液态簧振动力学谱在蛋白质水凝胶脱水变性过程的应用研究

本文用液态簧振动力学谱(RMS-L)方法, 对典型蛋白质水凝胶鸡蛋清的脱水变性过程进行了测量, 结果表明, 随水含量的减少, 鸡蛋清至少存在4个力学谱的显著变化过程. 基于此结果并结合力学谱的理论分析, 作者推测, 随水含量的减少, 鸡蛋清可能依次存在下述4个状态: 1) 类体水(bulk-likewater) 的蛋白质水凝胶态; 2) 键合水 (bond water) 的蛋白质水凝胶态; 3) 键合水和键合蛋白质(bonding protein) 的混合态; 4) 键合蛋白质态. 而蛋白质的空间构型(spatial configuration)转变即变性, 主要发生在拥有键合水的蛋白质通过失水向键合蛋白质转变的混合态. 这表明RMS-L对鸡蛋清脱水变性过程的检测是有效的, 所得结果对蛋白质变性机理、以及蛋白质水凝胶态的深入研究也应具有参考价值. 关键词： 力学谱 蛋白质水凝胶 蛋白质变性     

Crystal melting processes of propylene carbonate and 1,3-propanediol investigated by the reed-vibration mechanical spectroscopy for liquids

The melting of crystals is one of the most common and general phase transition phenomena.However, the mechanism of crystal melting is not well understood, and more experimental measurements and explorations are still needed.The mechanical spectra of propylene carbonate and 1,3-propanediol during the crystal melting processes are measured by the reed vibration mechanical spectroscopy for liquids(RMS-L) for the first time.The experimental results show that as the temperature increases, the real part of the complex Young modulus first decreases slowly, and then quickly drops to zero;meanwhile, its imaginary part increases slowly at first, then goes up and drops quickly to zero, showing a peak of internal friction.Preliminary analyses indicate that both the real and imaginary parts can present some characteristics of the melting process, such as the transition from the disconnected liquid regions to the connected liquid regions, that from the connected crystal regions to the disconnected crystal regions, and so on.In addition, the results show that the melting rate per unit volume of crystalline phase versus temperature satisfies the Arrhenius relation at the initial stage of melting, and deviates from this relation as the temperature increases to a certain value.Therefore, the RMS-L will provide an effective supplement for the further study of melting.     

我国电子自旋共振波谱领域研究的50年回顾

电子自旋共振(ESR)波谱技术自1944年发现以来, 迄今已在化学、物理学、地矿学、生物学特别是生命科学的许多领域得到广泛应用, 由初期主要是对长寿命和稳定的顺磁粒子的研究, 逐步发展到对短寿命中间体, 反应过程机理和动力学的研究. 在检测技术方面, 日益广泛 地采用自旋标记, 自旋捕捉, 时间分辨ESR, 电子 核双共振, 化学诱导动态电子极化(CIDE P )和自旋回波等技术. 我国从20世纪50年代末开始将ESR技术用于某些研究领域, 80年代以后有了很快的发展. 以下仅就我国几十年来ESR研究领域的几个主要方面予以简单回顾. 有关文献引用只限于国内外核心刊物正式发表的论文和报道.     

ESR法研究龙胆酸在碱性溶液中的反应

本文用静态毛细管法研究了龙胆酸在醇钠-醇溶液中的反应,主要是氧化反应,发现了属于同一类型三种新的自由基物种,给出了它们的自由基结构模式;龙胆酸在氢氧化钠水溶液中的反应,不仅有氧化还有取代反应,氧化之后紧接着进行取代反应,本文都给予了解释。     

Process intensification using cavitation: optimization of oxidation conditions for synthesis of sulfone

Cavitation can be effectively used for intensification of chemical reactions due to the production of free radicals and conditions of high temperatures and pressures locally. In the present work, use of cavitation for the intensification of the synthesis of sulfone has been explored. The oxidation of thioether or sulfide to synthesize corresponding sulfone with 30% H₂O₂ as an oxidant was studied under acoustic cavitation and the results have been compared with the conventional approach based on the use of mechanical agitation. The aim has been also to optimize the different operating conditions viz. molar ratio of reactants to the oxidizing agent, type of the catalyst as well as its concentration, type of the solvent and the reactant concentration, so as to maximize the degree of intensification. It was observed that under the optimized conditions of sonication, the yield of sulfone was about five to six times higher as compared to the conventional approach of using mechanical agitation only.     

