Chelating Agents - The Natural Recovery Plan

Chelation Natural Miracle For Protecting Your Heart

Chelation therapy has been conclusively shown to be up to 82 Percent Effective at dissolving the plaque that blocks arteries! In the ebook Chelation Natural Miracle For Protecting Your Heart you'll discover: The frustrating reason many doctors are ignoring Edta chelationor even openly rejecting it. The deadly heart surgeries even the American Heart Association admits are unnecessary. The hidden signs and symptoms of heart attacks and strokes? Are you in danger right now?. The average number of years stripped away by heart and vessel disease. Can you get them back?. The newest set of risk factors for heart disease (they'll likely surprise you!). Shady government practices that protect Big Pharma and keep Edta chelation out of the public eye. How the Roman Empire could have been savedif only they'd known about Edta chelation. Why Edta chelation is guaranteed to be safeeven in extremely high doses. (It puts aspirin to shame!). The shocking truth about plaque in young childrenand how to keep your little ones safer. Why dentists, artists and welders need Edta chelationand whether your workplace is dangerous too. The differences between IV and oral chelationand which kind of Edta is right for you. Other forms of chelationand how these little-known treatments can dramatically boost your health.

Chelation Natural Miracle For Protecting Your Heart Summary

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Specific Metal Chelating Agents Siderophores

Mechanisms such as reductive assimilation and protonation are also used by some organisms with the aim of solubilizing iron from their environments (Guerinot 1994 Kosman 2003). Although plants (grasses) produce these compounds (phyto-siderophores), the chemical structures and chelation mechanisms differ from those of fungal and bacterial origin (Sugiura and Nomoto 1984 Kraemer et al. 2006 Crowley 2006). Siderophores are synthesized by cells as metal-free ligands (desferrisidero-phores), which are excreted into the extracellular environment where they solubi-lize the iron by chelation and return to the cell as ferrisiderophores, releasing the iron through different mechanisms (Hider 1984 Guerinot 1994 Neilands 1995 Renshaw et al. 2002 Kraemer 2004). At least four different mechanisms have been proposed for the transport of ferrisiderophores to the cell, mostly based on the recognition of ferric complexes by specific transport systems present in the cell membrane. Once inside the cell,...

Nonspecific Metal Chelating Agents Low Molecular Weight Organic Acids

Low molecular weight (LMW) organic acids, along with siderophores, are among the main mediators of the biological weathering of soils caused by living organisms, leading to the dissolution of a variety of minerals through a double effect of metal cation chelation and anion displacement by protonation (Landeweert et al. 2001 Gadd 2007 van Scholl et al. 2008). In soils, organic acids come mainly from plants that release them into the rhizosphere by exudation from their roots, as well as from fungi and bacteria, and chemically they are carboxylic acids, with one or more functional groups per molecule (e.g., formic, malic, oxalic, citric, succinic, etc.). Those acids that present more than one carboxylic group (di- or tricarboxylic) are important in the formation of complexes with metal ions and can be considered as metal-chelating agents. Under the normally existing pH conditions in biological systems, these acids are found in the form of carboxylate anions (e.g., oxalate, citrate,...

Biotechnological Potential of ECM Fungi Producing Metal Chelating Agents

The biotechnological potential of ECM fungi producing metal-chelating agents is related to the isolated chelators with specific aims, or to the use of the fungi in the presence or absence of symbiotic association. Due to their extremely efficient metal-chelating properties, for many years the main application of siderophores has been in chelation therapy to treat Fe and Al overload in humans its possible use in the decorporation of actinides is also being investigated. The main siderophore used for this purpose is desferrioxamine B, a hydroxamate obtained from Strepto-myces pilosus (Messenger and Ratledge 1985 Renshaw et al. 2002 Ansoborlo The revegetation of metal-contaminated soils is another important application of plants mycorrhized with ECM fungi producing a wide range of chelators siderophores, LMW organic acids, MTs, PC, and GSH. Given that these chelators contribute to the detoxification of metals through intracellular or extracellular mechanisms, the fungal species that...

Dissolution Of Soil Native Iron By Chelating Agents

When the Fe-chelate releases Fe to the plant, the chelating agent may dissolve native Fe (Figure 5-1), which can be then transported to the plant (Chen and Barak, 1982 Lindsay, 1995 Lucena, 2003). However, the importance of this dissolution process in plant Fe nutrition is not well known. Schwertmann (1991) reviewed the knowledge on the processes of dissolution of Fe oxides, indicating that most of the studies concerning chelating agents have been done for the estimation of the plant-available Fe. The chelating agent may dissolve native Fe present in the solid phases. This is a kinetically controlled process that depends on the chelating agent (Stone, 1977), the nature of the solid phase (Schwertmann 1991 Perez-Sanz and Lucena 1995 Nowack and Sigg, 1997) and the soil conditions. The rate of dissolution may be the limiting factor for the whole process. It has been hypothesized that kinetics, rather than equilibrium, probably controls the speciation of low stability complexes (such as...

