Amplified DNA detection sensitivity using streptavidin-biotinylated protein complex: Characterization by electrochemical impedance spectroscopy

Thiol-terminated oligonucleotide was immobilized to gold surface by self-assembly method. A novel amplification strategy was introduced for improving the sensitivity of DNA. hybridization using biotin labeled protein-streptavidin network complex. This complex can be formed in a cross-linking network of molecules so that the amplification of the response signal will be realized due to the big molecular size of the complex. It could be proved from the impedance technique that this amplification strategy caused dramatic improvement of the detection sensitivity. These results give significant advances in the generality and sensitivity as it is applied to biosensing.

Arabinogalactan as a carrier for contrast agent in magnetic resonance imaging

Arabinogalactan-Gd-DTPA was synthesized by the reaction of diethylenetriaminepenta-acetic acid (DTPA) bisanhydride with polysaccharide in dry DMSO and characterized by FTIR, elemental analysis and ICP-AES. Its stability was investigated by competition with Ca2+, EDTA, DTPA. The t(1)-relaxivity is 8.06 mmol(-1) . L . s(-1) in D2O, 8.48 mmol(-1) . L . s(-1) in 0.725 mmol . L-1 BSA, respectively. t(1)-weighted MR imaging of rat kidney and liver showed a remarkable enhancement post injection of Arabinogalactan-Gd-DTPA. The results indicate that the arabinogalactan-Gd-DTPA is a potential contrast agent for MRI.

Amplification of antigen-antibody interactions based on biotin labeled protein-streptavidin network complex using impedance spectroscopy

Antibody was covalently immobilized by amine coupling method to gold surfaces modified with a self-assembled monolayer of thioctic acid. The electrochemical measurements of cyclic voltammetry and impedance spectroscopy showed that the hexacyanoferrate redox reactions on the gold surface were blocked due to the procedures of self-assembly of thioctic acid and antibody immobilization. The binding of a specific antigen to antibody recognition layer could be detected by measurements of the impedance change. A new amplification strategy was introduced for improving the sensitivity of impedance measurements using biotin labeled protein- streptavidin network complex. This amplification strategy is based on the construction of a molecular complex between streptavidin and biotin labeled protein. This complex can be formed in a cross-linking network of molecules so that the amplification of response signal will be realized due to the big molecular size of complex. The results show that this amplification strategy causes dramatic improvement of the detection sensitivity of hIgG and has good correlation for detection of hIgG in the range of 2-10 mug/ml. (C) 2001 Elsevier Science B.V. All rights reserved.

Atomic force microscopy imaging of molybdenum oxide film electrodeposited on a carbon electrode

Non-stoichiometric mixed-valent molybdenum(VI, V) oxide film was grown on carbon substrates by the electrodeposition method. Responses of the prepared molybdenum oxide thin films to potential and to different solution acidities were studied by cyclic voltammetry, and the corresponding morphological changes of the film were monitored by atomic force microscopy (AFM). AFM images of the molybdenum oxide film show that the characteristic domed structure on the film surface increased during the transition from the oxidized state to the reduced state without signification change in the KMS surface roughness value. Furthermore, AFM studies show that the solution acidity has great effect on the morphology of the films, and the films undergo a homogenizing process with increasing pH of the solutions. (C) 1999 Elsevier Science S.A. All rights reserved.

A COMPARATIVE-STUDY ON STM IMAGING AND ELECTROCATALYTIC ACTIVITY OF DIFFERENT SURFACES MODIFIED WITH FLAVIN ADENINE-DINUCLEOTIDE

Flavin adenine dinucleotide (FAD) was modified onto the highly oriented pyrolytic graphite (hopg) and glassy carbon electrode (gee) surfaces with three methods, respectively. Corresponding image analysis for FAD-modified hopg surfaces has been performed by scanning tunnelling microscope (STM) for the first time. The molecular resolution STM image of FAD adsorbed on the freshly-cleaved hopg was obtained, the quantitative size determination suggests that the FAD molecules adsorb side lying on the substrate surface. The anodization treatment of hopg surface yields many pits, which were clearly observed under STM. These pits provide active sites on the hopg surface for modification and the treated hopg can strongly adsorb FAD molecules, the latter exhibiting an irregular cluster structure on such a surface. When FAD was electrochemically deposited on the substrate surface, a chain structure was successfully observed. The adsorbed FAD on anodized glassy carbon electrode (gee) surface can effectively catalyze the reduction of glucose oxidase, hemoglobin and myoglobin, with a large decrease in the overvoltage, whereas the deposited FAD film exhibits excellent electrocatalysis towards dioxygen reduction.

