Enhanced fluorescence of tetrasulfonated zinc phthalocyanine by graphene quantum dots and its application in molecular sensing/imaging

When excited at 435 nm, tetra‐sulfonate zinc phthalocyanine (ZnPcS₄) emitted dual fluorescence at 495 and 702 nm. The abnormal fluorescence at 495 nm was experimentally studied and analyzed in detail for the first time. The abnormal fluorescence at 495 nm was deduced to originate from triplet–triplet (T–T) energy transfer of excited phthalocyanine (³*ZnPcS₄). Furthermore, graphene quantum dots (GQDs) enhanced the 495 nm fluorescence quantum yield (Q) of ZnPcS₄. The fluorescence properties of ZnPcS₄–GQDs conjugate were retained in a cellular environment. Based on the fluorescence of ZnPcS₄–GQDs conjugate, we designed and prepared an Apt29/thrombin/Apt15 sandwich thrombin sensor with high specificity and affinity. This cost‐saving, simple operational sensing strategy can be extended to use in sensing/imaging of other biomolecules.     

Magnesium transport and function in plants: the tip of the iceberg

The maintenance of Mg²⁺ homeostasis in the plant is essential for viability. This review describes Mg²⁺ functions and balancing in plants, with special focus on the existing knowledge of the involved transport mechanisms. Mg²⁺ is essential for the function of many cellular enzymes and for the aggregation of ribosomes. Mg²⁺ concentrations also modulate ionic currents across the chloroplast and the vacuolar membranes, and might thus regulate ion balance in the cell and stomatal opening. The significance of Mg²⁺ homeostasis has been particularly established with regard to Mg²⁺'s role in photosynthesis. Mg²⁺ is the central atom of the chlorophyll molecule, and fluctuations in its levels in the chloroplast regulate the activity of key photosynthetic enzymes. Relatively little is known of the proteins mediating Mg²⁺ uptake and transport in plants. The plant vacuole seem to play a key role in Mg²⁺ homeostasis in plant cells. Physiological and molecular evidence indicate that Mg²⁺ entry to the vacuole is mediated by Mg²⁺/H⁺ exchangers. The Arabidopsis vacuolar Mg²⁺/H⁺ exchanger, AtMHX, is highly transcribed at the vascular tissue, apparently most abundantly at the xylem parenchyma. Inclusion of Mg²⁺ ions into the vacuoles of this tissue may determine their partitioning between the various plant organs. Impacts of Mg²⁺ imbalance are described with respect for both plant physiology and for its nutritional value to animal and human.     

四种景天属植物对锌吸收和累积差异的研究

采用营养液培养试验 ,比较研究了 4种景天属植物对Zn的吸收、积累和运输特性。结果表明 ,东南景天(SedumalfrediiHance)耐Zn毒的能力远强于珠芽景天 (S .sarmentosumBunge)、凹叶景天 (S .bulbiferumMakino)和垂盆草 (S .emarginatumMigo) ,其地上部和根系的干物质产量随着Zn浓度的增加而逐渐减少 ;当浓度≤ 40mg·L-1时 ,东南景天的地上部和根系的干物质产量均随Zn浓度的增加而增加 ,其地上部Zn含量、积累量及其Zn运输速率均显著高于珠芽景天、凹叶景天和垂盆草 ;当Zn浓度低于 80mg·L-1时 ,东南景天地上部Zn含量随着营养液中Zn浓度的增加而增加 ,在 80mg·L-1浓度 ,其地上部Zn含量高达 19.0 9mg·g-1。东南景天的地上部Zn含量 /根系Zn含量的比值大于 1,而株芽景天、凹叶景天和垂盆草的地上部Zn含量 /根系Zn含量比值小于 1。东南景天是在我国首次发现的具有生物量大、生长速率快的一种新的Zn超积累植物     

Preconcentration and separation of copper, zinc and cadmium by the use of 6-mercapto purinylazo resin and their application in microwave digested certified biological samples followed by AAS determination of the metal ions

6-Mercapto purinylazo resin has been used as solid phase extractor. Based on solid phase extraction, the present work describes the preconcentration and determination of copper, zinc and cadmium in certified biological samples after microwave-assisted digestion. The exchange capacity of the resin, the sorption and desorption of metal ions, and the effect of diverse ions have also been determined. The results show that the resin is highly selective for determination of these biologically significant metals. The method is simple, rapid and free from interferences and can be used routinely.     