Other Metal Chelating Agents Thiol Peptides

MTs are peptides of low molecular weight (6-7 kDa), rich in cysteine (Cys), highly ubiquitous - given that they have been identified in animals, plants, fungi, and some bacteria - with the capacity to chelate metals through the thiol (-SH) groups. Some MTs can contain up to 60 amino acids, of which fewer than half correspond to Cys they do not exhibit aromatic amino acids or histidine. MTs can form clusters with a large amount of divalent or monovalent metal ions through the domains rich in Cys (Robinson et al. 1993). The biosynthesis of MTs is regulated at transcriptional level by a variety of factors, among them some metals Cd, Zn, Hg, Cu, Au, Ag, Co, Ni, and Bi (Kagi and Shaffer 1988) and of these Cu, Zn, Cd, Hg, Bi, Ag, Au, as well as Pb and Pt can be indeed chelated (Koagi 1991). However, the preference for one or the other metal, both in the regulation of biosynthesis and in chelation, depends exclusively on the organism (Robinson et al. 1993 Hall 2002). MTs were described in...

Chelation at Cytoplasm and Vacuole Level

Chelation in the cytoplasm is an intracellular buffer system to control PTE toxicity through reduction of the concentration of cytotoxic-free PTE ions. In this system, metallothioneins (MT), metal-binding polypeptides, and or MT-like proteins may be involved. In contrast to ectomycorrhizal fungi, the participation of these compounds in metal detoxification has not been confirmed in AMF 69,70 . However, evidence suggesting the presence of Cd-binding thiols in AMF as well as high concentrations of N and S in mycorrhizal roots exposed to Cd have been reported 71,72 . Galli et al. 72 studied the effect of Cu on the uptake, amount, and composition of Cu-binding peptides (Cu-BPs) of mycorrhizal maize plants inoculated with Glomus intraradices. They observed increased concentrations of the thiols cysteine, y-glutamylcysteine, and glutathione up to an external Cu supply of 9 g g-1. However, the amount of thiols in Cu-BPs was not increased by mycorrhizal colonization in Cu-treated plants and...

Isolation of Clathrin Coated Vesicles

Plant clathrin-coated vesicles (CCVs) were isolated from cucumber and zucchini hypocotyls (Depta et al., 1991 Holstein et al., 1994). CCV components were protected against proteolysis using homogenization media composed of 0.1 M MES (pH 6.4), 1 mM EGTA, 3 mM EDTA, 0.5 mM MgCl2, a mixture of proteinase inhibitors and 2 (w v) fatty-acid-free BSA (Holstein et al., 1994). The crude CCV fraction (40 000-120 000 g pellet) was further purified by cen-trifugation in Ficoll sucrose according to Campbell et al., (1983) and then by isopycnic centrifugation in a sucrose density gradient using a vertical rotor (160 000 g, 2.5 h, Depta et al., 1991). CCV-enriched fractions (collected at 40-45 sucrose) were removed, pooled and pelleted. CCV fractions were stored at - 80 C for further use. Immunoblotting was performed using monoclonal antibodies against mammalian adaptins and clathrin. Confirmation of the presence of a P-type adaptin in plants was provided by dot and Southern blotting experiments...

Isolation of Plasma Membrane Lipid Rafts

Recently, lipid raft plasma membrane domains were identified in plants based on their insolubility with the detergent Triton X-100 (Berczi and Horvath, 2003 Mongrand et al., 2004 Borner et al., 2005). First results obtained using thin-layer chromatography revealed that both quantitative and qualitative differences exist between the lipid composition of plant plasma membranes isolated from etiolated bean hypocotyls and green Arabidopsis leaves (Berci and Horvath, 2003). Later, protocols for the preparation of Triton X-100 detergent-resistant membranes (DRMs) from Arabidopsis callus were developed by Borner et al., (2005). Further, a proteomics approach using two-dimensional gel electrophoresis and liquid chromatography-tandem mass spectrometry revealed that the DRMs were highly enriched in specific proteins. Among them, eight glycosylphosphatidylinositol (GPI)-anchored proteins, several plasma membrane (PM) ATPases, multidrug resistance proteins and proteins of the stomatin prohibitin...

Profile Development Influence of Pedogenesis

Weathering and leaching are not the only processes that cause the development of horizons. Plants draw their moisture and nutrients from a relatively large volume of soil but, assuming they are not harvested, will return their inorganic constituents to the surface through leaf fall or generally to the upper layers through root death. The fresh organic material is food for many organisms, which, in turn, live on each other. Thus, organic material changes until the end product, a black or brown organic material with a lignin-like structure, called humus which enriches the surface layers. Humus is a store of trace metals through adsorption, since it carries a negative charge like the clays, or through complexation (chelation). Metals may be released as humus oxidises (mineralises) or by desorption or decomplexation (Shuman, 1988 Livens, 1991).

Root Organic Exudates Trace Element Mobilization in the Rhizosphere and Their Bioavailability

Plants growing under conditions in which Fe and or Zn are deficient can actively increase the availability of these metals, releasing specific organic compounds. Different strategies have been proposed by Marschner et al. 39 and Roemheld 40 . Among them, strategy I is active in dicotyledonous and monocotyledonous species with the exception of graminaceous species. This strategy is based on a three-component system constituting a plasma membrane-bound inducible reductase an enhanced excretion of protons and the release of reducing and chelating agents 26 . Strategy II (active in graminaceous plants) is based on the release of phytosiderophores in the rhizosphere and specific uptake system on the root surface. The exudation of organic acids may also be important for increasing nutrient availability. Moghimi et al. 53 were able to isolate a-ketogluconate from the rhizosphere of wheat roots in quantities that could solubilize considerable amounts of phosphate from hydroaxyapatite. This...

