The interaction of the vanadyl(IV) cation with phytic acid

The interactions of VO²⁺ with phytate to form both soluble and insoluble complexes, have been studied by electronic absorption spectroscopy. A soluble 1∶1 VO²⁺: phytate complex is formed at pH <1. At higher pH-values insoluble complexes are produced. Two different solid complexes, obtained respectively at pH=2 and 4, were isolated and characterized. The maximal bonding ratio of VO²⁺: phytate was found to be 4, on the basis of a pH binding profile.     

Size dependent metal concentrations in two marine gastropod species

The effect of size on the accumulation of Cd, Cr, Cu, Mn, Ni, Fe and Zn in the muscle and viscera of the gastropodsMonodonta turbinata andCerithium vulgatum was investigated. The concentration of the essential metals Cr, Mn and Ni and the non-essential metal Cd decreased with increasing size in both of the species and tissues. The concentration of the essential metals Cu, Fe and Zn, showed a less constant relation with size.     

Soil factors affecting patchiness in community composition of heavy metal-contaminated areas of Western Europe

The vegetation at various sites within two separate areas (Mechernich and Aachen) of the Eifel Mountains, Germany/Belgium, both characterized by elevated concentrations of heavy metals in their soils, was surveyed in order to investigate the relationships between soil chemical attributes and floristic composition. In both areas, the typical heavy metal communities can form distinct zones, clearly separated from the surrounding heavy metal-sensitive vegetation. However, an intergrading of heavy metal-tolerant and-sensitive vegetation types is not uncommon and such overlaps can occupy large areas. In Mechernich, soil toxicity is primarily determined by the effects of lead, which is best expressed in terms of the Pb/Ca ratio rather than the absolute levels of this metal in the soil. Soils of heavy metal-sensitive vegetation types have a low Pb/Ca ratio, whereas it is considerably higher in areas supporting heavy metal vegetation. Zinc appears to exert little influence on the floristic composition of the investigated vegetation types. In Aachen, zinc is the predominant heavy metal determining vegetation development. Absolute zinc levels of soils do not accurately reflect zinc toxicity. Analogous to the role of the Pb/Ca ratio in the Mechernich area, the Zn/Ca ratio not only separates heavy metal-sensitive and highly tolerant vegetation units, but also gives a good indication of the gradient operating between the two vegetation types. Lead is probably only of local importance in influencing species composition.     

几种氨基酸─铜（Ⅱ）配合物的超氧化物歧化酶活性

用四氮唑蓝光化学还原法对所合成的ＫＣｕ（ＩＤＡ）（Ｓｅｒ）·２Ｈ２Ｏ、ＫＣｕ（ＩＤＡ）（Ａｌａ）·Ｈ２Ｏ、Ｃｕ（ＩＤＡ）（ｅｎ）、ＫＣｕ（ＩＤＡ）（Ｇｌｙ）·Ｈ２Ｏ和Ｃｕ（ＩＤＡ）·２Ｈ２Ｏ（ＩＤＡ＝Ｎ（羧基甲基）－甘氨酸,Ｓｅｒ＝丝氨酸,Ａｌａ＝丙氨酸,ｅｎ＝乙二胺,Ｇｌｙ＝甘氨酸）等５种氨基酸─铜（Ⅱ）配合物进行了活性测定,发现它们均具有天然超氧化物歧化酶活性,其活性依次为０．３４、０．４５、０．５０、０．５４、０．７２Ｃｕμｍｏｌ·Ｌ－１。     

