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The biodistribution and clearance in mice of near-infrared (NIR) ultra-small Ag2Se quantum dots (QDs) were systematically studied. The ICP-MS quantitative assessment and biodistribution fluorescent images of Ag2Se QDs in mouse organs demonstrated that the Ag2Se QDs could be cleared quickly from the mice body mostly by renal excretion without significant long-term organs accumulation. Pathological analysis, blood biochemical analysis, and body weight results also showed that the Ag2Se QDs do not cause appreciable toxicity in vivo. [ABSTRACT FROM AUTHOR]

Abstract: The effects of Li+ and polyethylene glycol (PEG) on the genetic transformation of Saccharomyces cerevisiae were investigated by using fluorescence microscopy (FM) to visualize the binding of plasmid DNA labeled with YOYO-1 to the surface of yeast cells, scanning electron microscopy (SEM) and atomic force microscopy (AFM) to image the change in surface topography of yeast cells, coupled with transformation frequency experiments. The results showed that under the same conditions, the transformation frequencies of yeast protoplasts were much higher than those of intact yeast cells. PEG was absolutely required for the binding of DNA to the surface of intact yeast cells or yeast protoplasts, and had no effect on the surface topography of intact yeast cells or yeast protoplasts. In the presence of PEG, Li+ could greatly enhance the binding of plasmid DNA to the surface of intact yeast cells, increase their transformation frequency, and affect their surface topography. On the other hand, no effect on the DNA binding to the surface of protoplasts and no increase in the number of transformants and no surface topography changes were found upon the treatment with Li+ to protoplasts. In the present work, the effects of Li+ and PEG on yeast genetic transformation were directly visualized, rather than those deduced from the results of transformation frequencies. These results indicate that cell wall might be a barrier for the uptake of plasmid DNA. Li+ could increase the permeability of yeast cell wall, then increase the exposed sites of DNA binding on intact yeast cells. The main role of PEG was to induce DNA binding to cell surface. [Copyright &y& Elsevier]

A strategy is presented that involes coupling Na(2)SeO(3) reduction with the binding of silver ions and alanine in a quasi-biosystem to obtain ultrasmall, near-infrared Ag(2)Se quantum dots (QDs) with tunable fluorescence at 90 °C in aqueous solution. This strategy avoids high temperatures, high pressures, and organic solvents so that water-dispersible sub-3 nm Ag(2)Se QDs can be directly obtained. The photoluminescence of the Ag(2)Se QDs was size-dependent over a wavelength range from 700 to 820 nm, corresponding to sizes from 1.5 ± 0.4 to 2.4 ± 0.5 nm, with good monodispersity. The Ag(2)Se QDs are less cytotoxic than other nanomaterials used for similar applications. Furthermore, the NIR fluorescence of the Ag(2)Se QDs could penetrate through the abdominal cavity of a living nude mouse and could be detected on its back side, demonstrating the potential applications of these less toxic NIR Ag(2)Se QDs in bioimaging., (© 2011 American Chemical Society)

There are four molecules in the asymmetric unit of the title compound, C(16)H(17)N(3)O(4), in which the dihedral angles between the indole ring system and maleimide ring are 4.5 (3), 8.3 (3), 8.4 (2) and 10.4 (2)°. In the crystal, mol-ecules are linked by numerous N-H⋯O and O-H⋯O hydrogen bonds, generating a three-dimensional network.

The culture fluids of Escheriachia coli with shuttle plasmid and Bacillus subtilis strains were mixed and coincubated for 40 minutes after culturing respectively in LB and minimal media. The steadily plasmid transfer by natural genetic transformation between these two gram-negative and gram-positive bacteria has been demonstrated by the methods of selective medium screening, DNase I sensitivity test and plasmid detection. In contrast to MM culture B. subtilis LB culture can be competent and has equivalent transformation frequency. Furthermore, the maximal transformation frequency was obtained when cells in exponential phase served as donors or recipients. It is suggested that B. subtilis solid transformation is different from liquid plasmid transformation including the whole process of DNA plasmid competence producing. Understanding the mechanisms of gene transfer between bacteria may aid in assessing the potential risk associated with the release of recombinant organisms into the environment.

Strain sp-f was isolated, a siderophores over producing bacterium, using an improved universal Chrome Azurol S(CAS)-agar plate method from Donghu Lake. The result of the CAS solution siderophores quantitative determination showed the lowest As/Ar (OD680) ratio could be as low as 0.09 with Su (Siderophore Unit) of 90%. Some more experiments were made to make out the pertinence between its growth and siderophores production, indicating that its siderophores quantity reached maximum amount during the prophase of logarithmic growth. After then, siderophores concentration stopped accumulating and turned to be stable at stationary phase. Based on the characteristics of morphology, cultivation, physiology, (G + C) mol % content, 16S rDNA sequence and BIOLOG Station system analysis, it was identified as Pseudomonas fluorescens sp-f strain. RP-HPLC analysis showed there exist at least 3 kinds of catecholate siderophores, including fluorescent and non-fluorescent pyoverdins. But only fluorescent pyoverdin's excretion was completely repressed by the 200 micromol/L Fe2+ in the medium. And the non-pyoverdin siderophores excretion was induced at the same time, contrarily.

Semiconductor quantum dots (QDs) as a kind of nonisotopic biological labeling material have many unique fluorescent properties relative to conventional organic dyes and fluorescent proteins, such as composition- and size-dependent absorption and emission, a broad absorption spectrum, photostability, and single-dot sensitivity. These properties make them a promising stable and sensitive label, which can be used for long-term fluorescent tracking and subcellular location of genes and proteins. Here, a simple approach for the construction of QD-labeled DNA probes was developed by attaching thiol-ssDNA to QDs via a metal-thiol bond. The as-prepared QD-labeled DNA probes had high dispersivity, bioactivity, and specificity for hybridization. Based on such a kind of probe with a sequence complementary to multiple clone sites in plasmid pUC18, fluorescence in situ hybridization of the tiny bacterium Escherichia coli has been realized for the first time.

In this paper the conception of horizontal gene transfer (HGT) was introduced,and main mode of HGT was also enumerated as follows: HGT by medium such as plasmid and virus etc., and the HGT without any medium. The transfer of genes from one species to another especially between remote species was emphasized by the information from genome sequencing. The problems about evolution phylogenies and safety of GEMs (gene engineered microorganisms) for HGT were discussed.

Chinese sucker, Myxocyprinus asiaticus, is an endemic species of China and also the only representatives of family Catostomidae in Asia. The fish was naturally distributed in Yangtze River and Mingjiang River and now few could be captured because of pollution and overexploitation. The fish has been listed in the second class of preserved animal in China. Studying and assessing its population structure is an imperative and fundamental work for making effective protection strategies. We amplified and sequenced the D-loop region of mtDNA of 8 samples. The size of the D-loop region is about 958 bp. A total of 32 variation loci were detected and the mutation rate was 0.033. All the mutation came from nucleotide substitution except one nucleotide deletion. Most of the nucleotide variations were found between the 55-365 bp region. The individual mutation rate varied from 0-1.36%, which exhibited nucleotide polymorphism to some extent among 8 samples. Compared with RAPD and other PCR-based methods, the directily sequencing of mtDNA D-loop region revealed much more genetic diversity. Meanwhile, the D-loop region of Moxostoma robustum derived from GenBank was aligned with that of Chinese sucker through CLUSTAL software. By comparison, we found that the mutation rate (0.033) of D-loop of Chinese sucker is higher than that of Moxostoma robustum (0.016).