Measurement of the Bioavailable Fraction

The strong association of copper and zinc with soil humus has stimulated a wide interest in solutions of chelating agents (eg, Viro, 1955 Tills and Alloway, 1983). These are supposed to act by mimicking the activities of the plant roots in decomplex-ing metals from the organic matter. However, the quantities of trace metals which they liberate are far higher than those mobilised by the roots. In England and Wales the National Agricultural Advisory Service presently uses disodium EDTA (ethylene-diamine-tetraacetic acid) for copper and soil concentrations in the range 0-1.6 mg Cu L_1 indicate the likelihood of deficiencies while concentrations between 1.7 and 2.4 mg L 1 suggest the possibility of crop deficiencies. In the USA a mixed reagent containing (0.005 m) DTPA (diethylenetriaminepentaacetic acid) with (0.1 m) TEA (triethanolamine) and 0.01 m calcium chloride (CaCl2) at pH 7.3 has been widely adopted (Lindsay and Norvell, 1978). Copper deficiencies are associated with soil levels

Synthetic iron chelates

The prevention and the cure of Fe chlorosis in fruit trees have been traditionally approached through the application of synthetic Fe chelates (Lucena, 2003). Several Fe chelators are available, those mainly used being EDTA (ethylenediaminetetraacetic acid) and DTPA (diethylenetriaminepenta-acetic acid) characterized by a low stability constant and suitable for foliar applications, and EDDHA acid , EDDHMA acid and EDDHSA acid , with higher stability constants (Lucena et al., 1996) and suitable for soil supply. Soil application of Fe chelates aims at enhancing Fe availability for uptake at the root level and represents an efficient prevention method, provided no

MARK Interacts with MIK a GCKlike Kinase

GST pull-down experiments performed between MARK-KD and MIK. (A) The complete DH5-MIK sequence, as well as different deletions of DH5-MIK (a-c), were fused to GST and immobilized on to glutathion-S-Sepharose and were incubated with recombinant His-tagged MARK-KD, using GST as a negative control, in binding buffer (Hepes pH 7.9 20 mM, glycerol 20 , EDTA 0.2 mM, NaCl 150 mM, NP40 0.5 , PMSF 0.1 mM, DTT 0.5 mM). After extensive washing with the same buffer, proteins were eluted with Laemmli buffer, separated by SDS-PAGE and transferred to nitrocellulose. Immunodetection was performed with an anti-MARK polyclonal antibody. (B) Immobilized GST and GST fused MARK-KD, as well as three different MARK-KD mutants (A-C) were incubated with His-tagged DH5-MIK as described in (A). Immunodetection was performed with an anti-DH5-MIK polyclonal antibody. Fig. 7.4. GST pull-down experiments performed between MARK-KD and MIK. (A) The complete DH5-MIK sequence, as well as different deletions...

DNA extraction and electrophoresis

DNA extraction was based on the method of Young and Gallie (2000), which was modified as follows. Thirty axes from seeds subjected to accelerated ageing for different periods of time were homogenized to a fine powder with a mortar and pestle under liquid nitrogen. DNA was subsequently extracted by grinding the powder in 200 ll of an extraction buffer composed of 10 mM tris- (tris-HCl) at pH 8.0, 10 mM NaCl, 10 mM ethylene-diaminetetraacetic acid (EDTA) and 1 (w v) sodium dodecyl sulphate (SDS). Following this, 50 l (1.0 mg ml) protease K was added to the homogenate and incubated at 37 C for 30 min. After incubation, 200 ll 2 (w v) cetyltrimethylam-monium bromide (CTAB), 400 ll chloroform isopentanol (24 1) and 400 ll trisphenol were added to the mixture to remove proteins. The mixture was centrifuged at 12,000g for 5 min and then 100 Ul isopropanol was added to the supernatant. The supernatant was centrifuged at 12,000g for 5 min once again, and the resulting DNA was washed in 70 (v...

Ironfertilization increases fruit quality

Factors affecting fruit quality other than fruit size have been mainly studied in Citrus spp. The first trials with Fe-EDTA in Florida already indicated that Fe fertilization in Fe-deficient Citrus trees improved fruit quality, increasing soluble solids and volume of juice per fruit, slightly decreasing titratable acid in the juice and improving fruit color (Sites et al., 1953). Increases in yields of Fe-deficient Citrus aurantifolia after soil and foliar Fe fertilization were associated with increases not only in fruit weight (30 ) but also in juice contents (10 ), and also to decreases in total acidity (10 ), total soluble solids (25 ) and ascorbic acid concentrations (10 ), probably because of the dilution effect caused by a larger amount of juice per fruit (El-Kassas, 1984). Foliar Fe treatments repeated 10 times during the year (from August to February) increased the quality of March-harvested fruits in Citrus sp. through increases in fruit size and juice content and decreases in...

