链接琥珀酰亚胺的线性硝酮的合成与ESR研究

该文设计并合成一种新的线性硝酮自由基捕获探针DSC-PBN(N-(4-(((2,5-dioxopy-rrolidin-1-yloxy)-carbonyloxy)methyl)benzylidene)-2-methylpropan-2-N-oxide),并采用UV、MS、1H NMR等一系列手段表征分子结构.进一步通过自由基捕获实验显示,DSC-PBN可与多种活泼自由基反应生成稳定的氮氧自由基加合物,且所得ESR谱图易于解析和分辨.由于DSC-PBN自由基捕获探针链接琥珀酰亚胺基团,可望通过与蛋白质(或多肽)N端的共价键合而应用于生物体系自由基分析.     

卷烟烟气中活性自由基的自旋捕获ESR研究

卷烟烟气中的瞬态自由基对人体健康是相当有害的，而检测活性自由基最常用的方法是自旋捕获方法. 本研究中使用高效新型捕捉剂DEPMPO能够直接在水相中捕捉到烷基自由基与羟基自由基，并未发现烷氧自由基加合物. 考虑到DEPMPO对活性自由基的捕捉能力和加合物ESR谱图解析特征性都优于PBN与DMPO，且在有机溶剂中溶解较多的氧分子. 因此认为以往文献中所捕获的烷氧自由基来源于烷基自由基氧化后的次级自由基产物.     

配合物PdCl2[(PPh2)2CHCl]的合成、结构及反应机理

合成了新配合物PdCl₂[(PPh₂)₂CHCl],用核磁、红外光谱、元素分析等表征了其结构,X-rax衍射确定了单晶结构.应用电子顺磁共振-自旋捕获(EPR-ST)对技术研究了其反应的机理.捕获到PPh₂及含碳自由基中间体,提出了反应机理.     

配合物PdCl_2[(PPh_2)_2CHC1]的合成、结构及反应机理

合成了新配合物PdCl2[(PPh2)CHCl]，用核磁、红外光谱、元素分析等表征了其结构，X－rax衍射确定了单晶结构.应用电子顺磁共振-自旋捕获（EPR－ST）对技术研究了其反应的机理．捕获到PPh2及含碳自由基中间体，提出了反应机理．     

Pd(OAc)_2与有机双膦在氯代烷中的反应机理(Ⅱ)研究

在前文[1 ,2 ] 基础上 ,扩展了有机双膦系列 .应用电子自旋捕获技术 (EPR ST)研究了Pd(OAc) 2 与系列有机双膦dppm(二 (二苯基膦甲烷 ) )、dppe(二 (二苯基膦乙烷 ) )及dppp(二(二苯基膦丙烷 ) )在氯代烷中反应的反应机理 ,所用捕获剂为PBN ,得到EPR实验谱并进行了模拟 .提出了反应机理并进行了讨论 .并对影响反应的一些因素进行了探讨 .Pd(OAc) 2 在此反应中既是反应物又是引发剂 ,在反应中起分子诱导作用 .当Pd(OAc) 2 与非自由基物种有机双膦配体及氯代烷共存时 ,引发了自由基反应 .     

Pd(OAc)2与PPh3在氯代甲烷中的反应研究

用Pd(OAc)₂与PPh₃在四氯甲烷中反应,合成了配合物PdCl₂(PPh₃)₂?CCl₄,得到单晶,用X-ray衍射确定了单晶结构.应用电子顺磁共振-自旋捕获(EPR-ST)技术研究了其反应的机理.捕获了含碳自由基中间体,提出了反应机理.     

