球形纳米银颗粒与人血清白蛋白相互作用的研究

通过化学还原法合成了球形银纳米颗粒(Ag NPs),用电镜对其形貌进行了表征;利用紫外可见吸收光谱法、荧光光谱法以及扫描电镜研究了其与人血清白蛋白(HSA)的结合作用。随着其浓度的增加,混合溶液的紫外吸收峰强度增加,但荧光强度则发生了明显的猝灭。光谱学实验结果表明,Ag NPs与HSA在溶液中发生了相互作用,此结果也通过扫描电镜实验得到了验证。由荧光实验还可获得Ag NPs与HSA相互作用的结合常数、结合位点数以及吉布斯自由能变,由这些热力学数据可知Ag NPs与HSA可以自发结合,并成缔合物。     

金纳米花的合成及其与人血清白蛋白相互作用的研究

采用晶种法合成了金纳米花（AuNFs）。利用紫外可见吸收光谱法和原子力显微镜方法对金纳米花进行了表征,结果表明制备的金纳米花呈蓝紫色,在549nm处有特征吸收峰,且形状为花状。借助紫外可见吸收光谱法和荧光光谱法研究了AuNFs与人血清白蛋白（HSA）的结合过程。当AuNFs与HSA相互作用时,随着AuNFs溶液浓度的增加,HSA的紫外吸收峰强度也随之增加,但荧光光谱强度则发生了猝灭。由变温荧光实验可以获得两者相互作用的热力学参数,如结合常数（K_a）、吉布斯自由能变（ΔG）、熵变（ΔS）、焓变（ΔH）。ΔG<0表明在溶液中AuNFs与HSA可以自发结合发生反应并形成复合物;ΔH<0、ΔS<0表明结合过程以范德华力和氢键为主。同步荧光和3D荧光实验均表明,AuNFs的存在使得HSA的构象以及周围的环境发生了改变。     

水溶性羟基化单壁碳纳米管与人血清白蛋白之间的相互作用研究

利用荧光光谱、UV吸收光谱、同步荧光光谱和透射电子显微镜等技术较为系统地研究了水溶性羟基化单壁碳纳米管与人血清白蛋白(HSA)的相互作用. 实验发现, 这种羟基化单壁碳纳米管可以明显猝灭HSA的内源荧光, 且猝灭效应随碳纳米管浓度增大而增强. 同时, HSA对水溶性羟基化单壁碳纳米管起到一定的分散和稳定作用. 同步荧光光谱表明, 二者之间的相互作用可导致HSA的构象发生变化, HSA的色氨酸残基荧光信号发生2 nm的红移, 表明色氨酸残基周围微环境的极性降低.     

银纳米线与BSA相互作用的光谱学研究

主要研究了粒径为60 nm的银纳米线与牛血清白蛋白(BSA)之间的相互作用.利用紫外可见吸收光谱法和荧光光谱法对反应体系进行了光谱学实验研究.实验结果表明,随着银纳米线溶液浓度的增加,反应体系的紫外吸收峰强度增大.但是,荧光强度却明显猝灭.由荧光结果可以得知银纳米线和BSA的相互作用过程是静态猝灭;同步荧光光谱结果表明,银纳米线对蛋白质周围的环境产生了影响.由变温荧光实验结果还可获得银纳米线与BSA相互作用的结合常数、结合位点数以及吉布斯自由能变.由热力学数据可知银纳米与牛血清白蛋白可以自发结合发生反应,且主要结合力为范德华力和氢键.     

白藜芦醇类似物与人血清白蛋白的相互作用

采用荧光光谱、三维荧光光谱、紫外吸收光谱研究白藜芦醇类似物(Z)-2-(3,4-二甲氧苯基)-3-(4-二甲氨基苯基)丙烯腈(HCQ)与人血清白蛋白(HSA)的相互作用,探讨其作为抗肿瘤药物的可能。结果发现HCQ与HSA形成了基态配合物,HCQ主要结合于HSA的位点Ⅰ,与位点Ⅱ也有微量的结合,反应为自发的放热反应,其ΔH、ΔS、ΔG均小于零,二者之间的结合力为氢键或者范德华力,结合常数为104～105数量级。HCQ与HSA的结合使HSA构象发生变化,Trp-214所处的环境疏水性增加,使得其内源性荧光显著降低。说明合成的白藜芦醇类似物能够与人血清白蛋白结合。     

