Progress in the toxicological researches for quantum dots

Quantum dots (QDs) have received more and more attention as a novel example of nanomaterials. Due to their unique fluorescent characteristics, quantum dots have been successfully applied in biotechnology and medicine applications. Recently, the toxicity and the potential environmental effects of QDs have become a research hotspot. In this paper, toxicological effects of QDs are reviewed, and the prospects and research directions are given based on the analysis of this research field

Controllable DNA Condensation-Release Induced by Simple Azaheterocyclic-Based Metal Complexes

The condensation of DNA is essential for biological processes such as DNA transcription and replication, and its study receives additional impetus from an interest in gene therapy. Although many efficacious condensing agents have been discovered and investigated, little is known about the conversation of condensation-release under suitable conditions. A novel class of DNA condensing agents based on small azaheterocyclic metal-binding molecules has been discovered and described. Both linear and plasmid DNA can be condensed to nanoparticles by the title compounds with 50 degrees C incubation, especially in the presence of divalent metal ions. Importantly, this condensation may be released to original forms with little or no damage to the DNA under incubation at physiological temperatures. These changes in DNA morphology over time have been analyzed by gel electrophoresis, circular dichroism (CD), and atomic force microscopy (AFM). The present work might help to develop strategies for the design and synthesis of controllable condensing agents, which may also be applied to control gene expression and delivery.National Nature Science Foundation of China[20732004, 20872010, 20972014, 21172016

One-step immunochromatographic separation and ELISA quantification of glycyrrhizin from traditional Chinese medicines

The bioactive constituent, glycyrrhizin or glycyrrhizic acid (GA), was purified from two traditional Chinese medicines (TCM), Shaoyao gancao tang and Dahuang gancao tang, and from crude extracts from licorice roots by means of immunoaffinity chromatography using anti-GA monoclonal antibody (MAb) and was quantified with an enzyme-linked immunosorbent assay (ELISA). Laboratory preparations included the synthesis of conjugate GA-human serum albumin (GA-HSA), the production of anti-GA-MAb, the optimization of the immunoaffinity column packed with the anti-GA-MAb coupled to hydrazide gel and the determination of the GA content in TCM and crude drugs from five different sources by ELISA and high performance liquid chromatography (HPLC). The experimental results reveal that the anti-GA-MAb coupled to Affi-Gel Hz gel results in a coupling efficiency of 95.2%, and the immunoaffinity chromatography gives a mean recovery of 97.6% of GA with a capacity of 33.5 +/- 2.40 mu g/mL of immunoaffinity gel under the given conditions. The GA content of the crude extracts (ranging 74.8-114.6 mu g/mg) from different sources by the ELISA method is much greater than that of the TCM (16.4-25.1 mu g/mg) which is, in good agreement with the results of the HPLC method. Our report provides a rapid, reliable and sensitive approach for one-step separation and quantification of GA. (c) 2006 Elsevier B.V. All rights reserved

Molecular structural and functional characterization of STAT1 gene regulatory region in teleost Channa argus

The transcription factor STAT1 is involved in signal transduction of type I and II interferons (IFNs). However, the molecular characteristics of the STAT1 regulatory region still remain to be elucidated in teleosts. In the present study, the complete cDNA and the regulatory region of the STAT1 gene were isolated from snakehead (Channa argus). More than 2.4 kb 5'-flanking region of STAT1 shares the regulatory elements of IFN-stimulated response element (ISRE) and IFN-gamma activation site (GAS). Consensus ISRE and GAS were located from -373 to -361 and -716 to -724 in the promoter region, respectively. Moreover, it is noticeable that the crucial elements of ISRE (+698 to +710) and GAS (+294 and +301) are present in the first intron of snakehead STAT1. Comparisons of six vertebrate STAT1 5'-flanking regions all present the common sequence characteristics of IFN-induced gene promoter, which include ISRE, GAS and Sp1 sites. In order to further characterize the snakehead STAT1 regulatory region, six reporter constructs of snakehead STAT1 promoter and first intron were generated to examine the specificity to human interferon-gamma (hIFN-gamma). Only those constructs containing the ISRE element showed notable reporter activity after stimulation of Hela cells with hIFN-gamma. However, sequential deletions of putative transcription factor binding sites indicated that GAS elements have little effect on the promoter and intronic activity in response to hIFN-gamma. Taken together, these results suggest that the regulatory mechanisms of IFN-signalling appear to be mediated in a similar manner in fish and mammals. (C) 2009 Elsevier B.V. All rights reserved

