Effect of DNA and bivalent metal ions on the interaction of thermostable DNA polymerase <Emphasis Type="Italic">Tte</Emphasis> with dNTPs

The interaction of DNA polymerase Tte from Thermus thermophilus B35 with dUTP analog containing a fluorescein residue bound to C(5) of the base (Flu-dUTP) was studied by fluorescence titration. The dissociation constants of the enzyme—substrate complexes in the absence and in the presence of a DNA duplex containing an extended template and bivalent metal ions and the kinetic parameters of polymerization by DNA polymerase Tte in the presence of Flu-dUTP were determined. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1268–1272, May, 2005.     

Siderophore production by a marine Pseudomonas aeruginosa and its antagonistic action against phytopathogenic fungi

A marine isolate of fluorescent Pseudomonas sp. having the ability to produce the pyoverdine type of siderophores under low iron stress (up to 10 μM iron in the succinate medium) was identified as Pseudomonas aeruginosa by using BIOLOG Breathprint and siderotyping. Pyoverdine production was optimum at 0.2% (w/v) succinate, pH 6.0, in an iron-deficient medium. Studies carried out in vitro revealed that purified siderophores and Pseudomonas culture have good antifungal activity against the plant deleterious fungi, namely, Aspergillus niger, Aspergillus flavus, Aspergillus oryzae, Fusarium oxysporum, and Sclerotium rolfsii. Siderophore-based maximum inhibition was observed against A. niger. These in vitro antagonistic actions of marine Pseudomonas against phytopathogens suggest the potential of the organism to serve as a biocontrol agent.     

Permeation associated with three-phase-partitioning method on release of green fluorescent protein

Transformed cells of Escherichia coli expressing recombinant green fluorescent protein (GFPuv) were subjected to two methods of extraction: (1) freezing/thawing/sonication (FTS) cycles prior to the three-phase partitioning (TPP) method, or (2) directly to TPP extraction. The amount of GFPuv released by the FTS plus TPP method varied: 374μg/mL (first cycle), 93–442 μg/mL (second cycle), 32–359 μg/mL (third cycle), 18–115 μg/mL (fourth cycle). The GFPuv yields by the second method (TPP only) were, 23–54 μg/mL for the first extract and 33–91 μg/mL for the second. The FTS plus TPP method released similar amounts of GFPuv to that extracted by TPP; and provided a better mixture elution through the hydrophobic interaction column: 13–63 μg/mL for FTS plus TPP methods, and 2.5–13 μg/mL for TPP. The results showed that although selective permeation is a more laborious methodology, it was more efficient for obtaining of GFPuv in relation to the direct extraction of the cells for TPP.     

Structural, spectroscopic and photoluminescence studies of LiEu(WO4)2−x(MoO4)x as a near-UV convertible phosphor

A series of lithium europium double tungsto-molybdate phosphors LiEu(WO₄)_2−x(MoO₄)_x (x=0, 0.4, 0.8, 1.2, 1.6, 2.0) have been synthesized by solid-state reactions and their crystal structure, optical and luminescent properties were studied. As the molybdate content increases, the intensity of the ⁵D₀→⁷F₂ emission of Eu³⁺ activated at wavelength of 396 nm was found to increase and reach a maximum when the relative ratio of Mo/W is 2:0. These changes were found to be accompanied with the changes in the spectral feature, which can be attributed to the crystal field splitting of the ⁵D₀→⁷F₂ transition. As the molybdate content increases the emission intensity of the 615 nm peak also increases. The intense red-emission of the tungstomolybdate phosphors under near-UV excitation suggests them to be potential candidate for white light generation by using near-UV LEDs. In this study the effect of chemical compositions and crystal structure on the photoluminescent properties of LiEu(WO₄)_2−x(MoO₄)_x is investigated and discussed.     