光谱及电化学方法研究头孢哌酮钠和盐酸环丙沙星与人血清白蛋白的拮抗作用

在模拟生理条件下,用荧光光谱、紫外吸收光谱并结合电化学方法,研究了头孢哌酮钠(CPZ)和盐酸环丙沙星(CPFX)单独存在与同时存在时与人血清白蛋白(HSA)的相互作用。结果表明:药物与HSA的作用力主要为静电力,HSA的荧光猝灭为静态猝灭;药物与HSA结合位点数约为1;CPZ与CPFX间存在拮抗作用;拮抗作用使药物与HSA间的结合距离r值降低。电化学方法研究表明药物与蛋白相互作用形成了非电活性的的超分子化合物,使得溶液中游离的药物浓度降低。     

光谱法及分子对接研究邻苯二甲酸单乙基己基酯与人血清白蛋白的相互作用

通过荧光光谱法、紫外分光光度法以及分子对接技术探究邻苯二甲酸单乙基己基酯(MEHP)与人血清白蛋白(HSA)之间的相互作用及其作用机制。光谱学数据显示,MEHP诱导HSA内源荧光猝灭是因为两者间发生非辐射能量转移并形成稳定的复合物;不同温度下的热力学常数表明范德华力或氢键为MEHP与HSA结合的主要驱动力;三维荧光光谱结果证实MEHP改变了HSA的构象;同步荧光光谱和位点实验表明,MEHP在位点Ⅰ与HSA结合。根据光谱学的研究结果,采用分子对接技术模拟MEHP与HSA在分子水平上的相互作用机制,结果与光谱学研究结果一致。     

光谱技术结合分子模拟测定塑化剂邻苯二甲酸二正辛酯与人血清白蛋白相互作用模式

在生理酸度(pH 7.4)条件下,采用荧光光谱、紫外-可见吸收光谱、圆二色谱(CD)和红外光谱(FT-IR)等多种光谱方法并结合分子模拟技术,测定了塑化剂邻苯二甲酸二正辛酯(DnOP)与人血清白蛋白(HSA)的相互作用模式。荧光滴定结果表明,DnOP对HSA内源荧光的猝灭机制为形成HSA-DnOP复合物的静态猝灭,其在不同温度下的熵变(ΔS°)和焓变(ΔH°)分别为35.32 J·mol-1·K-1和-9.13 kJ·mol-1,表明结合反应主要由疏水作用和氢键驱动。位点竞争实验表明DnOP与曙红Y发生了置换反应,揭示DnOP主要结合在HSA亚结构域ⅡA(SiteⅠ位),分子模拟结果显示,DnOP插入亚结构域ⅡA的疏水空腔,通过疏水作用以及DnOP的羰基氧与His242氨基酸残基间形成的氢键与蛋白结合,实验结果与荧光光谱及位点竞争实验一致。紫外-可见光谱、CD及FT-IR光谱的分析结果表明,DnOP与HSA结合导致了HSA二级结构发生变化,降低了HSA中α-螺旋的含量,并诱导HSA的多肽链发生部分伸展。     

一种缩氨基硫脲类衍生物探针测定生物样品中的蛋白质含量

在Tris-HCl缓冲溶液体系中(pH=7.4),研究了1,4-二羟基-2-甲酰基-9,10-蒽醌缩对甲氧基苯基氨基硫脲(EN)与人血清白蛋白(HSA)体系的荧光猝灭光谱和三维荧光光谱,证明EN与HSA可以发生相互作用,使人血清白蛋白的疏水微环境的极性以及构象发生变化。 考察了Δλ值、反应介质和离子强度等因素对体系同步荧光光谱特征及强度的影响。 在此基础上,建立了以EN为分子探针,运用固定波长同步荧光光谱法测定生物样品中的蛋白质含量的方法。 在最佳实验条件下,体系同步荧光强度与HSA在1.380~165.6 mg/L范围内呈良好的线性关系。 对11份空白溶液进行平行测定,检出限达到0.414 mg/L,相对标准偏差为1.52%。 运用此方法对血清、唾液、尿液进行了加标回收实验,回收率在98.4%～105%。 且同步荧光光谱法测定结果与考马斯亮蓝法基本一致。     