Sorption Of Ironchelates On Soil Surfaces

Since adsorption-desorption reactions tend to be faster than precipitation-dissolution processes, adsorption at solid interfaces can be a dominant factor in regulating micronutrient concentrations in solution (Harter, 1991 Stone, 1977). Adsorption or fixation of chelating agents in soils was recognized in early investigations of the agricultural uses of synthetic chelating agents (Wallace and Lunt, 1956 Hill-Cottingham and Lloyd-Jones 1957 Aboulroos et al., 1983 Norvell, 1991). The effectiveness of Fe-chelates as Fe sources and carriers in soil can be severely limited by the adsorption of Fe-chelates or chelating agents in the solid phase (Sanchez-Andreu et al., 1991). The factors affecting adsorption include the type of chelating agent, the metal ion, time, pH, salt concentrations and soil texture (Aboulroos et al., 1983). Wallace et al. (1955) added various chelates, including Fe(III)-EDDHA, to soils, and found that after 4 days chelating agent losses in a calcareous loam soil...

Colonisation and succession

Bryophytes and lichens are effective colonisers during early stages of succession on dry land. They were traditionally believed to have an important influence on rock weathering, but this point is currently somewhat controversial. Both groups are likely to be beneficial in terms of increasing the availability of nitrogen in immature soils (Chapter 7). The role of lichens in colonising rock surfaces has been discussed by Syers & Iskandar (1973), Ugolini & Edmonds (1983), and by Topham (1977) who noted that the adaptations facilitating colonisation include tolerance of desiccation and extreme temperatures, longevity and low growth rates. Physical weathering is accelerated by rhizine penetration in foliose species, and by expansion and contraction of appressed, partially endolithic, crustose thalli in response to changes in water content. Lichens may induce chemical weathering by liberating oxalic acid, various lichen acids and carbonic acid formed when carbon dioxide released by...

Evidence from Gene Cloning

Sequences of cloned genes are available for bioinformatic analysis and alignment to construct phylogenetic trees, to search for variants in coding sequences, to search differences for those promoter sequences which may be related to differential gene expression. The alleles for ZNT1 cloned from the two accessions of T. caerulescens Prayon and La Calamine differ by 30 amino acids at the N-terminus and 5 amino acids inside the coding sequence (Assuncao et al. 2001). In a phylogenetic tree, ZIP transporters from angiosperms were compared, including ZNT and IRT genes (Plaza et al. 2007). Allelic variants among ecotypes of T. caerulescens are evidenced, pointing for a possible role in metal tolerance. To assess the importance of single amino acid residues, Song et al. (2004) compared the gene AtPcrs1, involved in tolerance to Cd, to other similar sequences present in A. thaliana and Oryza sativa L Modified gene sequences were checked for their capability in conferring Cd tolerance in...

Iron homeostasis and translocation as affected by other metals

The intracellular level of Fe and other heavy metals are by all means strictly regulated, and different substances are involved in the process. Nicotianamine (NA), a non-proteogenic amino acid ubiquitous in higher plants, seems to be the principal chelator of Fe within the cell when Fe is not bound to target molecules such as heme or stored as phytoferritin (Hell and Stephan, 2003). Nicotianamine may function in keeping Fe soluble and available as well as preventing Fenton reactions, which lead to oxygen radical formation when free Fe2+ ions are present (von Wiren et al., 1999). Organic acids and amino acids are also available chelating agents for Fe, although the stability constants of those complexes are high enough only for Fe3+ (see Table 6-1 for citrate). The synthesis of potential chelating agents in the cytoplasm may raise the question of competition between metals for organic ligands, especially under conditions of hyperaccumulation. Although the basic factors determining the...

Incorporation Of Metals In Bioactive Molecules In The Process Of Evolution

Once it gathers these different metals, how does the cell know which metal to put into which enzyme-active site A traditional view in the field of bioinorganic chemistry has been that metal selectivity is due to very sophisticated chelating properties of the individual apo-proteins. In this scenario, apo-proteins are thought to poise the exact orientation of these side chains to match the precise ionic radius and electronic preference of the functional metal ions, for example, Zn2+, and to discriminate against all others, such as Cu2+ or Fe2+ ions. In some of these cases, very little difference is present in ionic radii. The proteins are thus viewed as highly specific chelating agents with finely tuned kinetic and thermodynamic properties that have been selected through evolution to bind only one type of transition metal ion. In this model, each apo-protein as it is produced in the cell simply selects a metal ion from the cytoplasm. In general, however, the field has moved to the...

Cadmium and Copper Uptake and Homeostasis

To avoid Cu deficiency, plants have high-affinity Cu transporters belonging to the COPT family to ensure Cu+-uptake under low Cu availability, after reduction of Cu2+ by ferric reductase (FRO). The uptake systems when plants are exposed to excess Cu have not yet been revealed. These could be COPT3-5, which are not affected by Cu levels, unlike COPT1 and COPT2 that are down regulated by excess Cu. Otherwise, Cu2+, which is the most abundant form present in soil, could be taken up by ZIP (zinc-regulated transporter iron-regulated transporter-like or ZRT IRT-like) transporters (Burkhead et al. 2009 Palmer and Guerinot 2009). However, these bivalent cation transporters are also important uptake systems for non-essential elements such as Cd. This is due to the chemical similarity of Cd2+ ions with the ions of these essential elements (Clemens 2006 Perfus-Barbeoch et al. 2002 Verbruggen et al. 2009). Therefore, when growing on soils contaminated with excess metals, unspecific metal uptake...

