光解杜醌/氢给体均相体系的CIDEP研究

以杜醌为光敏剂,用高时间分辨电子自旋共振 (TRESR)波谱仪研究了杜醌/乙二醇体系、杜醌/氮氧自由基/乙二醇体系的化学诱导动态电子自旋极化(CIDEP).实验表明,紫外激光照射下,在杜醌/乙二醇溶液中得到以三重态机理极化为主的中性杜半醌自由基DQH*和以碳为中心的乙二醇碳自由基R*(OH)2的极化信号,而加入氮氧自由基 TEMPO后,则只观测到极化的TEMPO的E+E/A极化谱,其产生机理属于以四重态为先驱的自由基-三重态对极化机理(QP-RTPM),结合极化强度的理论计算对该体系的极化形成过程进行了分析.     

痂囊腔菌素A的生物合成和光化学反应研究

报道了从中国云南西部山区筛选到一株丝状真菌Ascomyceters Hypocreaceae Hypomyces (Fr.) Ful SP.，并在实验室成功地进行培养. 这株真菌代谢产物的化学组分是痂囊腔菌A（EA），并经紫外光谱、元素分析、MS、¹H NMR、¹³C NMR和X-衍射鉴定. 在适当的条件下将痂囊腔菌素A（EA）氯仿溶液和二苄胺（DBA）氯仿溶液混合. 用可见光照射混合液，在Varian E-115ESR仪上可以得到强吸收. 得到的数据表明，EA可以诱导DBA转变成氧氮自由基.     

杜醌自由基光化学路径的CIDEP研究

用自制的高时间分辨电子自旋共振波谱仪,测量得到了酸性、碱性和胶束环境下的光解杜醌/乙二醇(DQ/EG)溶液瞬态自由基的化学诱导动态电子自旋极化(CIDEP)谱.在光解均相DQ/EG溶液时,观察到了以增强发射的的中性杜半醌自由基(DQH.)的CIDEP信号;在碱性环境下(pH=9)和TX-100胶束环境下光解DQ/EG体系时得到杜醌负离子自由基(DQ-.)的CIDEP信号;在酸性环境下(pH=2.5)光解DQ/EG体系时,出现的又是中性杜半醌自由基(DQH.)的CIDEP信号.实验结果显示,DQH.由3DQ*与EG之间的氢原子转移反应生成,DQ.-由DQH.的去质子化反应生成,反应中伴随着极化转移.     

乙腈-水和乙二醇-水均相溶液中光诱导杜醌激发三重态与色氨酸、酪氨酸的氢原子转移反应（英文）

本文用激光闪光光解技术研究了光诱导生物醌杜醌激发三重态(~3DQ~*)和色氨酸(Trp)与酪氨酸(Tyr)在乙腈-水(MeCNH_2O)及乙二醇-水(EG-H_2O)均相溶液中的光化学反应,分析了反应的机理,并基于Stern-Volmer方法测量了反应速率常数.光解DQ体系可以生成~3DQ~*,3DQ~*与Trp、Tyr发生的氢原子转移反应占主导地位.对于DQ/Trp/MeCN-H_2O和DQ/Trp/EG-H_2O溶液,3DQ~*与Trp反应生成杜醌中性自由基DQH·、以碳为中心的色氨酸中性自由基Trp/NH和以氮为中心的色氨酸中性自由基Trp/N·.对于DQ/Tyr/MeCN-H_2O和DQ/Tyr/EG-H_2O溶液,3DQ~*与Tyr反应生成DQH·和酪氨酸中性自由基Tyr/O·.~3DQ~*与Trp、Tyr的氢原子转移反应速率常数都在10~9 L·mol~(-1)·s~(-1)量级,反应近似受扩散控制.MeCN/H_2O均相溶液中~3DQ~*与Trp、Tyr的反应速率常数要明显高于EG/H_2O均相溶液中的反应速率常数,这与Stokes-Einstein方程定性一致.     

苯并呋咱-1-氧化物与二级胺光化学反应的电子自旋共振研究

本文报道了二苯胺、甲基苯基胺、甲潜苄胺、二苄胺、二异丙胺和二乙胺分别与苯并呋咱-1-氧化物在紫外光照下发生光化学反应的电子自旋共振(ESR)研究结果。结果表明:紫外光的作用首先使苯并呋咱-1-氧化物处于激发态,它与二胺作用生成激基态络合物,经氧转移和二胺的氮氢键断裂而最终生成相应的氮氧自由基。     

入射激波诱导环氧丙烷爆炸特征研究

用自行设计激波管点火测试技术,实验研究了温度范围760-1380K间入射激波诱导下环氧丙烷的点火机理。利用激波管压力传感器测定了H*(486.1) 和O (470.5nm)随激波诱导强度变化的点火时间特征。实验结果表明：在低马赫数下氢氧自由基出现时间较接近,1.5-2.5马赫间随激波诱导强度增大而线性减小;而马赫大于2.5后,氧自由基的出现时间迅速减小,是由于高活化能的氧自由基的点火时间对强激波较敏感,而诱导强度大于3.5马赫后对两者点火影响区别就下明显了。实验数据将有益于含能材料点火时间的研究。     

