Abstract This work describes a novel and scalable colloid chemistry strategy to fabricate gold semishells based on the selective growth of gold on Janus silica particles (500 nm in diameter) partly functionalized with amino groups. The modulation of the geometry of the Janus silica particles allows us to tune the final morphology of the gold semishells. This method also provides a route to fabricating hollow gold semishells through etching of the silica cores with hydrofluoric acid. The optical properties were characterized by visible near‐infrared (vis‐NIR) spectroscopy and compared with simulations performed using the boundary element method (BEM). These revealed that the main optical features are located beyond the NIR region because of the large core size.
Environmental context. Dissolved organic matter protects aquatic microorganisms from toxic metals by complexing and decreasing the concentration of the biologically reactive species such as free metal ions. However, there are some cases of enhancement of toxic effects when humic acids are present, which is thought to be due to effects of adsorbed humic acids on cell membranes. For a marine diatom, humic acids adsorbed to cell surfaces enhanced metal adsorption, whereas intracellular metal contents decreased as a result of metal binding by humic acids. These findings suggest that the diatom wall, the frustule, presents a barrier against direct effects of adsorbed humic acids on the plasma membrane. Abstract. Metal complexation by dissolved organic matter, as humic acids, is considered to decrease metal bioavailability by lowering the free metal ion concentration. However, dissolved organic matter adsorption on cell surfaces can modify cell membrane properties, which can also influence metal uptake. Copper and lead accumulation and internalisation by the marine diatom Thalassiosira weissflogii were studied in the absence and presence of humic acids, and adsorption of humic acids to cell surfaces was evaluated. Both Pb and Cu intracellular concentrations decreased in the presence of humic acids according to labile metal concentrations measured by anodic stripping voltammetry, whereas total (intracellular plus adsorbed) metal content was enhanced in the presence of humic acids, probably owing to enhanced metal plus humics adsorption to cell surfaces. The results of the present work stress the importance of differentiating between intracellular and total cellular metal in bioavailability studies, and suggest that the silica frustule of diatoms represents a barrier against humic acids effects on cell membranes.
The environmental monitoring strategy termed ecosystem-based approach (EBA) underlines the obvious benefits of managing natural resources on a holistic level, and it is particularly invoked for the rational and sustainable management of aquatic resources. However, when coming to implement EBA into monitoring schemes, such as those derived from the implementation of the European legislation concerning water quality, difficulties inherent to the complex and dynamic nature of ecosystems arise, including (i) identify appropriate, relevant and easily measurable indicators of ecosystem integrity, and (ii) combine the heterogeneous information gathered at the different levels of organization included in an ecosystem into a simple and practical decision-making scheme. The first kind of difficulties maybe partially overcome by implementing monitoring schemes which take into account the hierarchical nature of ecosystem processes and did not neglect the use of indicators at low levels of biological organization, including ecotoxicological biomarkers and bioassays. Secondly, the integration of the monitoring results into a practical decision-making scheme can best be achieved by using non metric multivariate analysis, which is especially suitable for data bases including different metrics, and allows the processing of variables showing non-monotonic response to human stress, from molecular biomarkers to community indices. The difficulties inherent to the current rigid scheme of water quality assessment heavily based on ratio-to-reference univariate indicators and arbitrary reference values and class boundaries for each single indicator are illustrated with a case study in the Minho estuary (NW Iberian Peninsula). The classification of aquatic ecosystems into discrete categories of ecological status can best be achieved by combining observations at different levels of biological organization, from molecular biomarkers to community traits, with explicative physicochemical and hydromorphological elements, and by using non-metric multivariate analysis techniques.
Chemical fungicides can cause drug resistance of plant pathogenic fungi, environmental pollution, and potential threats to humans and animals. Therefore, developing low-toxicity, high-efficient and environment-friendly biological control products is critical for green prevention, controlling plant fungal diseases, and maintaining ecological balance. Biocontrol research mainly includes the following aspects: antagonistic microorganisms, fungicidal proteins, RNA interference techniques and botanical fungicides. Significantly, natural products extracted from medicinal plants are valuable repertoire for inhibiting plant fungal diseases. This review systematically reviewed the research advances of using natural products from medicinal plants to inhibit plant pathogenic fungi, including the types of natural products, extraction methods, and antifungal mechanisms. The further prospects for the study and application, which provide the reference for botanical fungicide development and practical application in preventing and controlling plant fungal disease, were also discussed.
Recently, investigations of biological toxicity of cadmium QDs and their toxic interaction with plasma proteins have attracted great interest. In this work, flavonoids were studied for the affinities for human serum albumin (HSA) in the presence and absence of CdTe G-QDs by fluorescence quenching method. CdTe G-QDs obviously enhanced the binding affinities of kaempferol, genistein and biochanin A by 3.78 to 154.88 times depending on the QDs concentration. However, the affinity of kaempferide for HSA was slightly weakened in the presence of G-QDs. The non-methylated flavonoids were more sensitive to G-QDs than their methylated forms. The affinities of kaempferide and kaempferol for HSA at first were slightly improved and then obviously decreased with increasing G-QDs concentration. For genistein, the affinities for HSA decreased with increasing G-QDs concentration. However, the G-QDs concentration showed no obvious effect on the affinity of biochanin A. The binding affinities of flavonoids for HSA improved with increasing QDs size.