Complexing properties and reducing capacity

To the heterogeneity of humic substances concerning molecular weight, content of functional groups, variety of bonding sites and changes in conformation of these macromolecules with pH and salt concentration, it is difficult to reach an unequivocal state of knowledge (Chen and Stevenson, 1986). Attempts have been made to determine the apparent stability constants (Kapp) for Fe3+ with two hydrophobic fractions of dissolved organic matter obtained from a manure compost, after sorption onto XAD-8 resin (Chen et al., 2004). The Kapp values at pH 5.0 and an ionic strength of 0.1 M were 7.91 for the fraction desorbed with NaOH and 6.76 for that desorbed with methanol. Garcia-Mina et al. (2004) investigated the stability of different metal-humic complexes (NaOH extracted) in the pH range 6-9 and ionic strength of 3 mM, and found maximal Kapp values (4.11) at pH 8.0. These values are somewhat lower than the maximal stability constant values determined for complexes between Fe and synthetic...

Nutritional Antioxidants And Polyphenolic Flavonoids

Scavenging of free radicals, chelation of transition metal ions, or protection of the intrinsic antioxidants in the LDL particle (vitamin E and carotenoids) from oxidation. as well as of superoxide anion.2526 Some act also as antioxidants due to their potent chelation capacity of transition metal ions.2627 Furthermore, flavonoids can preserve serum paraoxonase 1 (PON1) activity probably as a result of the reduction in the level of oxidized lipids.28,29 Flavonoids are also quite suitable for protecting cell membranes from free-radical-induced oxidation, since they are both lipophilic and hydrophilic and thus are able to scavenge free radicals, which are generated within the cells, as well as free radicals that attack the cell membrane from the outside. Indeed, flavonoids were shown to reduce macrophage oxidative stress and cellmediated oxidation of LDL.30

Role Of Humic Substances As Natural Ironchelates

Due to their ability to maintain Fe in solution, soluble Fe-humate complexes can act as natural Fe-chelates available for plants. Because of their complexing ability, it is generally accepted that water-soluble humic molecules can mobilise Fe from soil particles to the root surface. The quantitative aspects of this process have not yet been elucidated. It is reasonable to think that the importance of the Fe-humate complexes depends on the humic substances Fe ratio. As proposed by Linsday and Schwab (1982) for the movement of Fe-EDTA chelate from the solid phase of the soil to the root, the following scenario can be hypothesised in the case of soluble humic molecules at a low humic substances Fe ratio, the molecules will tend to mobilise Fe from the solid phases to form stable complexes. If the amount of Fe is not sufficient to form humic macromolecules of lower solubility (see previous section) the soluble complex will move by diffusion toward the roots. Evidence supporting this view...

Microbial Siderophores In The Plant Rhizosphere

Abstract Siderophores are iron chelating agents that are produced by almost all microorganisms in response to iron deficiency. Due to the requirement of iron for cell growth and metabolism, siderophore mediated acquisition of iron plays a central role in determining the ability of different microorganisms to colonize plant roots and contributes to microbial interactions in the plant rhizosphere. There are now approximately 500 known siderophores, some of which are widely used by a variety of microorganisms, whereas others are used only by the same microbial species and strains that produce them. Siderophores also have been examined for their potential importance in plant iron nutrition and for their ability to mobilize heavy metals. There has been considerable debate over their relative importance for plant iron nutrition that has centered around their ability to release iron by means of chelate reductases that function in Strategy I plants and to exchange iron with phytosiderophores...

Mobilization Of Iron By Siderophores 21 Iron availability in the plant rhizosphere

The rates of iron oxide dissolution vary with respect to their crystallinity, ranging from amorphous iron oxides that are relatively easy to dissolve to goethite and hematite, which have very slow dissolution rates. Iron oxides and clay silicates are often associated with humic and fulvic acids, organic acids, and polysaccharides in clay-organic matter complexes that can further affect their dissolution rates and surface chemistry. To date, there are only a few model systems that have been studied, in which the kinetics of iron dissolution from different solid phases has been determined empirically for a few representative siderophore and phytosiderophores types and with a few representative synthetic or natural iron oxides. As compared to chelation with soluble iron which is instantaneous, the surface dissolution kinetics of iron oxides is relatively slow and may take hours to days for all of the siderophore to become complexed with iron. The rates of dissolution will depend on the...

Cd Uptake from Soil to Roots

Most studies have shown that the main site of Cd accumulation in roots is the apoplast, particularly cell walls. Using energy-dispersive X-ray microanalysis, Cd was determined in cortex parenchyma cells, endodermis, parenchyma cells of the central cylinder, and xylem vessels in T. caerulescens (Wojcik et al. 2005). After treatment with 20 ppm Cd, about 13 of the total Cd in T. caerulescens roots was associated with organic acids (Boominathan and Doran 2003). Nedelkoska and Doran (2000) have found retention of almost the whole pool of Cd taken up in the fraction of cell wall of Thlaspi roots, and then diffused into the symplast after 7-10 days of exposure to 200 p.M Cd. The authors also suggested that such a delay in Cd transport through membranes inside cells is an important defense mechanism against Cd toxicity, enabling simultaneous activation of intracellular detoxification mechanisms of Cd such as chelation and antioxidative defense.