荧光与紫外光谱法研究柚皮素与人血清白蛋白的结合模式

在模拟生理条件下,利用荧光光谱法和紫外吸收光谱法研究了柚皮素(NG)与人血清白蛋白(HSA)的相互作用。实验结果表明,NG对HSA的内源性荧光具有猝灭作用,属于静态猝灭过程。计算了NG-HSA体系的结合常数、结合位点数及反应的热力学参数ΔG,ΔH和ΔS,由此推出二者主要通过氢键和范德华力自发形成了摩尔比为1∶1的非共价复合物。依据Frster非辐射能量转移理论求得二者之间的结合距离为3.41 nm。三维荧光、同步荧光光谱和结合位点取代实验指出,NG主要与HSA的III A亚结构域中site II位点的酪氨酸结合。     

Characterization of nanomaterials in food by electron microscopy

Engineered nanomaterials (ENMs) are increasingly being used in the food industry. In order to assess the efficacy and the risks of these materials, it is essential to have access to methods that not only detect the nanomaterials, but also provide information on the characteristics of the materials (e.g., size and shape).This review presents an overview of electron microscopy (EM)-based methods that have been, or have the potential to be, applied to imaging ENMs in foodstuffs. We provide an overview of approaches to sample preparation, including drying, chemical treatment, fixation and cryogenic methods. We then describe standard and non-standard EM-based approaches that are available for imaging prepared samples. Finally, we present a strategy for selecting the most appropriate method for a particular foodstuff.     

Direct Imaging of Octahedral Distortion in a Complex Molybdenum Vanadium Mixed Oxide

Complex Mo,V‐based mixed oxides that crystallize in the orthorhombic M1‐type structure are promising candidates for the selective oxidation of small alkanes. The oxygen sublattice of such a complex oxide has been studied by annular bright field scanning transmission electron microscopy. The recorded micrographs directly display the local distortion in the metal oxygen octahedra. From the degree of distortion we are able to draw conclusions on the distribution of oxidation states in the cation columns at different sites. The results are supported by X‐ray diffraction and electron paramagnetic resonance measurements that provide integral details about the crystal structure and spin coupling, respectively.     

Analytical electron microscopy of materials

Analytical electron microscopy enables combined crystallographic and chemical information with a high spatial resolution to be gained from microregions of electron-transparent specimens. This is reached by the combined application of imaging, diffraction and spectroscopic methods, using either a dedicated scanning transmission electron microscope or a conventional high-resolution electron microscope (having a strong objective lens) equipped with suitable X-ray or electron spectrometers. Of the diffraction methods especially the technique of convergent beam diffraction is used, yielding valuable information on crystal structures, lattice parameter changes, symmetry variations and crystal perfection, respectively. For chemical analysis, either energy-dispersive X-ray spectroscopy (EDX) is used or electron energy loss spectroscopy (EELS). Finally, high-resolution electron microscopy in the lateral resolution range of some 0.1 nm allows the reliable geometrical inspection of extreme microregions.     

Beiträge zur Untersuchung anorganischer nichtstöchiometrischer Verbindungen. XLII. Darstellung und elektronenmikroskopische Untersuchung von α-MNb24O62 und MNb52O132 (M = Zr,Hf)

Contributions to the Investigation of Inorganic Non-Stoichiometric Compounds. XLII. Preparation and Electron Microscopic Investigation of α-MNb₂₄O₆₂ and MNb₅₂O₁₃₂ (M = Zr, Hf) The new ternary oxides α-HfNb₂₄O₆₂ and HfNb₅₂O₁₃₂ were obtained by oxidizing corresponding mixtures of HfO₂/NbO₂ and subsequent heating at 1150°C, a temperature which is unusually low for reactions in this system. In contrast, α-ZrNb₂₄O₆₂ could not be obtained in this way. Instead, samples with a certain amount of this compound were synthesized in a manner described previously, but they always contained considerable amounts of the β-Modification, too. HRTEM-investigations showed all compounds, mentioned above, to have block structures. The ideal structure of HfNb₅₂O₁₃₂ corresponds to the wellknown NbO_x?phase Nb₅₃O₁₃₂; α-ZrNb₂₄O₆₂ and α-HfNb₂₄O₆₂ are isostructural to Nb₂₅O₆₂. Additionally, there exist corresponding relationships to TiNb₅₂O₁₃₂ and TiNb₂₄O₆₂. Samples with a starting composition of ZrO₂/NbO₂ = 1:24 were microheterogenous and contained large amounts of the hybrid phase ZrNb₃₈O₉₇.     