HREM IMAGING OF POLY(ARYL-ETHER-KETONE) CRYSTAL

High resolution transmission electron microscope (HREM) was used to observe the rigid chain polymer poly(aryl-ether-ketone) (PEK), so as to study the morphology of the crystals and molecular arrangement within a crystal.Many kinds of material crystal structures have been studied with HREM in recent years. So far as polymeric materials are concerned, the application of HREM

Near-Space Wide-Swath Radar Imaging With Multiaperture Antenna

Near-space, defined as the altitude region between 20 and 100 km, offers many capabilities that are not accessible for low Earth-orbit (LEO) satellites or airplanes because it is above storm and not constrained by orbital mechanics and high fuel consumption. Hence, a high flying speed can be obtained for the maneuvering vehicles operating in near-space. This offers a promising solution to simultaneous high-resolution and wide-swath synthetic aperture radar (SAR) imaging. As such, one near-space wide-swath SAR imaging technique is presented in this letter. The system configuration, signal model, and imaging scheme are described. An example near-space SAR system is designed, and its imaging performance is analyzed. Simulation results show that near-space maneuvering vehicle SAR indeed seems to be a promising solution to wide-swath SAR imaging.

Ocean wave imaging mechanism by imaging radar

Analytical representations of the high frequency spectra of ocean wave and its variation due to the variation of ocean surface current are derived from the wave-number spectrum balance equation. The ocean surface imaging formulation of real aperture radar (RAR) is given using electromagnetic wave backscattering theory of ocean surface and the modulations of ocean surface winds, currents and their variations to RAR are described. A general representation of the phase modulation induced by the ocean surface motion is derived according to standard synthetic aperture radar (SAR) imaging theory. The detectability of ocean current and sea bottom topography by imaging radar is discussed. The results constitute the theoretical basis for detecting ocean wave fields, ocean surface winds, ocean surface current fields, sea bottom topography, internal wave and so on.

SNAP-23蛋白在鲈鱼巨噬细胞白细胞介素1β分泌过程中的功能

SNARE蛋白家族是所有真核细胞胞吐及分泌作用中的关键因子，由其介导的运输囊泡膜与靶膜的锚靠、融合为胞内蛋白的运出提供了一条重要途径。体外试验表明，Syntaxin6-Syntaxin7-Vti1b，SNAP-23-Syntaxin4等SNARE核心蛋白之间精确的相互作用是哺乳动物巨噬细胞肿瘤坏死因子α (TNF-α)运输和分泌的必备条件，在机体非特异性免疫应答反应过程中起重要作用。 本研究受上述启示，旨在揭示SNARE蛋白在海洋鱼类免疫细胞内重要细胞因子白细胞介素1β (IL-1β)的分泌过程中的作用。参照Percoll密度梯度离心技术，从鲈鱼头肾组织分离纯化巨噬细胞进行稳定培养；利用RT-PCR方法克隆出鲈鱼t-SNARE蛋白SNAP-23和Syntaxin3的部分cDNA序列，再结合先前克隆的VAMP2和已知的鲈鱼IL-1β，TNF-α和IL-8的基因序列，设计特异性引物。利用Real-time PCR技术在mRNA水平上精确测定鲈鱼巨噬细胞中上述6种基因在革兰氏阴性菌脂多糖(LPS)分子刺激下的表达变化，发现SNAP-23基因与三种细胞因子基因的表达正相关；通过免疫印迹检测SNAP-23蛋白表达变化，利用酶联免疫吸附试验(ELISA)检测IL-1β的分泌水平，在蛋白水平上验证了SNAP-23表达与IL-1β分泌的正相关性；利用5`RACE和3`RACE技术克隆出鲈鱼SNAP-23全长基因，结合定点突变策略和靶向PCR克隆手段，构建鲈鱼SNAP-23野生型融合质粒pEGFP-SNAP-23wt，Cys缺失突变融合质粒pEGFP-SNAP-23ΔCys和模拟E型肉毒神经毒素(BoNT/E)切割突变融合质粒pEGFP-SNAP-23ΔBoNT/E，以及鲈鱼IL-1β野生型融合表达质粒IL-1β-pEGFP和IL-1β-pEYFP。所有融合蛋白均在鲈鱼巨噬细胞内成功表达，结合ELISA实验结果发现，SNAP-23野生型的表达对IL-1β的分泌有促进作用，而Cys缺失突变体的表达则抑制IL-1β向胞外分泌。首次证实了鱼类巨噬细胞内SNAP-23蛋白在IL-1β分泌过程中的重要作用。此外通过与GFP共表达，定位了IL-1β分子在巨噬细胞内的分布，发现新合成的IL-1β分子很可能像TNFα一样经“内质网－胞质－伪足－胞外” 的分泌路径运出胞外。

Sensitive and Rapid Detection of Genetic Modified Soybean (Roundup Ready) by Loop-Mediated Isothermal Amplification

Using the LAMP method, a highly specific and sensitive detection system for genetically modified soybean (Roundup Ready) was designed. In this detection system, a set of four primers was designed by targeting the exogenous 35S epsps gene. Target DNA was amplified and visualized on agarose gel within 45 min under isothermal conditions at 65 degrees C. Without gel electrophoresis, the LAMP amplicon was visualized directly in the reaction tube by the addition of SYBR Green I for naked-eye inspection. The detection sensitivity of LAMP was 10-fold higher than the nested PCR established in our laboratory. Moreover, the LAMP method was much quicker, taking only 70 min, as compared with 300 min for nested PCR to complete the analysis of the GM soybean. Compared with traditional PCR approaches, the LAMP procedure is faster and more sensitive, and there is no need for a special PCR machine or electrophoresis equipment. Hence, this method can be a very useful tool for GMO detection and is particularly convenient for fast screening.