Construction and evaluation of a metal ion biosensor

Escherichia coli, genetically engineered with a mercury(II)-sensitive promoter and the lux genes from Vibrio fischeri, were used as microbial bioluminescent sensors for the detection of mercury. Evaluation of this genetic construction was carried out by determining the effects of various parameters on cell suspensions maintained at constant conditions in a small 100-mL vessel. The strongest light intensities and quickest induction times occurred with cells in the midexponential growth phase maintained at 28 degrees C, concentrated to 1 x 10(9) cells/mL, mixed at very fast speeds, and aerated at 2 vvm (volume of air per volume of culture per minute) during light measurement in the small vessel. The cells were sensitive to the mercuric ion in the range of 20 nM to 4 muM (4 to 800 ppb), and the total response time was on the order of 1 hour, depending on the above parameters. The cells exhibited great specificity for mercury. The cells had almost equal specificity for organic and inorganic forms of the mercuric ion and responded more weakly to the mercurous ion. A simple, inexpensive, durable miniature probe (3 mL) was constructed and operated using the optimum parameters found in the small vessel as a guide. The range of sensitivity to the mercuric ion detected in the probe was 10 nM to 4 muM when aeration was provided. (c) 1993 John Wiley & Sons, Inc.     

Metal resistance in Acinetobacter and its relation to β-lactamase production

Thirty nine clinical isolates of Acinetobacter belonging to six species were tested for resistance to 20 metal ions and their ability to produce -lactamase. Fifty two percent of the strains produced -lactamase. -Lactamase producers and non-producers were almost equally distributed in the different species. A. baumannii was the predominant biotype and was found to be most resistant to metals. Resistance to mercury was prevalent in -lactamase-producing A. baumannii only. Silver resistant strains of A. baumannii produced -lactamase. Sensitivity and resistance to copper and cadium was equally distributed between -lactamase producers and non-producers. -Lactamase-producer and -non-producer strains were uniformly sensitive to cadmium except Acinetobacter genospecies 1.     

Ter-Seq: A high-throughput method to stabilize transient ternary complexes and measure associated kinetics

Regulation of biological processes by proteins often involves the formation of transient, multimeric complexes whose characterization is mechanistically important but challenging. The bacterial toxin CcdB binds and poisons DNA Gyrase. The corresponding antitoxin CcdA extracts CcdB from its complex with Gyrase through the formation of a transient ternary complex, thus rejuvenating Gyrase. We describe a high throughput methodology called Ter-Seq to stabilize probable ternary complexes and measure associated kinetics using the CcdA-CcdB-GyrA14 ternary complex as a model system. The method involves screening a yeast surface display (YSD) saturation mutagenesis library of one partner (CcdB) for mutants that show enhanced ternary complex formation. We also isolated CcdB mutants that were either resistant or sensitive to rejuvenation, and used surface plasmon resonance (SPR) with purified proteins to validate the kinetics measured using the surface display. Positions, where CcdB mutations lead to slower rejuvenation rates, are largely involved in CcdA-binding, though there were several notable exceptions suggesting allostery. Mutations at these positions reduce the affinity towards CcdA, thereby slowing down the rejuvenation process. Mutations at GyrA14-interacting positions significantly enhanced rejuvenation rates, either due to reduced affinity or complete loss of CcdB binding to GyrA14. We examined the effect of different parameters (CcdA affinity, GyrA14 affinity, surface accessibilities, evolutionary conservation) on the rate of rejuvenation. Finally, we further validated the Ter-Seq results by monitoring the kinetics of ternary complex formation for individual CcdB mutants in solution by fluorescence resonance energy transfer (FRET) studies.     

Growth of cells in a new defined protein-free medium

The development of a new stable synthetic serum replacement (SSR) is described, which allows the cultivation of mammalian cells in a defined, protein-free medium containing only dialyzable components. With a low concentration of insulin (RPMI-SR2 medium), growth rates of the transformed cell lines L929, HELA S3, and the hybridoma 1E6 were comparable to growth rates obtained with a serum-containing medium. The same medium also supported long-term cultivation of non-dividing mouse macrophages. The main principle of SSR is a metal ion buffer containing a balanced mixture of iron and trace metals. Stability against precipitation of important metals is achieved by the combined use of EDTA and citric acid as chelating agents. Efficient iron supply is mediated through the inclusion of the compound Aurintricarboxylic acid as a synthetic replacement for transferrin. SSR also contains a growth-promoting surfactant, Pluronic F68. Thus SSR provides a general foundation for growth and differentiation normally provided by serum.Limitations of other serum-free medium designs are discussed here: 1) the inability of transferrin to chelate all metals in the medium; and 2) the use of inorganic iron salts or iron citrate as an iron supplement leads to rapid precipitation of iron hydroxide in the medium. Both these problems are solved in the design of SSR.     