发光自由基 老树发新芽

从提出自由基的双线态电致发光新机制,到成功实现高发光效率的自由基,再到开发具有可调控自旋态的发光双自由基,这一系列的创新为一个世纪前已存在的自由基领域重新注入了新的活力。本文追溯了稳定有机自由基的历史,并介绍了我们在发光自由基领域近期的研究进展。     

用荧光探针法研究茶叶花粉黄酮对氧自由基致鼠红细胞膜氧化损伤的保护作用

应用1,6-二苯基-1,3,5-已三烯(DPH)为荧光探针,超氧阴离子自由基和羟基自由基致鼠红细胞膜氧化损伤为模型,研究了茶叶花粉黄酮对鼠红细胞膜氧化损伤的影响.结果表明,超氧阴离子自由基和羟基自由基均能引起鼠红细胞膜脂质过氧化反应,脂质过氧化产物丙二醛含量显著升高,膜脂流动性下降.将鼠红细胞膜预先用茶叶花粉黄酮处理后,膜脂的MDA含量明显下降,呈现剂量与效应关系,膜脂流动性显著提高,表明茶叶花粉黄酮对超氧阴离子自由基和羟基自由基引起的鼠红细胞膜的氧化损伤有保护作用.     

Pd(OAc)2与有机双膦在氯代烷中的反应机理(Ⅱ)研究

在前文^[1,2]基础上,扩展了有机双膦系列.应用电子自旋捕获技术(EPR-ST)研究了Pd(OAc)₂与系列有机双膦dppm(二(二苯基膦甲烷))、dppe(二(二苯基膦乙烷))及dppp(二(二苯基膦丙烷))在氯代烷中反应的反应机理,所用捕获剂为PBN,得到EPR实验谱并进行了模拟.提出了反应机理并进行了讨论.并对影响反应的一些因素进行了探讨.Pd(OAc)₂在此反应中既是反应物又是引发剂,在反应中起分子诱导作用.当Pd(OAc)₂与非自由基物种有机双膦配体及氯代烷共存时,引发了自由基反应。     

检测活性氧的荧光探针新进展

活性氧对于人体是十分重要的。然而,过量的活性氧是相当有害的,它们会对人体产生氧化损伤,导致细胞死亡。活性氧现在已经引起了化学、生物、医药等多个领域学者的浓厚兴趣,它们被认为和多种病理条件有密切的联系。由于活性氧寿命短、反应活性高,并且大部分都存在于体内很难被捕获,因此它们的分析测定是一项国际性难题。荧光探针作为活性氧的高灵敏的检测分析物,已经得到越来越广泛和深入的研究。由于每一种活性氧都有它独特的生理学活性,因此设计高选择性的,能够检测具体一种活性氧的荧光探针分子就显得十分重要。本文主要对近三年来检测单线态氧、过氧化氢、超氧阴离子和羟自由基这四种活性氧的荧光探针的研究进展进行综述,关注这类荧光探针的检测机理以及具体应用。     

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.     

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.     

Diffusion,trapping and detrapping of positive muon in Al-0.047% Mg

Positive muon spin relaxation was measured in Al-0.047% Mg quenched from 873 K under zero external magnetic field from 6.3 K to 270 K. The observed spectra were analysed with the calculated muon spin relaxation function which included the static relaxation rates, the trapping rates, the detrapping rates and thet=0 initial trapping fractions. Due to the precise measurements and the realistic expression of spin relaxation function, above four parameters could be determined distinctly. The trapping rates and the distortions around a muon were determined from the values of static relaxation rates at a trapping site. The diffusion features were clearly described by the trapping and detrapping rates. The diffusion process was determined by the temperature dependence of these parameters.     

EPR study of the toxicological effects of gas-phase cigarette smoke and the protective effects of grape seed extract on the mitochondrial membrane

Electron paramagnetic resonance spin trapping and spin labeling techniques were used to study the effects of grape seed extract on the biophysical propertiers of the mitochondrial membrane exposed to gas-phase cigarette smoke. The spin trapping results indicated that grape seed extract can effectively scavenge free radicals in cigarette smoke and the lipid free radicals generated from the lipid peroxidation of mitochondrial membrane caused by gas-phase cigarette smoke. The spin labeling results showed that grape seed extract can protect the mitochondrial membrane from the toxicological damage caused by gas-phase cigarette smoke.     