Antioxidative Potency Of Fractions Isolated From Pomegranate Juice

Several fractions were isolated from pomegranate juice, including gallic acid, ellagic acid, tannins, total PJ anthocyanins, and specific anthocyanins such as cyanidin-3-0-P-glucopyranoside, cyanidin-3,5-di-0-P-glucopyranoside, delphinidin-3-0-P-glucopy-ranoside, and pelargonidin-3-0-P-glucopyranoside. The total anthocyanin and tannin fractions exhibited a dose-dependent antioxidative effect against copper ion-induced LDL oxidation. In the AAPH-induced LDL oxidation, both fractions exhibited weaker antioxidative properties in comparison to the copper ion-induced LDL oxidation. These results suggest that the anthocyanins and tannins also possess transition metal ion chelation properties in addition to their free-radical scavenging capabilities. The tannin fraction was more potent than the anthocyanin fraction in inhibiting LDL oxidation, and the IC50 of the tannins was half that of the anthocyanins. Both PJ ellagic and gallic acids and the anthocyanins...

Reductionoxidation Reactions Of Metals And Metalloids

Masschelyn and Patrick (1994) have summarized the critical redox potentials for the transformation of some metal contaminants in soil environments. There has been little information on how changes in soil redox potential in the rhizo-sphere could affect the transformation of metal and metalloid contaminants. The generation of biomolecules through root exudation and microbial metabolism in the rhizosphere influences the redox potential. From a thermodynamic point of view, complexation of ligands with metals both on solid and solute phases has a dramatic effect on the redox potentials (Stumm and Morgan, 1996). For exemplification, Fe(II) and Fe(III) are used to illustrate the consequences of complexation on the redox potentials because (1) more data are available with this redox pair than with others, and (2) the transformations of Fe are especially important in the redox cycling of electrons in natural environments. The Fe(III) Fe(II) redox couple can be adjusted with appropriate...

Frankiaactinorhizal root nodule symbiosis

When following the uptake of 55Fe, Boyer et al. (1999) observed that Frankia strain 52065 showed greater preference for ferric loaded desferal or frankobactin than for citrate, EDTA, or pseudobactin. Since desferal is a derivative of ferrioxamine B, the main siderophore of Streptomyces pilosus, ferrioxamine B was also tested and the rate of 55Fe uptake with both of these siderophores was comparable. The uptake of frankobactin by Frankia is by an energy-requiring mechanism (Boyer and Aronson, 1994).

Plant Mechanisms to Cope with Cadmium

Plants have also developed intracellular strategies against Cd toxicity such as transport to the major storage organs or tissues, chelation and subcellular com-partmentalization and the efflux from the plant (Benavides et al. 2005 Verbruggen et al. 2009 Sharma and Dietz 2009). As described previously, Cd enters first by the roots through the cortical tissue. Roots accumulate Cd during its exposure and part of the metal is then translocated to leaves (Ogawa et al. 2009). Cd can be loaded rapidly into the xylem by transport to the above-ground tissues. Once Cd has entered into the cytosol, it can bind to phytochelatins or their precursor glutathione, generating conjugates that can be transported into the vacuoles, preventing the free circulation of Cd ions in the cytosol (Cobbett 2000 Verbruggen et al. 2009). Cd can also be complexated by metallothioneins and nicotianamine (Cobbett and Goldsbrough 2002 Sharma and Dietz 2006). Proline, histidine and polyamines are also involved in the...

Cell Wall Binding and Vacuole Sequestration

After Cd enters the cytosol, some mechanisms may play roles to inactivate it through chelation or conversion to a less toxic form. Phytochelatins could bind Cd2+ in the cytoplasm, and Cd transport into the vacuole is an effective way to reduce the levels of Cd toxicity in the cytosol. No doubt, an efficient tonoplast transport of Cd is very important. Several families of transporters may take part in the process of vacuole sequestration, such as YCF1, MTP1, and CaCA (see Sect. 2.2 for details).

Agroclavine 17hydroxylase

Cytochrome P-450 mono-oxygenase (non-inducible with liver enzyme inducers) catalysing exclusively the conversion of agroclavine to elymoclavine. The enzyme is located in the 15000-105000 g-fraction. NADPH and molecular oxygen were required for its activity. Under optimised condition 16 conversion was reached within one hour of incubation. The enzyme did not catalyse the conversion of DMAT to OH-DMAT that is apparently a non-specific reaction leading to elymoclavine catalysed by broad specificity oxygenases of Claviceps (Petroski and Kelleher, 1977 Saini and Anderson, 1978). Agroclavine hydroxylase activity was inhibited by carbon monoxide, but not by cyanide or EDTA that is typical for a cyctochrome P-450 monooxygenase. There is also a good correlation between alkaloid production and the enzyme activity. Practically comparable results concerning agroclavine hydroxylase (which they named agroclavine 17-mono-oxygenase) were obtained by Maier et al. (1988). They showed that agroclavine...

Metallomics And Metallomes

Organic acids play a role in metal chelation by forming complexes with metals, a process of metal detoxification. Chelation of metals with exuded organic acids in the rhizosphere and rhizospheric processes indeed form an important aspect of investigation for remediation. These metabolic pathways underscore the physiological, biochemical, and molecular bases for heavy metal tolerance 6 .

