O/W型微乳液中萘醌光解自由基的化学诱导动态电子自旋极化研究(英文)

利用高时间分辨的电子自旋共振波谱仪 (TRESR) ,研究了光解萘醌自由基在不同表面活性剂微乳液形成的“笼效应”下的化学诱导动态电子自旋极化 (CIDEP) ,得到了阴离子自由基的信号 ,并与胶束体系中的CIDEP进行了比较 ,发现两者有一定的差别 ,主要是萘醌在微乳液中增溶位置的不同导致了光解反应机理的不同     

Adjusting Some Properties of Poly(methacrylic acid) (Nano)Composite Hydrogels by Means of Silicon-Containing Inorganic Fillers

The present work aims to show how the main properties of poly(methacrylic acid) (PMAA) hydrogels can be engineered by means of several silicon-based fillers (Laponite XLS/XLG, montmorillonite (Mt), pyrogenic silica (PS)) employed at 10 wt% concentration based on MAA. Various techniques (FT-IR, XRD, TGA, SEM, TEM, DLS, rheological measurements, UV-VIS) were used to comparatively study the effect of these fillers, in correlation with their characteristics, upon the structure and swelling, viscoelastic, and water decontamination properties of (nano)composite hydrogels. The experiments demonstrated that the nanocomposite hydrogel morphology was dictated by the way the filler particles dispersed in water. The equilibrium swelling degree (SDe) depended on both the pH of the environment and the filler nature. At pH 1.2, a slight crosslinking effect of the fillers was evidenced, increasing in the order Mt < Laponite < PS. At pH > pKa_MAA (pH 5.4; 7.4; 9.5), the Laponite/Mt-containing hydrogels displayed a higher SDe as compared to the neat one, while at pH 7.4/9.5 the PS-filled hydrogels surprisingly displayed the highest SDe. Rheological measurements on as-prepared hydrogels showed that the filler addition improved the mechanical properties. After equilibrium swelling at pH 5.4, G’ and G” depended on the filler, the Laponite-reinforced hydrogels proving to be the strongest. The (nano)composite hydrogels synthesized displayed filler-dependent absorption properties of two cationic dyes used as model water pollutants, Laponite XLS-reinforced hydrogel demonstrating both the highest absorption rate and absorption capacity. Besides wastewater purification, the (nano)composite hydrogels described here may also find applications in the pharmaceutical field as devices for the controlled release of drugs.     

Repair of Protein Radicals by Antioxidants

In vivo, proteins are the main targets for radicals and other reactive species. Their reactions result in formation of amino acid radicals on the protein surface that often yield tryptophan and tyrosyl radicals or, in the presence of O₂, protein peroxyl radicals and hydroperoxides. All these species may propagate damage to biomolecules. Low molecular weight antioxidants, such as ascorbate, urate, and glutathione, are part of the defense system and function by repairing damaged proteins. We briefly review the existing knowledge about protein and amino acid radicals and their repair by antioxidants, including results of our investigations. The main question addressed is whether the antioxidants ascorbate, urate, and glutathione are able to repair amino acid radicals in model compounds and in proteins in vitro by pulse radiolysis. We show that ascorbate and urate repair tryptophan and tyrosyl radicals efficiently and inhibit proton-coupled electron transfer from tyrosine residues to tryptophan radicals in a number of proteins. In contrast, repair by glutathione is much slower. Ascorbate also rapidly reduces the peroxyl radicals of the N-acetylamide derivatives of glycine, alanine, and proline, whereas glutathione reduces peroxyl radicals in lysozyme. In vivo urate, ascorbate, and glutathione may prevent biological damage or, at least, reduce its rate, because they: (a) repair tryptophan and tyrosyl radicals in proteins and (b) reduce protein peroxyl radicals to the corresponding protein hydroperoxides. Most likely, in vivo, ascorbate and glutathione do not inhibit the reaction of C-centered amino acid radicals with O₂. Glutathione is less efficient that urate and ascorbate in repairing protein radicals; furthermore, the resulting glutathiyl radical is harmful. Ascorbate may be the more important repair agent in cells and tissues characterized by high ascorbate concentrations, such as the lens and brain; urate may be mainly responsible for repair in tissue compartments with higher urate concentrations, such as in plasma and saliva.     

单体3,5-二(2-炔基丙氧基)与3,5-二(4-叠氮丁氧基)苯甲酸甲酯苯甲酸甲酯的合成与表征

目的:单体分子3,5-二(2-炔基丙氧基)苯甲酸甲酯与3,5-二(4-叠氮丁氧基)苯甲酸甲酯的合成与表征。方法:采用"Williamson"醚化反应和与叠氮化钠的亲核取代反应,合成单体分子3,5-二(2-炔基丙氧基)苯甲酸甲酯与3,5-二(4-叠氮丁氧基)苯甲酸甲酯。用核磁共振波谱(1H NMR)及红外光谱(FTIR)对合成单体结构进行表征。     