非水纳米分散系的冷冻蚀刻电镜原位观测

研究了冷冻蚀刻电镜技术原位观测合成的纳米分散系的制样步骤、制样方法,并利用冷冻蚀刻电镜技术原位观测了四种纳米分散系中分散相的粒度、粒度分布和聚集状态.研究结果表明:蚀刻时间对电镜照片图像质量有较大影响,蚀刻时间应根据分散系中分散相含量、粒度大小来选;冷冻蚀刻电镜用于原位观测非水纳米分散系,具有准确、直观、清晰、立体的特点,并且可同时采集多种信息.     

Spectroscopies and Electron Microscopies Unravel the Origin of the First Colour Photographs

The first colour photographs were created by a process introduced by Edmond Becquerel in 1848. The nature of these photochromatic images colours motivated a debate between scientists during the XIX^th century, which is still not settled. We present the results of chemical analysis (EDX, HAXPES and EXAFS) and morphology studies (SEM, STEM) aiming at explaining the optical properties of the photochromatic images (UV‐visible spectroscopy and low loss EELS). We rule out the two hypotheses (pigment and interferences) that have prevailed since 1848, respectively based on variations in the oxidation degree of the compound forming the sensitized layer and periodically spaced photolytic silver planes. A study of the silver nanoparticles dispersions contained in the coloured layers showed specific localizations and sizes distributions of the nanoparticles for each colour. These results allow us to formulate a plasmonic hypothesis on the origin of the photochromatic images colours.     

Spectroscopies and Electron Microscopies Unravel the Origin of the First Colour Photographs

The first colour photographs were created by a process introduced by Edmond Becquerel in 1848. The nature of these photochromatic images colours motivated a debate between scientists during the XIX^th century, which is still not settled. We present the results of chemical analysis (EDX, HAXPES and EXAFS) and morphology studies (SEM, STEM) aiming at explaining the optical properties of the photochromatic images (UV-visible spectroscopy and low loss EELS). We rule out the two hypotheses (pigment and interferences) that have prevailed since 1848, respectively based on variations in the oxidation degree of the compound forming the sensitized layer and periodically spaced photolytic silver planes. A study of the silver nanoparticles dispersions contained in the coloured layers showed specific localizations and sizes distributions of the nanoparticles for each colour. These results allow us to formulate a plasmonic hypothesis on the origin of the photochromatic images colours.     

Imaging in the modern age

This report of the 2011 James L. Waters Symposium at Pittcon 2011 highlights the powerful imaging technologies of electron microscopy (EM) and ion microscopy (IM). The four speakers each provided a window into a specific subset of the field:

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David Bell described the history, development, application, and commercialization of transmission EM (TEM) and scanning TEM (STEM);

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David Martin presented the challenges and methodologies of imaging ordered polymers and biomaterials with TEM;

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Joseph Michael explained the history of the commercialization of scanning EM (SEM) and its modern applications; and,

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David Joy, who submitted his talk in absentia, provided a history of EM and a summary of the advantages of IM versus EM.

     

基于透射电子显微镜的沸石分子筛结构研究进展

透射电子显微镜是解析沸石分子筛新结构、 分析结构缺陷和研究活性位点等的有力工具. 应用于分子筛研究的透射电子显微术总体上可以分为图像法和衍射法, 包括透射电子显微镜和扫描透射电子显微图像、 选区电子衍射和三维电子衍射, 通常结合其中的几种方法进行分析. 近年来, 随着电子显微镜硬件性能的不断提升, 特别是球差矫正器的广泛应用及各种适用于分子筛等电子束敏感材料的探测器和图像处理技术的不断革新, 在原子尺度观察分子筛的结构已成为可能. 此外, 利用原位电子显微镜技术研究分子筛的生长和催化反应机理也在逐步展开. 本文按电子显微镜方法分类, 综述了近些年基于电子显微镜的分子筛研究, 包括新结构解析、 手性确认和金属负载等的最新进展.     

Electron microscopy of submicron particles in natural waters—Morphology and elemental analysis of particles in fresh waters

Submicron particles larger than about 0.1m in pond and river waters were collected on a carbon film mounted on a specimen grid by centrifugation and then studied morphologically and analyzed for major elements heavier than sodium, with a high-resolution transmission electron microscope equipped with an energy dispersive X-ray analyzer. If available, the data were compared with those of particles artificially prepared under various conditions. Four typical particles—aluminosilicate, quartz, fine-particle aggregates containing silica and iron(III) oxide, and microorganisms—were found in fresh waters.