Siderophoremediated Iron

Structural properties of chrysobactin have been studied in detail (Persmark et al., 1989). Chrysobactin, identified as dihydroxybenzoyl)-D-lysyl -L-serine, belongs to a class of siderophores which are basically dihydroxybenzoic acid (DHB) derivatives of amino acids or peptides. Unlike the tricatecholate siderophore enterobactin and other hexadentate ligands, which are strong Fe binders, chrysobactin possesses only three potential coordination sites for complexing ferric Fe, two hydroxyl groups on the catechol moiety and the terminal carboxylate group of serine. Persmark and Neilands (1992) have shown that only catecholate hydroxyl groups are involved in the chelation suggesting that chrysobactin is a bidentate ligand, and thus a relatively weak ligand. However, depending on the pH and metal ligand concentration ratio, chrysobactin was found to form ferric complexes of different stoichiometries, from 1 1 to 1 3 (Fe chrysobactin). When ligand is four or more times in excess, there is a...

And Achromobactindependent Iron Transport

A first approach based on cloning and complementation tests using E. coli mutants defective in enterobactin production allowed the genetic region involved in chrysobactin-mediated Fe transport to be identified. Using a collection of mutants that were unable to grow in the presence of EDDHA, it was possible to characterize the different stages required for biosynthesis of chrysobactin and the transport back to the cell of its ferric complex (Enard et al., 1988). The genetic organisation of the chrysobactin system is reminiscent of that of the enterobactin region in Escherichia coli K12. It comprises four operons divergently transcribed from two bidirectional promoters (Figure 10-2). The fct-cbsCEBA operon encodes the receptor Fct and the enzymes leading to the DHB moiety in chrysobactin biosynthesis (Franza and Expert, 1991). A second operon, cbsHF, encodes chrysobactin synthase CbsF, which is predicted to be a nonribosomal peptide synthetase with a multimodular structure allowing the...

Role Of Pcs In Detoxification Of Heavy Metals Other Than Cadmium

Because plants assimilate various metal ions from soil, the first organ exposed to these ions is the root. Localization of PC synthetase to roots and stems probably provides an effective means of restricting the heavy metals to these organs by chelation in the form of Cd-PC complexes. It has been demonstrated that PCs are able to protect enzymes from heavy metal poisoning in vitro 65,132 many metal-sensitive plant enzymes (rubisco, nitrate reductase, alcohol dehydrogenase, glycerol-3-phosphate dehydrogenase, and urease) were more tolerant to Cd in the form of a Cd-PC complex compared with the free metal ion. Free PCs could reactivate the metal-poisoned enzymes (nitrate reductase poisoned by Cd-acetate) in vitro more effectively than other chelators such as GSH or citrate 65 .

The Factors Affecting In Planta Spectra of Screening Pigments and Radiation Screening Efficiency

The spectra of vacuole-contained pigments can be changed significantly as a result of intra- and intermolecular copigmentation, the formation of various complexes, and the effects of pH, metal ion chelation, tautomerism, etc. (Asen et al. 1972 Lancaster et al. 1994 Smith and Markham 1998). These effects lead to a significant hyperchromic effect and profound bathochromic shifts in the absorption spectra of vacuolar contents.

Isolation of Nuclei and Protein Extraction

The nuclei were prepared from chickpea seedlings as described 20 . About 20 g of the tissue was ground into powder in liquid nitrogen with 0.3 (w w) PVPP and immediately transferred into an ice-cold 500-mL beaker containing 200 mL of ice-cold 1X HB (10 mM Trizma base, 80 mM KCl, 10 mM EDTA, 1 mM spermidine, 1 mM spermine, 0.5 M sucrose, pH 9.5) plus 0.15 2-ME and 0.5 Triton X-l00. The contents were gently stirred for 30 min for complete lysis of organeller membranes. This suspension was filtered through four layers of cheesecloth and two layers of Mira cloth into an ice-cold 250-mL centrifuge bottle. The homogenate was pelleted by centrifugation with a fixed-angle rotor at 1800g at 4 C for 20 min. The supernatant fluid was discarded and the pellet was gently resuspended in 30 mL of ice-cold wash buffer (1X HB minus Triton X-100). To remove the particulate matter remaining in the suspension, the resuspended nuclei were filtered into a 50-mL centrifuge tube through two layers of Mira...

Ectomycoremediation of Heavy Metals

Depending on the conditions, the utilization of mycorrhizal systems can assist the phytoremediation of heavy metal polluted soils by the positive effect of ECM fungi on plant tolerance, but could also limit the plants ability to extract heavy metals from the soil by reducing the uptake and the transfer into the shoot. The colonization of tree species with ECM fungi is often essential for the reforestation of old mine sites, because ECM fungi are able to ameliorate the toxicity of heavy metals (Marx 1975). On the other hand, ECM fungi have been shown to enhance the uptake of metals by plants particularly when the exogenous supply is low (Colpaert and Van Assche 1992), but can also reduce the uptake into the plant and the transport into the shoot when the external supply is high (Buucking and Heyser 1994 Krznaric et al. 2009). Several mechanisms have been described to be involved in the reduced heavy metal uptake of ECM plants (1) the larger cell wall surface that can bind heavy metals,...

Caesium chloride density gradient ultracentrifugation

(a) Solution 1-1.0 m CsCl (density 1.12 gml-1), 50 dim Tris-HC1 (pH 8.0), 10 mM EDTA, 200 xg ethidium bromide ml-1 (b) Solution 2-6.6 m CsCl (density 1.82 gml-1), 50 mm Tris-HC1 (pH 8.0), 10 mM EDTA, 0.1 n-lauroyl sarcosine (c) Solution 3-4.5 m CsCl (density 1.55 gml-1), 50 mm Tris-HC1 (pH 8.0), 10 mM EDTA, 0.1 n-lauroyl sarcosine, 100 xg ethidium bromide ml-1.