Optical nuclear spin polarization in quantum dots

Hyperfine interaction between electron spin and randomly oriented nuclear spins is a key issue of electron coherence for quantum information/computation. We propose an efficient way to establish high polarization of nuclear spins and reduce the intrinsic nuclear spin fluctuations. Here, we polarize the nuclear spins in semiconductor quantum dot(QD) by the coherent population trapping(CPT) and the electric dipole spin resonance(EDSR) induced by optical fields and ac electric fields. By tuning the optical fields, we can obtain a powerful cooling background based on CPT for nuclear spin polarization. The EDSR can enhance the spin flip–flop rate which may increase the cooling efficiency. With the help of CPT and EDSR, an enhancement of 1300 times of the electron coherence time can be obtained after a 10-ns preparation time.     

Alkylperoxyl spin adducts of pyrroline‐N‐oxide spin traps: Experimental and theoretical CASSCF study of the unimolecular decomposition in organic solvent,potential applications in water

Spin trapping coupled with electron paramagnetic resonance spectroscopy is the most direct method for detection of very low concentrations of free radicals, and it has been intensively used to detect superoxide or alkylperoxyl radicals in biological systems, using cyclic nitrones as spin traps. The half‐life time of the ensuing spin adducts depends dramatically on the spin trap structure; however, their mechanism of decay has never been definitely established. We investigated at the MRMP2/CASSCF (MultiReference second‐order Møller‐Plesset perturbation theory/Complete Active Set Self Consistent Field) level of theory the mechanism of decay of methylperoxyl and tert‐butylperoxyl spin adducts formed with various cyclic nitrones. We showed that no transition state can be located for the O─O homolytic cleavage, which yields an intermediate biradical with the following sequence ^?O─N─C─O^?. Then, homolytic cleavage of the N─C bond yields a nitrosoaldehyde, through an early transition state with a very low activation energy. For each nitrone used as spin trap, electrospray ionization mass spectrometry analysis of the spin trapping mixture allowed to detect the presence of the expected nitrosoaldehyde. We generated tert‐butylperoxyl spin adducts in toluene, and we found a good correlation between their half‐life time and the bond dissociation energy of their peroxidic O─O bond. The theoretical method was then extended to hydroperoxyl spin adducts in water and provided promising results.     

An EPR Study of Superoxide Radicals from Potassium Superoxide Solutions

Electron paramagnetic resonance spectroscopy and the spin trapping technique were employed in order to monitor the superoxide radical liberated from potassium superoxide in aqueous alkaline solutions; DEPMPO (5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide) was used as a trapping agent. Three reaction systems were prepared, varying the ratios between KO₂, superoxide and DEPMPO. The data indicate distinct mechanisms leading to DEPMPO/spin adducts with different kinetic rates.     

Recent applications of EPR and spin trapping to sonochemical studies of organic liquids and aqueous solutions

In this paper we review some of our recent applications of the EPR spin trapping technique to sonochemical studies which include identification of radicals formed in organic liquids and aqueous mixtures of organic liquids, estimation of temperatures of sonochemical regions in mixtures of deuterated and non-deuterated solvents, and the identification of reactive radical intermediates which may play a role in synergistic cell killing by ultrasound and drugs (sonodynamic interactions).     

Effective field theory for spinor dipolar Bose Einstein condensates

We show that the effective theory of long wavelength low energy behavior of a dipolar Bose-Einstein condensate(BEC) with large dipole moments (treated as a classical spin) can be modeled using an extended non-linear sigma model (NLSM) like energy functional with an additional non-local term that represents long ranged anisotropic dipole-dipole interaction. Minimizing this effective energy functional we calculate the density and spin-profile of the dipolar Bose-Einstein condensate in the mean-field regime for various trapping geometries. The resulting configurations show strong intertwining between the spin and mass density of the condensate, transfer between spin and orbital angular momentum in the form of Einstein-de Hass effect, and novel topological properties. We have also described the theoretical framework in which the collective excitations around these mean field solutions can be studied and discuss some examples qualitatively.