心肌缺血再灌过程中自由基生成动力学的ESR研究

采用自旋捕捉ESR方法研究了大白鼠和豚鼠在心肌缺血再灌注中自由基产生的动力学过程,首次测出复氧过程中羟基自由基变化的动力学曲线.同时结果还表明,在缺血后的复氧过程中除羟基·OH之外,还有碳中心自由基R·和可能的烷氧基RO·的生成,但其中·OH基生成的量经常是最大的.由于·OH基具有很高的反应活性,因而不可避免地就会通过它的夺氢作用导致碳中心自由基R的生成.特别有趣的是,羟基产生过程中其ESR信号的强度总是随着时间不断地增强而达到一最大值,然后又逐步地缓慢衰减到趋于几乎消失,此现象迄今尚未见有文献报道.我们建立了可近似表征羟基自由基生成速度的上升和下降过程的动力学方程.自由基生成与变化过程亦可近似地用退化分支链反应图式来予以描述.在所提出的链反应过程图式中,可对于通常所谓脂质体过氧化的过程,给予以合理的解释.     

Solid state nuclear track detectors: Track forming,stabilizing and development processes

Fast moving heavy charged particles passing through solids are mainly losing their energy—in a wide range of velocities—by excitation and ionization processes which result in a more or less stable radiation damage.¹ The radiation damage may consist of broken bonds, free radicals, chemical reaction products, displaced atoms, ionic and electronic defects, dislocation configurations, voids, clusters of defects with and without impurities, nuclei of new phases etc. The nature and stability of this localized radiation damage, termed the “latent” track of the particle depends on the data of the particle and on the physical and chemical properties of the solid. Dielectric materials with low electric and thermal conductivities offer favorable conditions for relatively high local excitation and ionization densities resulting in physical and chemical solid state reactions with relatively stable reaction Products.     

微波液相放电等离子体发射光谱研究

液相放电能够产生各种活性物质,其中羟基自由基(OH),氢自由基(H)被认为是引发液相化学反应的主要活性物种,但由于其活性强寿命短的特点,测量比较困难,由于缺少标准样品,定量测量更为困难。用光学方法测量自由基是一种直接测量方法,其特点是瞬时在线测量,能立即获得数据,进行时间和空间分布测量。为了研究微波水中放电产生的自由基特性,利用发射光谱诊断技术对微波水中放电产生的活性物质进行了在线检测,考察了微波功率、反应器内部压强对OH自由基相对光谱强度的影响,并观测了等离子体中OH自由基强度的空间分布;同时,估算了微波液相等离子体中的电子激发温度。实验结果表明,微波水中放电可以产生大量的OH,H,O自由基,其中OH自由基的相对光谱强度最强,并随微波功率的增加呈现明显上升的趋势,随反应器内部压强的增大而迅速减弱;以OH为主的自由基主要产生于电极尖端附近。微波液相等离子体的电子激发温度约为0.33×104 K。     

Spontaneous formation of free radicals in cryochemical reactions of halogenation of hydrocarbons and nanomaterials

A range of issues related to free-radical processes in polymer-monomer systems is considered. Spectral (EPR, IRS) and other physicochemical methods (calorimetry, chromatography, viscometry) are used to demonstrate that the low-temperature treatment of polymers and monomers with halogens (fluorine, chlorine) is accompanied by the spontaneous formation of free radicals. At F₂ and Cl₂ pressures below 100 Torr, the concentration of radicals reaches 10¹⁷–10¹⁹ spin/g, which can be reproduced in the case of radiolysis only by using doses of several hundred (or thousand) kGy. The formation of radicals through the cleavage of chemical bonds (without external energy impact on the system) is discussed in the framework of the model of low-temperature reactions in polymolecular complexes, involving the simultaneous occurrence of endothermic and exothermic steps in one elementary event with an overall exothermic effect. It is shown that the radicals formed can be used to initiate the polymerization of vinyl and acetylene monomers.     