Silicon and Nitric Oxide-Mediated Regulation of Growth Attributes,Metabolites and Antioxidant Defense System of Radish (<i>Raphanus sativus</i> L.) under Arsenic Stress

Arsenic (As) contaminated food chains have emerged as a serious public concern for humans and animals and are known to affect the cultivation of edible crops throughout the world. Therefore, the present study was designed to investigate the individual as well as the combined effects of exogenous silicon (Si) and sodium nitroprusside (SNP), a nitric oxide (NO) donor, on plant growth, metabolites, and antioxidant defense systems of radish (Raphanus sativus L.) plants under three different concentrations of As stress, i.e., 0.3, 0.5, and 0.7 mM in a pot experiment. The results showed that As stress reduced the growth parameters of radish plants by increasing the level of oxidative stress markers, i.e., malondialdehyde and hydrogen peroxide. However, foliar application of Si (2 mM) and pretreatment with SNP (100 µM) alone as well as in combination with Si improved the plant growth parameters, i.e., root length, fresh and dry weight of plants under As stress. Furthermore, As stress also reduced protein, and metabolites contents (flavonoids, phenolic and anthocyanin). Activities of antioxidative enzymes such as catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (POD), and polyphenol oxidase (PPO), as well as the content of non-enzymatic antioxidants (glutathione and ascorbic acid) decreased under As stress. In most of the parameters in radish, As III concentration showed maximum reduction, as compared to As I and II concentrations. However, the individual and combined application of Si and NO significantly alleviated the As-mediated oxidative stress in radish plants by increasing the protein, and metabolites content. Enhancement in the activities of CAT, APX, POD and PPO enzymes were recorded. Contents of glutathione and ascorbic acid were also enhanced in response to co-application of Si and NO under As stress. Results obtained were more pronounced when Si and NO were applied in combination under As stress, as compared to their individual application. In short, the current study highlights that Si and NO synergistically regulate plant growth through lowering the As-mediated oxidative stress by upregulating the metabolites content, activity of antioxidative enzymes and non-enzymatic antioxidants in radish plants.

     

Subcellular Distribution and Chemical Forms of Cadmium in the Medicine Food Homology Plant <i>Platycodon grandiflorum</i> (Jacq.) A.DC.

Although Platycodon grandiflorum (Jacq.) A.DC. is a renowned medicine food homology plant, reports of excessive cadmium (Cd) levels are common, which affects its safety for clinical use and food consumption. To enable its Cd levels to be regulated or reduced, it is necessary to first elucidate the mechanism of Cd uptake and accumulation in the plant, in addition to its detoxification mechanisms. This present study used inductively couple plasma-mass-spectrometry to analyze the subcellular distribution and chemical forms of Cd in different tissues of P. grandiflorum. The experimental results showed that Cd was mainly accumulated in the roots [predominantly in the cell wall (50.96%–61.42%)], and it was found primarily in hypomobile and hypotoxic forms. The proportion of Cd in the soluble fraction increased after Cd exposure, and the proportion of insoluble phosphate Cd and oxalate Cd increased in roots and leaves, with a higher increase in oxalate Cd. Therefore, it is likely that root retention mechanisms, cell wall deposition, vacuole sequestration, and the formation of low mobility and low toxicity forms are tolerance strategies for Cd detoxification used by P. grandiflorum. The results of this study provide a theoretical grounding for the study of Cd accumulation and detoxification mechanisms in P. grandiflorum, and they can be used as a reference for developing Cd limits and standards for other medicine food homology plants.