单体3,5-二(2-炔基丙氧基)苯甲酸甲酯的合成与表征

目的:单体分子3,5-二(2-炔基丙氧基)苯甲酸甲酯的合成与表征。方法:采用3,5-二羟基苯甲酸甲酯与卤代烷进行Williamson醚化反应和与叠氮化钠的亲核取代反应,合成单体分子3,5-二(2-炔基丙氧基)苯甲酸甲酯。通过1H NMR和FTIR对合成单体进行结构表征。     

聚三唑的后修饰

目的:对合成的聚三唑进行后修饰。方法:先用水合肼还原聚三唑重复单元上的酯基,将酰肼基团引入到聚合物结构中。在碱性条件下酰肼基团与二硫化碳反应。然后再与水合肼发生反应环合。酸化后得到侧基为氨基和巯基取代的1,2,4-三氮唑环修饰的聚三唑。     

微纳米气泡形成羟基自由基的研究进展

从微纳米气泡溶液中是否可以产生·OH、·OH的鉴别方法、·OH的生成机理以及强化·OH的生成等几个方面论述了微纳米气泡溶液中生成·OH的研究进展.电子自旋共振技术和荧光分光光度法作为检测·OH的2种技术,均存在一定的误导性,对于荧光分光光度法,最重要的就是排除H2 O2的干扰.此外,目前要获得含有高浓度·OH的微纳米气...     

Fe(phen)_3~(2 )光度法研究Fenton试剂体系中·OH生成率的影响因素

提高Fenton试剂在废水处理工艺中的效率 ,关键在于提高体系中·OH的生成率与利用率。本文采用间接测定·OH的方法 ,对Fenton试剂体系中·OH的表观生成率进行测定。并详细考查了催化剂Fe2 的浓度、H2 O2 的投加量、pH值、反应时间及反应温度等因素对体系中·OH的表观生成率的影响。为提高Fenton试剂处理废水的效率提供了有用的参数     

Kinetics of Reduction of Some CoIII(NH3)5 L Complexes by Substituted Pyridinyl Radicals. A Pulse Radiolytic Study

The rates of reduction of some Co^III pentaamine complexes by HINA·, and , HNA·, radicals were measured. It was found that HNA· is more reactive than HINA·. The redox potential for the couple HINA·/HINA⁺ was calculated, E° = 0.80 ± 0.02 V. In the presence of large excess of NA, a catalytic enhancement in the reduction of Co^III(NH₃)₅ NA and Co^III(NH₃)₅ Pyridine by Eu²⁺ was observed. The difference in the mechanism of reduction of Co^III(NH₃)₅ X by Eu²⁺ where X = NA or INA is discussed. The redox potential of the HNA·/HNA⁺ couple was estimated, 0.80 < E° < 1.1 V.     

Radicals generated in autoxidized methyl linoleate by light irradiation

The structure of free radicals generated in the autoxidation of methyl linoleate (ML) was studied by the spin trapping technique using deuterated nitrosodurene, (CD₃)₄C₆HNO, as the spin trap. The secondary alkyl radicals were trapped after irradiation of ML with UV light. The formation rate of secondary alkyl radicals increased upon shortening the wavelength of irradiation light and was closely correlated with the peroxide value of autoxidized ML when a UV light longer than 250 nm was employed. When hydroperoxides separated from autoxidized ML were added to ML, the relationship between the formation rate of secondary alkyl radicals and the amounts of added hydroperoxides was nearly linear. These results suggest that secondary alkyl radicals are generated by proton abstraction of the active radicals, such as RO and HO, which are produced by the photolysis of hydroperoxides with UV light. The spin trapping technique can be applied to the study of lipid oxidation and/or photolysis of autoxidized lipid.     

Initiation and Prevention of Biological Damage by Radiation-Generated Protein Radicals

Ionizing radiations cause chemical damage to proteins. In aerobic aqueous solutions, the damage is commonly mediated by the hydroxyl free radicals generated from water, resulting in formation of protein radicals. Protein damage is especially significant in biological systems, because proteins are the most abundant targets of the radiation-generated radicals, the hydroxyl radical-protein reaction is fast, and the damage usually results in loss of their biological function. Under physiological conditions, proteins are initially oxidized to carbon-centered radicals, which can propagate the damage to other molecules. The most effective endogenous antioxidants, ascorbate, GSH, and urate, are unable to prevent all of the damage under the common condition of oxidative stress. In a promising development, recent work demonstrates the potential of polyphenols, their metabolites, and other aromatic compounds to repair protein radicals by the fast formation of less damaging radical adducts, thus potentially preventing the formation of a cascade of new reactive species.     

高温下含硅气相介质与多壁碳纳米管的作用机理

采用单质硅粉、铝粉和二氧化硅微粉（Al＋SiO2）,以及硅粉和二氧化硅微粉（Si＋SiO2）作为3种不同硅源,在埋碳床中于1 000～1 500℃处理多壁碳纳米管（multi-walled carbon nanotubes,MWCNTs）,研究了不同含硅气相介质与MWCNTs的作用机理。结果表明：不同温度条件下以Si为...     