含萘环聚芳醚酮类聚合物的分子设计与性质研究

聚芳醚酮类聚合物由于具有优良的韧性、刚性、耐热等级高、电性能、耐辐射、耐疲劳、耐冲击、抗蠕变、耐磨、耐热水性好、阻燃性好等特点,在热塑性聚合物领域占有极其重要的位置. 其在航空、航天、核能、信息、通讯、电子电信、石油化工、机械制造、交通运输等高技术领域得到了成功的应用,使许多行业的传统产品实现了更新换代. 但是,随着世界新科技革命的蓬勃发展,对高性能结构材料提出了日益广泛而迫切的需求. 为进一步提高聚芳醚酮类聚合物的性能,满足某些特殊情况下的使用要求（例如高温、高辐照强度）,可考虑对它们进行交联. 使之可用热塑性材料的加工方法加工,然后通过热处理使其交联,成为热固性材料. 这就要求在聚合物链上引入可交联基团. 常用的脂肪族交联基团的引入,会导致聚芳醚酮耐热性降低,而只能寻找芳香族可交联集团的聚合物材料. 本论文的目的是从分子结构设计的角度出发,从合成新型单体入手,采用芳香族亲核取代路线,将萘环引入聚合物主链,合成出一系列的新型含萘环聚芳醚酮类聚合物,并在不同条件下对它们进行了热处理. 主要利用电子自旋共振（ESR）这一手段对热处理前后的聚合物进行了表征,研究了聚合物的热交联行为,讨论了萘环的化学环境、键连位置及热处理条件对交联反应的影响,建议了交联机理.  我们首先通过1,5-萘二酚(1, 5-DHN)、对苯二酚(HQ)和4,4′-二氟二苯酮（DFB）合成了新型高分子量的含1,5-萘二醚型聚醚醚酮无规共聚物（1, 5-PENEK）,发现随着萘环含量的增加, 聚合物的玻璃化转变温度升高,熔点和结晶能力逐步下降直至消失,力学性能略有下降但基本保持了聚芳醚酮的优良性能. 这些性质的改变是由于萘环的引入在增加了聚合物的刚性同时也降低了聚合物的有序排列能力所致. 通过DSC、WAXR检测发现,1,5-萘二醚型聚醚醚酮共聚物（1, 5-PENEK）在320 ℃以上空气中处理时发生交联反应. 随着萘环含量的增加及处理温度的提高,聚合物的玻璃化转变温度增高速度加快,结晶性能迅速下降. 当处理前后的样品用ESR定量检测时,发现只存在一个单峰,并且其幅度随着热处理时间的增加而增强. 增加微波功率时发现在谱峰的两侧有很弱的突起,采用微波功率饱和特性方法证实样品中存在两种性质不同的R₁和R₂自由基. 在不同气氛下处理该样品, 从它们ESR谱的特征推测：R₁可能是RO·自由基,采用改变ESR的检测温度的方法进一步确认热处理后的聚合物中R₁自由基是RO·自由基,并且经计算证明RO·自由基是与分子链中萘环相关联的. 我们又通过模拟的方法证实R₂自由基是萘环自由基. 通过作RO·自由基、萘环自由基的自旋浓度随热处理时间变化曲线发现两种自由基都参与了交联反应,只是RO·自由基的浓度明显高于萘环自由基,在交联反应中起主导作用. 