皮秒级脉冲辐解装置及其在抗氧化剂研究中的应用

20世纪60代出现了微秒级脉冲辐解技术，开始了快速反应动力学的研究。其重要发现之一是溶剂化电子，它证实了人们早先的推测，并极大地促进了化学反应机理研究。随着加速器与电子学技术的发展，随后出现了纳秒、皮秒与飞秒级脉冲辐解装置。虽然纳秒时间分辨仍然是研究凝聚态化学反应机理的有效的手段，但在观察更快的化学反应和过程时，如超激发态、分子分裂和分子内电荷传递等过程，     

皮秒级脉冲辐解装置及其在抗氧化剂研究的应用

20世纪60代出现了微秒级脉冲辐解技术,开始了快速反应动力学的研究.其重要发现之一是溶剂化电子,它证实了人们早先的推测,并极大地促进了化学反应机理研究.随着加速器与电子学技术的发展,随后出现了纳秒、皮秒与飞秒级脉冲辐解装置.虽然纳秒时间分辨仍然是研究凝聚态化学反应机理的有效的手段,但在观察更快的化学反应和过程时,如超激发态、分子分裂和分子内电荷传递等过程,必须借助更快的时间分辨研究.我所于1990年建立了我国第一个纳秒级电子脉冲辐解装置,基于加速器技术与动态化学研究的良好基础,我所正在研制皮秒脉冲电子束装置,以将我国的脉冲辐解时间分辨研究推进到皮秒级水平,推动我国在自由基生物学、环境科学、高分子材料科学等领域的相关研究.生物体在呼吸和代谢过程都会产生活性氧自由基(ROS),同时电离辐射、紫外线及致癌物质等也会通过直接或间接作用产生活性氧自由基.体内一定浓度的自由基是机体进行正常生命活动的必要条件之一.但过多的自由基,会攻击生物膜的不饱和脂肪酸,引起膜脂质过氧化反应;或攻击蛋白质引起其结构与构象的改变,造成肽链断裂、聚合与交联;或攻击DNA,造成其永久性损伤.这些生物大分子结构与功能的改变,导致细胞功能的紊乱,导致细胞的衰老、畸变及死亡,是心脑血管疾病及癌症的祸首.随着人体年龄的增加,体内修复酶的活性不断下降,细胞中DNA氧化性损伤增多,受损伤的DNA不断积累,使人体患癌症的可能迅速上升(研究表明,癌症的发病率与年龄的4次方成正比).天然抗氧化剂是一类单电子氧化还原电位很低的活性物质,可清除活性氧自由基,又可通过电荷转移反应修复被氧化的DNA碱基及脂质过氧自由基等,因而是防止活性氧自由基对生物体损伤的有力措施.以往的研究表明,茶多酚、维生素C等天然抗氧化剂对心脑血管疾病等具有预防和保护作用.我们利用纳秒级脉冲辐解装置对抗氧化剂进行了研究(1)研究抗氧化剂与各种氧化性自由基[1,2].(2)研究抗氧化剂对受损伤的DNA及其碱基的修复过程[3].揭示了抗氧化剂不仅可以通过竞争反应清除体内有害自由基,而且可以对已受损伤的生物分子进行快速修复,减轻有害自由基对生物体的损伤.(3)研究抗氧化剂对受损伤的蛋白质及其氨基酸自由基的修复过程.这些研究为更好地了解和解释抗氧化剂在生物体内的作用机理提供了理论基础,也为开展其皮秒级脉冲辐解研究奠定了基础.     

甲基肼水溶液的脉冲辐解研究

利用脉冲电子束进行甲基肼水溶液的脉冲辐解研究,对其瞬态光谱中的主要吸收峰作了归属,并初步考察了这些瞬态物种的生长、衰减等行为.结果表明,·OH与甲基肼反应生成CH3·NNH2,速率常数为(2.4±0.1)×1010mol-1·L·s-1;enq-与甲基肼反应生成CH3·NHNH2自由基,速率常数为(2.7±0.2)×1...     

二甲基羟胺水溶液的脉冲辐解研究

利用脉冲电子束进行二甲基羟胺(DMHAN)水溶液的脉冲辐解研究,对其瞬态光谱中的主要吸收峰作了归属,并初步考察了这些瞬态物种的生长、衰减等行为。研究结果表明,·OH与DMHAN反应生成(CH3)2NO·自由基,测得速率常数为(4.5±0.3)×109mol-1·L·s-1;eaq-与DMHAN反应生成(CH3)2N·自由基,测得速率常数为(1.3±0.04)×109mol-1·L·s-1。     

脉冲辐解研究 DNA 羟基加成自由基快速修复过程

脉冲辐解研究ＤＮＡ羟基加成自由基快速修复过程⒇姜岳姚思德林念芸（中国科学院辐射化学开放研究实验室中国科学院上海原子核研究所上海２０１８００）氧自由基由于具有极其活泼的化学活性和致癌、致心血管疾病、感染及促进衰老等作用而引起人们的广泛关注。而羟自由基氧...     

