or leading to the scission of its ether bridge.     

毛细管柱GC/MS/ESR 联用研究自由基PBN加合物

采用硅烷化方法，并用石英毛细管柱气相色谱与双聚焦质谱仪组成的ＧＣ／ＭＳ联用系统，首次成功地分析鉴别了六种自由基的ＰＢＮ加合物，总结了这些自旋加合物的断裂规律。实验结果表明，硅烷化结合ＧＣ／ＭＳ和自旋捕捉ＥＳＲ联用技术是确定活泼自由基的一种有效方法。     

A Novel and Convenient Assay for the Determination of OH Produced by Fenton Reaction

Oxygenradicalsaswellas0theroxygen-derivedspeciesincludinglipidperoxides,havebeensuggestCdaspotentiallyimportantcausativeagents0fagingandvarioushumandi,...,i-3suchascancer,multiplescler0sis,Parkinson'sdisease,autoinununediseases,ischemia,anemia,seniledementiaandasbestosis.Am0ngthevari0usradicals,thehydroxylradical(OH)ispresumedtoplayacentralroleduetoitSstr0ngactivity'.TheimPortanceofremovingexcessiveactiveoxygenspeciesfromlivingorganismsisbecondngincreasinglyrec0gnized,t0getherwithagrowingint…     

ESR investigation of the oxidative damage in lungs caused by asbestos and air pollution particles

Exposure to asbestos and air pollution particles can be associated with increased human morbidity and mortality. However, the molecular mechanism of lung injuries remains unknown. It has been postulated that the in vivo toxicity results from the catalysis of free radical generation. Using electron spin resonance (ESR) in conjunction with the spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) we previously investigated in vivo free radical production by rats treated with intratracheal instillation of asbestos (crocidolite fibers) and an emission source air pollution particle (oil fly ash). In this report we compare the effect of two different exposures on the type of free radicals they induce in in vivo animal model. Twenty-four hours after the exposure, ESR spectroscopy of the chloroform extract from lungs of animals exposed to either asbestos or oil fly ash gave a spectrum consistent with a carbon-centered radical adduct (aN = 15.01 G and aH = 2.46 G). To test whether free radical formation occurred in vivo and not in vitro, a number of control experiments were performed. Combinations (both individually and together) of asbestos or oil fly ash and 4-POBN were added to lung homogenate of unexposed rats prior to chloroform extraction. No detectable ESR signal resulted. To exclude the possibility of ex vivo free radical generation, asbestos or oil fly ash was added to lung homogenate of an animal treated with 4-POBN. Also, 4-POBN was added to lung homogenate from rats instilled with asbestos or oil fly ash. Neither system produced radical adducts, indicating that the ESR signal detected in the lung extracts of the treated animals must be produced in vivo and not ex vivo or in vitro. In conclusion, ESR analysis of lung tissue demonstrated that both exposures produce lipid-derived radical metabolites despite their different composition and structure. Analogously, both exposures provide evidence of in vivo enhanced lipid peroxidation. Furthermore, it is concluded that without the presence of a spin-trapping agent, no free radical metabolites could be detected directly by ESR in either exposure.