Accumulation, depuration and distribution of cadmium and zinc in the green-lipped mussel Perna viridis (Linnaeus) under laboratory conditions

Ecotoxicological tests were conducted in the green-lipped mussel Perna viridis under laboratory conditions. Different rates of accumulation and depuration in soft tissues are found and this might be due to different mechanisms of metal binding and regulation. At the end of depuration, Cd levels in soft tissues of P. viridis were 10–30 times higher than before exposure, while Zn levels in soft tissues were almost similar to levels before exposure. These results indicate that P. viridis is a good biomonitoring organism for Cd but Zn levels might be actively regulated. It remains uncertain whether P. viridis is a good biomonitoring organism of environmental Zn contamination. However, the positive patterns, although different rates, of accumulation and depuration for Cd and Zn support the use of P. viridis as a biomonitoring agent for such metals.     

Effects of Chronic Waterborne and Dietary Metal Exposures on Gill Metal-Binding: Implications for the Biotic Ligand Model

The biotic ligand modeling (BLM) approach has gained recent widespread interest among the scientific and regulatory communities because of its potential for developing ambient water quality criteria (AWQC), which are site-specific, and in performing aquatic risk assessment for metals. Currently, BLMs are used for predicting acute toxicity (96?h LC50 for fish) in any defined water chemistry. The conceptual framework of the BLM has a strong physiological basis because it considers that toxicity of metals occurs due to the binding of free metal ions at the physiologically active sites of action (biotic ligand, e.g., fish gill) on the aquatic organism, which can be characterized by conditional binding constants (log K) and densities (B_max). At present, these models assume that only water chemistry variables such as competing cations (e.g., Na⁺, Ca²⁺, Mg²⁺, and H⁺), inorganic ligands (e.g., hydroxides, chlorides, carbonates), and organic ligands (dissolved organic matter) can influence the bioavailability of free metal ions and thereby the acute toxicity of metals. Current BLMs do not consider the effects of chronic history of the fish in modifying gill-metal binding characteristics and acute toxicity. Here, for Cu, Cd, and Zn, we review a number of recent studies on the rainbow trout that describe significant modifying effects of chronic acclimation to waterborne factors (hardness and chronic metal exposure) and dietary composition (metal and essential ion content) on gill metalbinding characteristics (on both log K and B_max) and on acute toxicity. We conclude that the properties of gill-metal interaction and toxicological sensitivity appear to be dynamic rather than fixed, with important implications for further development of both acute and chronic BLMs. Now that the initial framework of the BLM has been established, future research needs a more integrative approach with additional emphasis on the dynamic properties of the biotic ligand to make it a successful tool for ecological risk assessment of metals in the natural environment.     

An Ecological Risk Assessment of Air Emissions of Trace Metals from Copper and Zinc Production Facilities

Trace metals are components of releases to air emitted by copper and zinc production facilities in Canada. Six metals (copper, zinc, nickel, lead, cadmium, and arsenic) are examined as part of an overall environmental assessment of these releases. Estimates of metal deposition rates to soils and surface waters were derived from monitoring data in the vicinity of the production facilities and also through dispersion modelling studies. Fate and transport modelling of the metals deposited allowed an estimation of critical loads. Estimated annual deposition rates were compared with 25^th-percentile critical loads typically representative of effects on sensitive organisms under 25% of conditions in sandy soils or circumneutral to acidic lake waters. The results of the comparison suggest that there is a potential for adverse effects on aquatic and/or soil-dwelling organisms from exposure to steadystate concentrations of metals in the vicinity of copper and zinc production facilities. Approaches of particular significance in these assessments include probabilistic estimation of critical loads for metals, allowance for the speciation of metals defining the bioavailable fraction and limiting critical effect levels to the high end of natural background metal concentrations.     

Genetic basis of Cd tolerance and hyperaccumulation in Arabidopsis halleri

The genetic basis of Cd tolerance and hyperaccumulation was investigated in Arabidopsis halleri. The study was conducted in hydroponic culture with a backcross progeny, derived from a cross between A. halleri and a non-tolerant and non-accumulating related species Arabidopsis lyrata ssp. petraea, as well as with the parents of the backcross. The backcross progeny segregates for both cadmium (Cd) tolerance and accumulation. The results support that (i) Cd tolerance may be governed by more than one major gene, (ii) Cd tolerance and Cd accumulation are independent characters, (iii) Cd and Zn tolerances co-segregate suggesting that they are under pleiotropic genetic control, at least to a certain degree, (iv) the same result was obtained for Cd and Zn accumulation.