Fe(phen)2+3光度法研究Fenton试剂体系中·OH生成率的影响因素

提高Fenton试剂在废水处理工艺中的关键在于提高体系中·OH的生成率与利用率.本文采用间接测定·OH的方法,对Fenton试剂体系中·OH的表观生成率进行测定.并详细考查了催化剂Fe2+的浓度、H2O2的投加量、pH值、反应时间及反应温度等因素对体系中·OH的表观生成率的影响.为提高Fenton试剂处理废水的效率提供了有用的参数.     

Free Radicals and ROS Induce Protein Denaturation by UV Photostability Assay

Oxidative stress, photo-oxidation, and photosensitizers are activated by UV irradiation and are affecting the photo-stability of proteins. Understanding the mechanisms that govern protein photo-stability is essential for its control enabling enhancement or reduction. Currently, two major mechanisms for protein denaturation induced by UV irradiation are available: one generated by the local heating of water molecules bound to the proteins and the other by the formation of reactive free radicals. To discriminate which is the likely or dominant mechanism we have studied the effects of thermal and UV denaturation of aqueous protein solutions with and without DHR-123 as fluorogenic probe using circular dichroism (CD), synchrotron radiation circular dichroism (SRCD), and fluorescence spectroscopies. The results indicated that the mechanism of protein denaturation induced by VUV and far-UV irradiation were mediated by the formation of reactive free radicals (FR) and reactive oxygen species (ROS). The development at Diamond B23 beamline for SRCD of a novel protein UV photo-stability assay based on consecutive repeated CD measurements in the far-UV (180–250 nm) region has been successfully used to assess and characterize the photo-stability of protein formulations and ligand binding interactions, in particular for ligand molecules devoid of significant UV absorption.     

Aldehydes from Oxidized Lipids Can React with 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) Free Radicals in Isooctane Systems

Oxidized lipids can decrease the absorbance of 2,2-diphenyl-1-picrylhydrazyl (DPPH) in isooctane. However, the compounds responsible for the decrease in DPPH absorbance are still not known. Major factors and possible compounds decreasing the DPPH absorbance during lipid oxidation were identified using linoleic and oleic acid model systems. Changes in the hydroperoxides and conjugated dienoic acid value in thermally oxidized linoleic acid were not highly correlated with those of DPPH absorbance under air-tight and nitrogen flushing conditions. Radical scavenging compounds from oxidized oleic acid were tentatively identified as mixtures of aldehydes, alcohols, and acids. Aldehydes from oxidized fatty acids including pentanal, t-2-heptenal and t-2-nonenal can react with DPPH, whereas most alcohols and hydrocarbons did not show DPPH scavenging activity. Aldehydes rather than conjugated dienes and hydroperoxides may be the radical scavenging compounds from oxidized lipids. The results of this study will help to understand better the changes in oxidation products during lipid oxidation.     

Formation of Hydrazyl Radicals and Hydrazo Compounds by Photoreduction of Azo Dyes

The photoreduction of eighteen different monoazo dyes in aqueous and ethanolic solutions, containing d, l -mandelic acid or acetone as hydrogen donors, to the corresponding amines has been investigated by flash-photolysis and rapid-flow techniques. The photoreduction of azo dyes proceeds in stages involving hydrazyl radicals and hydrazo compounds. The former are formed in a rapid reaction of the azo dyes with the active reducing agent produced upon absorption of light by the hydrogen donor. These radicals are unstable and disproportionate with formation of hydrazo compounds and regeneration of the original azo dye. The hydrazo compounds are also unstable and decompose with formation of amines and regeneration of the dye. The reaction schemes presented are supported by kinetic evidence and electron spin resonance measurements.     

Electron-Induced Repair of 2′-Deoxyribose Sugar Radicals in DNA: A Density Functional Theory (DFT) Study

In this work, we used ωB97XD density functional and 6-31++G** basis set to study the structure, electron affinity, populations via Boltzmann distribution, and one-electron reduction potentials (E°) of 2′-deoxyribose sugar radicals in aqueous phase by considering 2′-deoxyguanosine and 2′-deoxythymidine as a model of DNA. The calculation predicted the relative stability of sugar radicals in the order C4′^• > C1′^• > C5′^• > C3′^• > C2′^•. The Boltzmann distribution populations based on the relative stability of the sugar radicals were not those found for ionizing radiation or OH-radical attack and are good evidence the kinetic mechanisms of the processes drive the products formed. The adiabatic electron affinities of these sugar radicals were in the range 2.6–3.3 eV which is higher than the canonical DNA bases. The sugar radicals reduction potentials (E°) without protonation (−1.8 to −1.2 V) were also significantly higher than the bases. Thus the sugar radicals will be far more readily reduced by solvated electrons than the DNA bases. In the aqueous phase, these one-electron reduced sugar radicals (anions) are protonated from solvent and thus are efficiently repaired via the “electron-induced proton transfer mechanism”. The calculation shows that, in comparison to efficient repair of sugar radicals by the electron-induced proton transfer mechanism, the repair of the cyclopurine lesion, 5′,8-cyclo-2′-dG, would involve a substantial barrier.