钛基亚氧化钛电极电化学降解性能研究

采用SEM、EDS对钛基亚氧化钛电极进行形貌和成分表征,用线性极化曲线法和循环伏安法测试电化学性能,通过降解模拟污水测试降解性能以及用荧光光谱法检测自由基。结果表明,钛基亚氧化钛电极上不能发生直接氧化反应,但是电极析氧电位可达2.18 V(vs.SCE),并且检测到生成大量·OH,是一种类似于Ti/SnO_2的惰性电极,在Na Cl和Na2SO4电解质溶液中电流效率分别达40.95%和22.52%,降解效果优于Ti/SnO_2和Ti/Ru Ir电极。     

微波等离子体化学气相沉积金刚石光谱分析

采用等离子体光谱分析微波等离子体化学气相(MPCVD)沉积金刚石过程中基团的空间分布及甲烷浓度变化时基团浓度的变化情况.实验过程中分别测量了氢原子的Hα(656.19 nm)、Hβ(486.71 nm)和Hγ(434.56 nm)谱线,以及基团CH(431.31 nm)、C2(515.63 nm)谱线.结果表明:氢原子和基团CH、C2的浓度沿等离子体柱的径向先增加再减小.随着甲烷浓度逐步增加,氢原子及基团CH、C2的浓度相应增加,其中C2基团所受影响最大.     

Iron enhances generation of fibrin fibers in human blood: Implications for pathogenesis of stroke

Stroke is associated with the intracerebral formation of fibrin clots which may lead to irreversible brain damage. Thrombolytic therapies employ a variety of natural and/or recombinant plasminogen activators to initiate fibrinolytic degradation of cerebral thrombi. However, such therapies when installed beyond 4‐ to 6‐h window, may fail to achieve the expected outcome. This is due to the hydroxyl radical‐induced modification of fibrin(ogen) molecules rendering them refractory to fibrinolytic degradation, but no cause of the increased free radical generation in stroke was offered. Here, we show by means of electron microscopy that iron ions added to human blood dramatically enhances fibrin fibers formation with thrombin, and significantly delays fibrinolysis during spontaneous clotting of native blood. Iron ions caused the appearance dense matted fibrin deposits, similar, if not identical, to those observed in plasma of patients with stroke. These results may explain a known relationship between thrombotic diseases and the increased body concentrations of free iron and/or hemoglobin derivatives. We conclude that any action resulting in the inhibition of hemostatic abnormalities, as well as in the reduction of body free iron and scavenging of hydroxyl radicals (e.g., by polyphenols) can potentially prevent pathological reactions associated with consequences of stroke. Microsc. Res. Tech. 75:1185–1190, 2012. © 2012 Wiley Periodicals, Inc.     

Study of elementary reactions of free radicals formed on oxide and platinum containing catalysts

The formation of alkylperoxy radicals on catalysts CuCr₂O₄/ -Al₂O₃, Pt /--Al₂O₃ and on alumina upon the interaction of amines and alcohols with oxygen has been observed applying the matrix isolation ESR technique. Surface-generated gas phase radicals are shown to initiate a radical chain reaction. The efficiency of the yield of radicals depends on the catalyst mass and its arrangement in a reactor: the desorption of radicals into the gas phase occurs primarily from the outer geometrical surface of catalyst granules.     

超声激活血卟啉抗肿瘤疗法的研究现状

首先介绍了超声作用的物理机理和血卟啉及其衍生物的化学结构及物理化学性质,对超声激活血卟啉抗肿瘤疗法(声动力学疗法)近15年国内外的试验进展情况进行了总结,对比了不同参数超声系统对不同细胞系肿瘤的作用效果。重点探讨了超声激活血卟啉抑制肿瘤增殖的物理、化学和生物学机理,着重介绍了单线态氧机制和自由基理论,并对今后的基础研究和临床实践进行了展望。     

类胡萝卜素抗氧化性质的研究

类胡萝卜素有多种生物学作用，包括抑癌防衰、减低一些疾病发生。其重要原因之一是它们的生物抗氧化剂特性：猝灭^1O2、清除自由基、抑制脂类过氧化与细胞呼吸爆发的抗氧化作用。采用H2O2－NaOCl体系产生的^1O2的发光法研究^1O2的猝灭作用，脉冲辐解法研究与CCl3OO的反应，测定自由基引发的亚油酸氢过氧化物生成和脂质体过氧化产物硫代巴比妥酸反应物生成研究抑制脂质过氧化，通过依赖于鲁米诺的化学发光法与无细胞模拟体系研究对巨噬细胞呼吸爆发的影响。研究表明：类胡萝卜素通过物理过程猝灭^1O2，与CCl3OO发生反应生成加合物与自由基正离子，可抑制自由基引发的脂质过氧化，可清除巨噬细胞呼吸爆发所释放的活性氧自由基，降低细胞依赖于鲁米诺的化学发光，保护宿主细胞与组织，增强细胞免疫反应活性。     

Radiation- and Photo-Induced Oxidation Pathways of Methionine in Model Peptide Backbone under Anoxic Conditions

Within the reactive oxygen species (ROS) generated by cellular metabolisms, hydroxyl radicals (HO^•) play an important role, being the most aggressive towards biomolecules. The reactions of HO^• with methionine residues (Met) in peptides and proteins have been intensively studied, but some fundamental aspects remain unsolved. In the present study we examined the biomimetic model made of Ac-Met-OMe, as the simplest model peptide backbone, and of HO^• generated by ionizing radiation in aqueous solutions under anoxic conditions. We performed the identification and quantification of transient species by pulse radiolysis and of final products by LC-MS and high-resolution MS/MS after γ-radiolysis. By parallel photochemical experiments, using 3-carboxybenzophenone (CB) triplet with the model peptide, we compared the outcomes in terms of short-lived intermediates and stable product identification. The result is a detailed mechanistic scheme of Met oxidation by HO^•, and by CB triplets allowed for assigning transient species to the pathways of products formation.     

The role of an interfacial interpenetrating polymer network formation on the adhesion of resin composite layers in immediate dentin sealing

The aim of this study was to evaluate the influence of chemical and physical processes at the resin-composite and composite-cement interface as a function of the resin composite's water exposure on the bond strength (BS) between these two components. The free-radical concentration was studied using electron paramagnetic resonance (EPR), while the chemical changes at the resin composite's surface were studied using attenuated total-reflection FTIR spectroscopy (ATR-FTIR). The free-radical concentration in the studied samples dropped to 10% in 24 h, indicating that prolonged BS values do not correlate with the free-radical concentration. An alternative bonding mechanism between the resin composite and the composite cement was proposed, based on the formation of an interpenetrating polymer network (IPN) layer at the interface. As proven using ATR-FTIR spectroscopy, changes occurred at the resin composite's surface as a consequence of water exposure, comprising the diffusion of water molecules into the resin composite. These changes reduced the diffusion rate of the composite cement's phosphorus-containing monomers into the resin composite, as shown by the linescan SEM-EDS analysis of phosphorus, thus reducing the thickness of the IPN layer at the interface and consequently reducing the BS between both components.This study reveals that the concentration of free radicals at the surface of the resin composite is only relevant immediately after the polymerisation to the bond strength between the resin composite and the composite cement. Therefore, an alternative explanation is given by applying the theory of the formation of a gradient IPN at the interface between the resin composite and the adhesive cement by changes in the rate of diffusion of the adhesive cement's monomers into the resin composite as a function of the resin composite's exposure to water.