两种自由基浓度随热处理时间的变化趋势相同,即在热处理前期自由基浓度随时间增长很快,中期则变化不大,而后呈线性增长. 可以认为,热处理前期,主要是自由基的激发过程,而中期生成的自由基大多以双基终止的方式被消耗掉,对浓度增长没有明显贡献. 玻璃化转变温度与此相反的变化趋势支持这一结论. 恒温热失重实验表明,1, 5-PENEK在340 ℃热处理时出现明显的分解,说明1, 5-PENEK在340 ℃发生的热交联反应是裂解交联反应. 通过以上测试结果,得到了含1,5-萘二醚型聚醚醚酮共聚物（1, 5-PENEK）在340 ℃热交联的反应机理.  第二部分,我们从1,4-萘二甲酸出发,经过酰氯化反应及付氏酰基化反应,合成了新型单体1,4-二（4-氟苯羰基）萘(1, 4-BFN). 并且利用所得到的单体和4,4′-二氟二苯酮（DFB）与对苯二酚（HQ）通过亲核取代反应合成了含1,4-萘环的聚醚醚酮酮共聚物（1, 4-PEEKNK）. 测试结果表明, 随着萘环含量的增加,1, 4-PEEKNK的玻璃化转变温度升高、 溶解性变好、熔点下降直至消失,1,4-PEEKNK均聚物的力学性能与PEEK相近. 经260 ℃以上热处理的1, 4-PEEKNK均聚物的热分析实验结果表明,随着处理时间或处理温度的增加, 玻璃化转变温度升高. 从而推断在空气中热处理时聚合物发生了交联反应. 结合FT－IR、NMR等提出,交联反应是发生在萘环上的交联反应. 我们同样采用了ESR技术对1, 4-PEEKNK聚合物的交联反应类型进行了研究. 发现自由基的浓度随着处理时间的增加同样经历了3个阶段,由此我们判断1,4-PEEKNK聚合物发生的交联反应为自由基交联反应. 在不同热处理温度下1, 4-PEEKNK聚合物处理8 h的自由基自旋浓度表明在260 ℃和300 ℃热处理时自由基浓度增加的很少,与未处理样品的浓度几乎一致,认为这是由于在此温度下自由基激发的速度相对缓慢, 因此自由基全部被用于交联反应. 但是在340 ℃热处理时,自由基的浓度则急剧增加,这说明在此温度下自由基产生的速度极快甚至也产生了其它种类自由基,虽然聚合物也发生了交联反应,但是有大量自由基剩余而不利于材料的进一步使用. 恒温热失重结果说明在260 ℃热处理的1, 4-PEEKNK未发生裂解反应. 通过以上结果,给出了1, 4-PEEKNK在260 ℃热交联的交联反应机理.  总之,我们合成了两种不同萘环化学环境及不同键连接方式的聚合物,对其基本性质进行了研究,并且发现两种聚合物在空气中于一定温度下热处理时都发生了交联反应,但交联方式及交联机理各有不同. 就综合性质及应用要求而言,我们认为1,4-萘二酮型聚合物PEEKNK作为全芳香性可交联聚芳醚酮类材料应具有很好的应用前景.     