苯胺的脉冲辐解和激光光解研究

用脉冲辐解与激光光解时间分辨技术,从瞬态方面研究了苯胺Photo-Fenton降解的可行性。研究表明,水溶液中苯胺可为308nm的激光光电离,光电离的瞬态产物为阳离子自由基及脱质子后的中性自由基;并测得阳离子自由基脱质子转变为中性自由基的pKa值为7．5,以二苯甲酮为参比,测得苯胺光分解的量子产额极高（0．08）。应用脉冲辐解时间分辨技术研究了苯胺被羟基自由基降解的反应机理,结果表明,36％的羟基自由基直拉进攻－NH2形成苯胺,54％的羟基自由基与苯胺邻位加成,10％的羟基自由基与苯胺对位加成。     

氨基羟基脲脉冲辐解研究

研究了脉冲辐解过程中氨基羟基脲与水辐解活性粒子（e^-_aq、·OH和·H）及单电子氧化剂·CO₃^-的反应动力学过程。反应近似为准一级反应,反应速率常数分别为k（e^-aq）=1.41×10⁸ L/(mol·s)、k（·OH）=1.05×10¹⁰ L/(mol·s)、k（·H）=2.68×10⁵ L/(mol·s)、k（·CO^-₃）=4.25×10⁸ L/(mol·s)。其中氨基羟基脲与·OH的反应速率常数最大,故在辐解过程中其为主要反应。     

2-氯酚水溶液的脉冲辐解研究

利用脉冲辐解技术对 2-氯酚水溶液在多种条件下的降解行为进行了详细研究。对瞬态光谱中的主要吸收作了归属,并考察了这些瞬态产物的生成和衰减动力学。研究表明,在不同 pH 值下,2-氯酚与?OH 的反应途径不同:中性条件下主要生成羟基加成物,其生成速率常数为 8.3×109dm3?mol-1?s-1;碱性条件下,则主要发生电子转移形成 2-氯代酚氧基,同时存在羟基加成物脱 HCl 和脱 OH-过程。?N3与 2-氯酚发生单电子氧化,形成 2-氯代酚氧基。?H 与 2-氯酚发生加成反应生成环己二烯类氢加成物,其速率常数为 2.5×109dm3 ? mol-1 ? s-1。eaq 与 2-氯酚发生电子转移,生成羟苯基和氯离子,碱性条件(pH=11)和中性条件下的速率 -常数分别为 3.5×108 dm3?mol-1?s-1和 2.2×109 dm3?mol-1?s-1。该结果有助于人们进一步了解氯酚降解的本质,从而为该类化合物的降解处理提供了理论基础。     

环境雌激素己烯雌酚的流动池脉冲辐解瞬态谱

己烯雌酚(DES)是一种活泼的环境雌激素。利用流动池脉冲辐解手段对其活性瞬态粒子的动力学特性作了初步研究，发现己烯雌酚自由基的苯环间双键可能是羟自由基优先进攻破坏的一个位点。该化合物对高能电子束非常敏感，通过自由基机理被降解。研究结果对DES环境降解机理和生物毒理，对探索解毒、环境修复等，具有一定的指导意义。     

早稻田大学皮秒脉冲辐解装置

A compact pulse radiolysis apparatus using a BNL-type s-band photocathode RF gun is now under development at Waseda University. The laser pulse is used for excitation of the photocathode and for generation of white light, which is used for analyzing light in the pulse radiolysis.The system design is shown in Fig. 1. For absorption spectroscopy with wide wavelength region, the white-light continuum was used as analyzing light. The white light continuum was generated by focusing the high intense IR laser into the water cell. The available wavelength was 400-950 nm. Typical data obtained is shown in Fig.2 by using the system. We have performed a deconvolution technique to know the time resolution of our system. For this purpose, we have assumed the shapes of the electron pulse and the laser pulse as Gaussian distributions. Furthermore, the difference of velocity in a sample cell between the electron pulse and the laser pulse due to the refractive index of a sample was also taken into consideration and assuming that the hydrated electrons are formed as a step function and the response function is Gaussian.Thus, time resolution of the system was estimated by deconvolution of the experimental data.We have achieved a time resolution of about 26ps by measuring time profile of hydrated electrons in H2O.     

喹啉及其衍生物的脉冲辐解和激光光解研究

Quinoline and some of its derivatives were reported to be carcinogenic, toxic and mutagenic. The widespread use of quinoline and its derivatives entails that these compounds are distributed in the environment, polluting soil and water together with many other environmental chemicals.     