入射激波诱导环氧丙烷爆炸特征研究

用自行设计激波管点火测试技术,实验研究了温度范围760-1380K间入射激波诱导下环氧丙烷的点火机理。利用激波管压力传感器测定了H*(486.1) 和O (470.5nm)随激波诱导强度变化的点火时间特征。实验结果表明：在低马赫数下氢氧自由基出现时间较接近,1.5-2.5马赫间随激波诱导强度增大而线性减小;而马赫大于2.5后,氧自由基的出现时间迅速减小,是由于高活化能的氧自由基的点火时间对强激波较敏感,而诱导强度大于3.5马赫后对两者点火影响区别就下明显了。实验数据将有益于含能材料点火时间的研究。     

菁染料光敏化超氧自由基的产生

本文用自旋捕捉技术研究了青染料在含氧的二甲基亚用溶液中将氧光还原成超氧自由基的反应,在水溶液中光照时产生的羟基自由基来源于是初形成的O₂^·。超氧负离子的形成是由于电子从激发态染料转移至溶解的氧,各种染料的光致ESR信号强度与染料的氧化还原电位有关。     

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.     

苯并氮杂冠醚结构与溶剂效应及某些其它性质的核磁共振研究

本文记取并归属了二十一种以前未见文献报道的N-取代苯并氮杂冠醚化合物在氯仿中的¹H和¹³C NMR谱,提供了一批原始数据。讨论了这批化合物中氮原子上取代基对于其¹H和¹³C NMR行为的影响以及(胺类)苯并氮杂冠醚化合物在溶液中的构象转动问题。按其不同的NMR待性将这批新合成的化合物分成酰胺类苯并氮杂冠醚化合物(Ⅰ系列)和胺类苯并氮杂冠醚化合物(Ⅱ系列)两个系列(见图);并确认Ⅱ系列化合物在氯仿中都有所谓"稀释位移效应",而Ⅰ系列化合物在同样的条件下不发生稀释位移效应。     

Evidence against singlet oxygen formation by sonolysis of aqueous oxygen-saturated solutions of Hematoporphyrin and rose bengal. The mechanism of sonodynamic therapy

The possible role of singlet oxygen in the mechanism of sonodynamic therapy, the synergistic effect of ultrasound and certain sonosensitizers, was investigated. We used 4,4'-bis(1-p-carboxyphenyl-3- methyl-5-hydroxyl)-pyrazole (DRD 156), a sensitive new reagent which reacts specifically with singlet oxygen (1O2) but not with OH radicals, superoxide anion radicals or H2O2, to produce an EPR detectable signal. Sonolysis (48 kHz) of 90% D2O oxygen-saturated PBS solutions of Hematoporphyrin or Rose Bengal did not lead to the formation of detectable EPR signals of the semiquinone radical of DRD156. In contrast, the EPR signal of the semiquinone radical of DRD156 was observed during photoirradiation of Hematoporphyrin at 505 nm or of Rose Bengal at 544 nm. These results are inconsistent with a major role for singlet oxygen formation in the sonolysis of aqueous solutions of these compounds. An alternative mechanism for sonodynamic therapy involving peroxyl and alkoxyl radicals is discussed.     

甲基紫精与醇类间的光诱导电子转移及光催化反应的ESR研究

用ESR方法研究了甲基紫精(MV⁺⁺)与甲醇,乙醇及苄醇等之间的光诱导电子转移和光反应过程.结果发现,甲基紫精存在条件下,某些很稳定的醇类也可以发生光催化分解和光催化氧化的反应,甲基紫精在反应过程中起的是催化剂的作用在无氧条件下,MV⁺⁺/C₂H₅OH体系经UV光照10min后即可观察到很强的MV⁺离子基的信号,表明甲基紫精与乙醇分子之间发生了电子转移;当进行较长时间光辐照,则MV⁺离子基逐步消失而生成H原子和碳中心自由基。在通氧条件下进行光照时,则无MV⁺基信号而产生OOH基和碳中心自由基的信号.当体系中有一定量的水存在时,OOH基减弱而产生·OH基,且随着水量的增加,·OOH基的强度更为减弱直至消失,而同时羟基浓度则大大增加.另一个有趣而重要的现象是,对于MV⁺⁺/苄醇体系,在通氧条件下辐照时可给出很强的超氧阴离子基O₂^-的信号,而MV⁺⁺/甲醇体系可产生较弱的O₂^-信号.但是在无氧时甲基紫精的存在进行光辐照甲醇并不发生反应,而苄醇却可被甲基紫精光催化分解产生很强的苄氧基,羟甲基等自由基.本文详细地研究和讨论了甲基紫精与几种醇之间的光诱导电子转移和相应的均相光催化反应过程的机理.     

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.     