硫化镉胶粒界面自由基反应动力学的ESR研究

用电子自旋共振波谱方法研究了半导体超微粒子表面光诱导电子转移所引发的底物的次级自由基反应动力学过程.结果表明,用含有水溶性草酸盐的硫化镉(CdS)胶体体系产生的COO·^-离子基,可以较方便地引发其它自由基反应,并根据已知的由DMPO捕捉COO·^-的反应速度常数数据,去计算COO·^-基与其它可产生稳定自由基的化合物进行反应的速度常数值,从而在此基础上发展了一种研究自由基反应动力学的行之有效的简便的新途径和新方法,可以较广泛地应用于其它凝聚相的自由基反应动力学体系的研究.     

The electron spin resonance of polycarbonate track detectors

Polycarbonate films are widely used as solid state track detectors (SSTDs) of radiation, but as yet our knowledge of the microscopic nature of the latent track is limited. The processes of chemical etching and thermal annealing are not fully understood. The lack of stability of track parameters bears on the accuracy of the charge determination of energetic heavy nuclei.

We have applied the technique of electron spin resonance, (ESR) in order to seek a correlation between the density of tracks and the growth and decay of free radicals detected by ESR. Samples of polycarbonate were irradiated with thermal neutrons and then etched progressively with NaOH. The ESR signal increased initially and then became weaker as the bulk of the polycarbonate was removed. Other samples were annealed after partial etching. ESR monitoring of this annealing showed that free radicals were recombining, probably due to diffusion processes.     

Spatio-temporal dynamics of cavitation bubble clouds in a low frequency reactor: comparison between theoretical and experimental results.

The propagation of ultrasound through a liquid induces the growth of inceptions and germs into bubbles. In a low frequency reactor, fragmentary transient bubbles emerge due to the acoustic driving. They violently collapse in one cycle and fragment into many smaller bubbles than in turn cavitate. This violent collapse is responsible for the mechanical effects of ultrasounds effects. The latter bubbles gather in a ball-shaped cloud and migrate to pressure antinodes. During their migration, their nonexplosive collapses mainly contribute to activate chemical reactions by producing OH. radicals. Mathematical modelling is performed as a new approach to predict the bubbles field. Through numerical simulation, we determinate emergence sites of mechanically active cavitation bubbles. Calculus are compared with aluminium foil degradation. The modelling of bubble migration allow us to have an insight on the privileged sites of the chemical reactions. Validation of the modelling is made through direct comparison with chemiluminescence photo. All experiments and computations are made in a 28.2 kHz sonoreactor.     

Bubbles in an acoustic field: an overview

Acoustic cavitation is the fundamental process responsible for the initiation of most of the sonochemical reactions in liquids. Acoustic cavitation originates from the interaction between sound waves and bubbles. In an acoustic field, bubbles can undergo growth by rectified diffusion, bubble-bubble coalescence, bubble dissolution or bubble collapse leading to the generation of primary radicals and other secondary chemical reactions. Surface active solutes have been used in association with a number of experimental techniques in order to isolate and understand these activities. A strobe technique has been used for monitoring the growth of a single bubble by rectified diffusion. Multibubble sonoluminescence has been used for monitoring the growth of the bubbles as well as coalescence between bubbles. The extent of bubble coalescence has also been monitored using a newly developed capillary technique. An overview of the various experimental results has been presented in order to highlight the complexities involved in acoustic cavitation processes, which on the other hand arise from a simple, mechanical interaction between sound waves and bubbles.     

紫外光下毛竹的自由基与光电子能谱分析

分析了紫外光照射下毛竹自由基的变化规律和表面化学组成及结构的变化.利用电子自旋共振波谱和X射线光电子能谱技术,分别测量紫外光辐照后毛竹颗粒的自由基波谱和X射线光电子能谱.结果表明:毛竹自由基的光谱分裂因子g=2.003 3,自由基的强度随着辐照时间按Y=1-e-b,Pt规律增加;紫外光照60 min后毛竹表面O/C原子比稍有增加,C-C和C-H含量增加,C-O和C=O含量减少,-O-C=O含量增加为原来的3倍左右,说明毛竹表面生成了一些含氧官能团或碳的氧化态增高.     

Computational study of state equation effect on single acoustic cavitation bubble’s phenomenon

Many models have been established to study the evolution of the bubble dynamics and chemical kinetics within a single acoustic cavitation bubble during its oscillation. The content of the bubble is a gas medium that generates the evolution of a chemical mechanism governed by the internal bubble conditions. These gases are described by a state equation, linking the pressure to the volume, temperature and species amounts, and influencing simultaneously the dynamical, the thermal and the mass variation in the cavitation bubble. The choice of the state equation to apply has then a non-neglected effect on the obtained results. In this paper, a comparative study was conducted through two numerical models based on the same assumptions and the same scheme of chemical reactions, except that the first one uses the ideal gas equation to describe the state of the species, while the second one uses the Van der Waals equation. It was found that though the dynamic of the bubble is not widely affected, the pressure and temperature range are significantly increased when passing from an ideal gas model to a real one. The amounts of chemical products are consequently raised to approximately the double. This observation was more significant for temperature and pressure at low frequency and high acoustic amplitude, while it is noticed that passing from ideal gas based approach to the Van der Waals one increases the free radicals amount mainly under high frequencies. When taking the results of the second model as reference, the relative difference between both results reaches about 60% for maximum attained temperature and 100% for both pressure and free radicals production.     