SNAP-tag蛋白标签技术与荧光分析法在蛋白原位分析中的联合应用

为将生物体内微观的蛋白行为可视化并以宏观信号呈现出来对蛋白进行实时、动态分析，借助SNAP-tag蛋白标签技术与有机小分子荧光染料，构建了一系列用于活细胞内实时监测目标蛋白的免洗荧光探针。标签蛋白SNAP-tag能够特异性识别探针中的苄基鸟嘌呤，从而使目标蛋白共价连接上荧光团（萘酰亚胺），携带上荧光信使。此外，由于萘酰亚胺从水环境中被牵引至SNAP-tag蛋白的疏水空腔，其荧光信号呈现出2~13倍的增强。通过SNAP-tag标签蛋白与目标蛋白的融合，该荧光探针实现了对活细胞内线粒体蛋白CoX8A及核内蛋白H2B特异性识别，在免洗条件下完成了对目标蛋白的实时追踪及原位分析。     

5-氨基-1,10-菲咯啉：可异构化杂环螯合荧光载体作为比例计量型锌离子荧光探针的一种原型

5-amino-l,10-phenanthroline （5-AP）, as a tautomeric heterocyclic aromatic chelating fluorophore （THACF）, can sense Zn^2＋ selectively by shifting emission from 495 to 564 nm upon Zn^2＋ addition in ethanol. The ratiometric fluorescent sensing behavior has been correlated to the tautomerization of 5-AP affected by solvents and metal chelation. The strategy using THACF as ratiometric fluorescent sensor for Zn^2＋ not only simplifies the synthetic procedure but also gives a promising alternative for Zn^2＋ ratiometric fluorescent sensor design.     

甾醇边链的化学修饰

本文对近年来甾醇边链结构改造的新方法和新动向--Barton 的Gif系统氧化反应及Breslow的远程功能化反应进行了综述。     

Real-time measurement of nitric oxide using a bio-imaging and an electrochemical technique

Nitric oxide (NO) is an important mediator responsible for numerous physiological phenomena. Transient levels of NO in biological systems usually range from nanomolar to micromolar concentrations, with a rapid return to basal levels normally seen following these increases. Because NO can diffuse only over a local area in limited time due to such low levels of production and due to its short life-time prior to degradation, high spatial and temporal resolutions are required for direct and continuous NO measurement if the physiological role of NO is to be investigated in any system. For such purposes, analytical methods based on bio-imaging and electrochemical techniques for the measurement of NO are useful. In this paper, we describe the successful application of these methods to a number of biological systems. Specifically, complementary application of these methods demonstrate that it is possible to detect real-time NO production from nervous tissue with high spatial and temporal resolutions.     

Fluorescent Molecular Recognition and Sensing System of Bis-Dansyl Modified γ-Cyclodextrins

Flexible hosts, 6A,6B-; 6A,6C-; 6A,6D-; and 6A,6E-bis dansylglycine-modified -cyclodextrins (-1, -2, -3, and -4, respectively) have been synthesized as a sensing molecule for organic guests including terpenoids and bile acids. These host compounds show a pure monomer fluorescence whose intensity is decreased or enhanced upon addition of guest species. The value I/I₀, where I and I₀ are fluorescence intensities in the presence and absence of a guest and I is I₀- I, was used as a parameter of sensitivity. These hosts exhibit highly sensitive and selective molecular recognition ability, particularly, for lithochoic acid, chenodeoxycholic acid, and ursodeoxycholic acid. The behaviors of the appended moieties of these hosts when host–guest complexation occurs are studied by induced circular dichroism (ICD) spectra and fluorescence spectral change on accommodation of a guest. The ICD pattern of these hosts alone or on accommodation of a guest is very similar, indicating that the behavior of the appended moieties are very similar. The guest-induced variations in the fluorescence or ICD intensity suggest that the appended moieties act as a hydrophobic cap that enables the cyclodextrin to form 1 : 1 host–guest complexes.     

三芳基咪唑类化合物的合成及其双光子吸收性能研究

双光子吸收是指物质分子或原子在强激光激发下同时吸收两个光子,从基态跃迁到两倍光子能量激发态的过程。目前,双光子吸收材料已广泛地应用到双光子激发显微[1]、频率上转换激射[2-3]、光学限幅、三维光信息存储[4]以及光生物学等领域。但在已报道的双光子诱导上转换荧光的有机