Effect of gold nanoparticle size on acoustic cavitation using chemical dosimetry method

When a liquid is irradiated with high intensities of ultrasound irradiation, acoustic cavitation occurs. Acoustic cavitation generates free radicals from the breakdown of water and other molecules. Cavitation can be fatal to cells and is utilized to destroy cancer tumors. The existence of particles in liquid provides nucleation sites for cavitation bubbles and leads to decrease the ultrasonic intensity threshold needed for cavitation onset. In the present investigation, the effect of gold nanoparticles with appropriate amount and size on the acoustic cavitation activity has been shown by determining hydroxyl radicals in terephthalic acid solutions containing 15, 20, 28 and 35 nm gold nanoparticles sizes by using 1 MHz low level ultrasound. The effect of sonication intensity in hydroxyl radical production was considered.The recorded fluorescence signal in terephthalic acid solutions containing gold nanoparticles was considerably higher than the terephthalic acid solutions without gold nanoparticles at different intensities of ultrasound irradiation. Also, the results showed that the recorded fluorescence signal intensity in terephthalic acid solution containing finer size of gold nanoparticles was lower than the terephthalic acid solutions containing larger size of gold nanoparticles. Acoustic cavitation in the presence of gold nanoparticles can be used as a way for improving therapeutic effects on the tumors.     

ESR-spin trapping study on the sonochemistry of liquids in the presence of oxygen. Evidence for the superoxide radical anion formation

The sonolysis of water and some organic liquids such as ethylene glycol, methanol and chloroform in the presence of oxygen, at 20 and 475 kHz ultrasound frequencies has been investigated by the ESR-spin trapping technique. 5,5-Dimethyl-1-pyrroline-N-oxide (DMPO), 3,3,5,5-tetramethylpyrroline-N-oxide (TMPO) and N-tert-butyl-alpha-phenyl nitrone (PBN) were able to trap superoxide radical anion, generated as the result of the sonication of the organic media. The addition of superoxide dismutase (SOD) resulted in a dramatic decrease of the ESR signal intensity of the superoxide radical adduct. In addition, the thermolysis of the liquids under ultrasound was shown by ESR detection of the spin adducts of the radicals formed by homolytic fragmentation. Occasionally, the nature of the detected spin adduct was dependent on the sonication time or on the frequency of the ultrasonic radiation. Experiments carried out in the presence of 2-methyl-2-nitrosopropane (MNP) resulted in the detection of radicals originating from thermal decomposition of the spin trap, showing its lability under ultrasonic radiation.     

ENDOR studies of alkyl substituted p-Benzosemiquinones in reversed micelles and in 2-propanol

Various substituted p-benzosemiquinone radical anions, inter alia ubisemiquinone and derivatives, have been investigated in 2-propanol and in reversed micelles by EPR and ENDOR spectroscopy. Unsymmetrical semiquinones, with respect to the oxygen atoms, experience remarkable hyperfine shifts depending on the medium. This effect even allows differentiation between stereoisomers. Immobilization of the semiquinone molecules at the water-surfactant interface in reversed micelles gives rise to pronounced asymmetric linewidth effects. In the case of 2-cyclohexyl-3-methyl-1,4-benzosemiquinones, mixtures of two species (conformers) have been observed.     

Ultrasonic enhancement of electrochemiluminescence from arylacetate electrooxidation

This paper describes the previously unreported electrogenerated chemiluminescence (ECL) from the electro-oxidation of several aryl carboxylates at a platinum flag electrode in aqueous, methanolic and acetonitrile solutions using tetramethylammonium hydroxides as a supporting electrolyte. In most cases electrochemiluminescence was markedly enhanced by simultaneous irradiation with ultrasound during electrolysis. Increase in electrochemiluminescence intensity with electrolysis current and carboxylate concentration was observed. Addition of a radical scavenger or purging of the solution with oxygen lowers ECL emission intensity. In contrast the presence of oxygen enhances the intensity of sonoluminescence, which is a concurrent but weaker process occurring under ultrasonic irradiation alone. Ring-substituted phenylacetates almost always produced less electrochemiluminescence than the unsubstituted parent molecule, though within the substituents studied chloro-substituted phenylacetates produced more ECL intensity than either methoxy- or nitro-substituted derivatives.     

Determination of absolute concentration of nitroxide radical by radio-frequency EPR imaging

The absolute concentrations of a nitroxide radical in samples in a loop-gap resonator (LGR) were determined by using a radio-frequency (about 720 MHz) electron paramagnetic resonance (EPR) imaging system. EPR imaging of phantoms containing a nitroxide radical, 3-carbamoyl-2,2,5,5-tetramethylpyrrolidin-1-yloxy (carbamoyl-PROXYL), dissolved in various concentrations of an aqueous sodium chloride solution was made to investigate the influence of dielectric losses and sample position within the LGR. As it was found that these influences on the signal intensity were sufficiently small (less than 6%), it is possible to use identical radical solutions in which the radical is dissolved in a known concentration as an internal marker. Two phantoms containing aqueous solutions of 3 mM (as a marker) and 1, 2, 3, 4, or 5 mM (as a sample) carbamoyl-PROXYL were placed together in the LGR. From EPR images of these phantoms, the absolute concentration of the sample could be calculated by using the gray-scale value (i.e., the signal intensity) of the marker and sample within a small margin of error (about 4%).