等离子体中活性粒子分析及化学动力学机理

利用发射光谱测量技术分析了介质阻挡放电等离子体激励空气产生的主要活性粒子,利用零维等离子体动力学模型模拟了甲烷/空气中放电阶段主要活性粒子的演化规律,并通过敏感性与化学路径分析研究了O原子影响甲烷点火过程的化学动力学机理。研究表明：空气中介质阻挡放电等离子体主要产生N2和O2的激发态粒子,激发态粒子的数密度随着电压的增加而增大;激发态粒子经过一系列物理化学反应最终转化成若干自由基,其中O原子的摩尔分数最大;O原子缩短甲烷点火延迟时间一个量级,原因在于添加O原子后甲基（CH3）的氧化途径由自点火过程中的经O2直接氧化为CH3O和CH2O转变为经HO2和O原子氧化为CH3O和CH2O,由于后者的基元反应速率快,因而明显缩短了点火延迟时间。     

等离子体中活性粒子分析及化学动力学机理

利用发射光谱测量技术分析了介质阻挡放电等离子体激励空气产生的主要活性粒子,利用零维等离子体动力学模型模拟了甲烷/空气中放电阶段主要活性粒子的演化规律,并通过敏感性与化学路径分析研究了O原子影响甲烷点火过程的化学动力学机理。研究表明:空气中介质阻挡放电等离子体主要产生N2和O2的激发态粒子,激发态粒子的数密度随着电压的增加而增大;激发态粒子经过一系列物理化学反应最终转化成若干自由基,其中O原子的摩尔分数最大;O原子缩短甲烷点火延迟时间一个量级,原因在于添加O原子后甲基(CH3)的氧化途径由自点火过程中的经O2直接氧化为CH3O和CH2O转变为经HO2和O原子氧化为CH3O和CH2O,由于后者的基元反应速率快,因而明显缩短了点火延迟时间。     

EPR spectroscopic characterization of biological thiyl radicals as PBN spin-trap adducts

While the importance of thiols and their derivatives in biological processes is widely appreciated, the elucidation of the roles played by thiyl radicals in these processes — being hampered by the radical reactivity that makes their detection and characterization difficult — is lagging. The results of a spin-trap EPR study are reported which advance the capability for detecting and identifying thiyl radicals. Adducts with PBN (α-phenyl-N-_t-butylnitrone) of thiyl radicals derived from the biologically abundant low-molecular-weight thiols cysteine, homocysteine, and glutathione are examined. Significant differences in the β-proton hyperfine couplings of the various adducts are observed; both the EPR lineshapes and the radical adduct lifetimes show trends reflective of the molecular size of the trapped thiyl radical. These results indicate that EPR spectroscopy can be useful in identifying specific thiyl radicals that may be involved in the biochemical reactions of low-molecular-weight thiols, protein thiols, and their derivatives.     

H-ZSM-5沸石表面吸附态烯烃正离子自由基的不等价磁相互作用的ESR研究

本文报道在经氧气高温处理后的H-ZSM-5沸石所生成的多种开链及闭环的乙烯正离子基衍生物、利用计算机模拟了解在沸石孔洞内的化学吸附情形、同时帮助判定正确的超精细作用产生的非等价质子偶合常数,利用-乙烯正离子基的磁不对称性了解自由基与沸石产生的作用及离子-分子间的化学反应.本文提出一个新方程式,它利用分子的对称性来了解这些正离子自由基的非平面性的几何形状.