DNA damage induced by shikonin in the presence of Cu(II) ions: potential mechanism of its activity to apoptotic cell death

Shikonin (beta-alkannin), a naphthazarin derivative, has shown a variety of abilities such as anti-inflammatory, antitumoral, cytotoxic, and antimicrobial activities. In the presence of Cu(II), shikonin caused breakage of supercoiled plasmid pBR322 DNA. Other metal ions tested [Mg(II), Ca(II), and Ni(II)] were ineffective and only Fe(II) has the same ability in the DNA breakage reaction. The involvement of active oxygen in the reaction was established by the inhibition of DNA breakage by superoxide dismutase, catalase, thiourea, sodium azide, potassium iodide, and sodium benzoate. Cu(I) was shown to be an essential intermediate using the Cu(I)-specific sequestering reagent neocuproine. Shikonin induced HeLa cell apoptosis involved in the mechanism of increasing intracellular reactive oxygen species (ROS). It was suggested that shikonin generated ROS as a pro-oxidant in the presence of Cu(II), and ROS resulted in DNA damage and apoptotic cell death in cells.National Natural Science Foundation of China[20732004]; Natural Science Foundation of Fujian Province, China[2009J01192

Electrochemical synthesis and optical properties of helical polyaniline nanofibers

Helical polyaniline (PANI) nanofibers were facilely synthesized via a direct electrochemical method without using any template in the presence of (1S)-(+)-camphor-10-sulfonic acid (D-CSA) or (1R)-(-)-camphor-10-sulfonic acid (L-CSA) as the dopant. The helical morphologies of the PANI nanofibers prepared from potentiostatic deposition were confirmed with SEM and TEM. The helical PANI nanofibers induced by D-CSA and L-CSA exhibited mirror-imaged circular dichroism spectra in the UV-vis range, indicating the stereochemical selectivity of the electrochemical polymerization. The colors and optical activities of these nanofibers can be maintained on an indium-tin oxide (ITO) coated electrode with a dedoping/redoping treatment. The optical activities of the helical PANI nanofibers reversibly varied with different oxidized forms, which were easily controlled by the different potentials applied to the nanofibers. (C) 2009 Elsevier Ltd. All rights reserved.National Natural Science Foundation of China [20433040, 20423002]; State Key Laboratory for Physical Chemistry of the Solid Surface (Xiamen University

Phytoplankton-zooplankton dynamics vary with nutrients: a microcosm study with the cyanobacterium Coleofasciculus chthonoplastes and cladoceran Moina micrura

Anti-grazer responses of phytoplankton have been widely documented to vary with external abiotic factors (e. g. nutrient status), suggesting an environment-dependence of phytoplankton-zooplankton dynamics. Here, we examined the trophic interaction between the cyanobacteria Coleofasciculus chthonoplastes and the cladoceran Moina micrura under three nutrient levels from oligotrophic to hypereutrophic conditions (0.3, 3.0 and 100.0 mu M PO43-; molar ratio NO3- : PO43- - 16 : 1) to determine the effect of nutrients on the stability of a phytoplankton-zooplankton system. In the absence of M. micrura, cell density and filament (single-filament) length of C. chthonoplastes were lower at the low nutrient level compared with those at the medium and high nutrient levels. When M. micrura was present, cell density, filament length, colony proportion and size (the mean number of cells per colony) of C. chthonoplastes were highest under the medium nutrient level, corresponding to the lowest amplitude of density fluctuations in M. micrura. Regression analyses revealed that low cell densities of C. chthonoplastes (due to its limited ability to form colonies and long filaments and hence a high consumption rate of M. micrura) at low and high nutrient levels limited the growth of M. micrura adult females, leading to a sharp decline in embryo length, clutch size and population density. In general, our results suggest that the stability of phytoplankton-zooplankton systems varies with nutrients because of the nutrient-dependent morphology in phytoplankton, and imply that extremely low or high nutrient load may destabilize phytoplankton-zooplankton systems