Study of proton radiolysis of solid uracil film

In order to understand the molecules mechanism of ion irradiation,which has been widely used in many fields such as cancer therapy,uracil,one of the bases of nucleic acid.was chosen in the low energy ion radiolysis research.The solid uracil films with mass thickness of 0.314mg/cm^2 were irradiated by 200keV H^ ions .The experimental results show that 200keV H^ ions are effective in decomposition of uracil molecules.One of the decomposition products,5,6-dihydro-uracil,was separated by high performance liquid chromatograph (HPLC) and detected using an UV-light detector.Its yield increases first but then decreases as the ion dose increasing.In addition,the mechanism of uracil decomposition and 5,6-dihydro-uracil formation was also disucssed.     

数字式随机脉冲产生器

介绍了一种时间间隔服从指数分布的随机脉冲的产生方法 ,并加以实现 ;用查表法产生服从指数分布的随机数 ,用 80 31单片机制作了一台可编程脉冲产生器 ,可用于产生周期或随机性脉冲 ,周期脉冲范围 10 0～ 9.999× 10 6 Hz,随机脉冲范围为 2～ 10 4Hz。     

Pulse radiolysis study on aqueous solution of nicotine

Nicotine has been studied for the first time by pulse radiolysis techniques. It has been found that hydrated electrons, hydrogen radicals and hydroxyl radicals can react with nicotine to produce anion radicals and neutral radicals, respectively, and the related rate constants have been determined.     

吲哚荷尔蒙自由基脉冲辐解光谱及其酸基平衡和还原电位性质研究

The Absorption spectral, acid-base equilibrium potential properties and formation and decay kinetics of four kinds of radicals from natural existing indole hormones were studied by pulse radiolysis.One of the most important properties for these four indolyl hormones, melatonin, 5-methoxygramine (MTA),5-methoxy-N, N-dimethylthytrytamine (DMM TA) and 5-methoxy-N, N-diethylthytrytamine (DEMT A), which are involved in biochemical processes and play crucial roles in many neuropathy and cancer related diseases, is their facile one electron oxidation with formation of radical cations or their conjugated base, the indolyl radicals.Formation kinetics and properties of the radicals were investigated by pulse radiolysis using the Linac accelerator with fast time-resolving optical system in UTNL.In the present study, these radicals were generated through oxidation of the corresponding hormone with azide radical in radiation induced process. Their spectroscopic properties were investigated and it was found that the transient spectra in all these cases exhibit similar absorption and pH dependence: in acidic solution, the radicals are characterized with three absorption maxima around 320-350, 440-460, 520-550nm. The spectra of MTA at various pH were shown as an example. From the absorption changes as a function of pH, two pK values were determined to be around 5 and 9 for the indolyl radicals except for melatonin, in which, only one pK was distinguished to be 4.4. Formation kinetics of the radicals was measured by following the growth of their absorption peaks and it was found that these indolyl derivatives transfer an electron to N3, with different rate constants, i.e.1.2×1010, 4.5×109, 4.9×109, 1.6×109 dm3 mol-1 s-1 for melatonin, MTA, DMMTA, and DEMTA, respectively.Reduction potentials of the radicals vs their molecules were also determined and they are dependent on the pH of medium. At pH 7, the reduction potentials were estimated to be 1.10, 1.18, 1.18, 1.20eV for melatonin, MTA,DMMTA and DEMTA, respectively. Because of its relatively high contents in human brain cells, melatonin is the main antioxidant among hormones against the oxidizing species in brain cells.     

Kinetics study of the solvated electron decay in THF using laser-synchronised picosecond electron pulse

Picosecond pulse radiolysis of neat tetrahydrofuran （THF） shows a fast decay of the solvated electron within 2.5ns. The decay of the solvated electron observed at 790nm is because of spur reaction. A numerical simulation using time dependent Smoluchowski equation containing a sink term with a distance dependent reaction rate is used to fit the pulse-probe data and shows that the geminate reaction can proceed at long distance in this low polar solvent.     

水相中喹啉的辐解机理研究

利用纳秒级脉冲辐解技术对多种条件下喹啉水溶液的氧化还原机理进行了研究,并对瞬态粒子的主要吸收峰作了归属。探讨了喹啉在羟基、氢自由基、水合电子作用下所产生的瞬态粒子的生成、衰减行为。研究表明,·OH与喹啉在碱性条件下反应生成OH-加合物,速率常数为5.5×109L/mol?s?;在酸性条件下喹11啉先与氢离子反应生成喹啉阳离子,再与羟基发生加成反应,反应速率常数为7.9×109L/mol?s?;在中性条11件下和在碱性条件下反应相似,反应速率常数为7.2×109L/mol?s?;喹啉与水合电子反应生成的喹啉阴离子11自由基,其反应速率常数为7.05×109L/mol?s?;喹啉还可以与氢自由基的发生亲电加成反应。11