Summary And Conclusions

Tests conducted using carbamoylphosphonate-functionalized nanoporous substrates (APH and PPH SAMMS) showed that these sorbents very effectively adsorbed Pu(IV) from solutions containing complexing ligands, such as EDTA, citrate, phosphate, sulfate, and nitrate. Distribution coefficients as high as 2 x 104 ml g confirmed that the CMPO-based functionalities assembled on nanoporous substrates are very effective scavengers for actinide ions such as Pu.

Iron Uptake From The Soil

Grasses depend on an Fe chelation-based Fe mobilisation mechanism, that involves phytosiderophore production and import of Fe(III)-phyto-siderophore complexes (Strategy II, reviewed by Mori, 1999). The major genes for phytosiderophore production and a phytosiderophore transporter YS1 ( YELLOW STRIPE 1) have been biochemically, genetically or transgenetically analyzed in different grass species see Curie and Briat (2003), Mori (1999) and reviews in this book for details on the genetic basis for phytosiderophore production see Curie et al. (2001), Schaaf et al. (2004) and Roberts et al. (2004) for details about maize YS1 .

Subfractionation of Mitochondria

The subfractionation of mitochondria into the four basic compartments involves a combination of osmotic shock and differential centrifugation. Isolated mitochondria that have not previously been frozen are suspended in a low osmotic strength solution (0-50 mM sucrose, 2 mM EDTA, 10 mM MOPS, pH 7.2). The solution is gently stirred on ice for 15 min to osmotically shock mitochondria. The molarity of the solution then needs to be increased to 0.3 M sucrose by the slow addition with stirring of 2 M sucrose, 2 mM EDTA, 10 mM, pH 7.2 stock solutions. The solution is then centrifuged at 15,000g for 15 min at 4 C to pellet the mitoplasts comprising the inner membrane and matrix (IM and MA). The mitoplast may be stored frozen for fraction-ation at a later stage. The supernatant containing the outer membrane (OM) and the intermembrane space (IMS) is transferred to clean tubes and centrifuged at 200,000g for 90 min. The resulting supernatant contains the IMS and is removed and stored frozen. The...

Intracellular Iron Transport

Storage of excess Fe bound to ferritin. Iron import into chloroplasts is apparently carried out by uniport-mechanism in a non-specific mechanism, as suggested by successful competition of Fe transport by other micronutrient ions (Shingles et al., 2002). The nicotianamine-free chloronerva mutant accumulates Fe precipitates in the chloroplast, but contains no detectable ferritin (Liu et al., 1998 Becker et al., 1995), suggesting that nicotianamine is a prerequisite for transport between chelation in the cytosol and proper storage in target compartments. Mitochondria are another target for Fe, mostly in Fe-sulfar clusters. An Arabidopsis mutant lacking a mitochondrial ATP binding cassette transporter shows increased contents of non-heme and non-protein bound Fe, together with increased expression of genes encoding oxygen radical detoxifying enzymes (Kushnir et al., 2001). Frataxin is important for maintenance of mitochondrial Fe levels. Loss-of-function frataxin mutants show altered...

An Evolutionary Proposal

Aged widespread recruitment of iron as a cofactor in biological redox chemistry. By contrast, under oxidizing conditions ferric iron is poorly soluble 9 . Today, all multi-cellular and, essentially, all single -cell organisms require iron for growth, despite the biological availability of iron being extremely limited by the insolubility of iron hydroxide. This is the reason why microbes synthesize low-molecular weight chelating agents, called siderophores, to bind and solubilize iron. Such ferric siderophore complexes are then transported into the bacteria by specific receptor proteins. In fact, competition for iron between a host and a bacterium is an important factor in determining the course of a bacterial infection. Because of that, different organisms utilize structurally varied siderophores to also competitively bind iron and gain selective growth advantages. Such competition even occurs in mammals where dietary iron is absorbed and bound to transferrin, the iron transport...

Lead Acquisition And Transport

Accumulation of Pb by plants depends on several factors, the most important of which are the genetic capability of the plant, as in a hyperaccumulator, and Pb bioavailability. The limiting factor for metal accumulation is the amount of Pb readily available for uptake. The solubility of Pb in soil is limited due to complexation with organic matter, sorption on clays and oxides, and precipitation as carbonates, hydroxides, and phosphates 27 . The application of a synthetic chelator has been used to increase Pb solubility in soil solution and EDTA has been found to be a most effective chelating agent for Pb desorption 7,8,28 . The chemistry and physiology of EDTA-Pb complex is understood better than that of any other Pb-chelate complex. When EDTA is added to Pb-contaminated soil, it complexes with soluble Pb. Due to high affinity of EDTA for Pb, the Pb-EDTA complex formation dominates other metal-EDTA complexation in most soils between pH 5.2 and 7.7 29 . The soluble soil Pb...

Concentration of iron in xylem sap of barley fed with ironIII and chelators

Takagi (1984) reported that PS could enhance Fe translocation to the shoot more rapidly than EDTA in rice fed with FeCl3 (20 M). It has been verified that PS are much more effective to enhance the absorption of Fe than the other natural or artificial chelators (Marschner et al., 1986 Romheld and Marschner, 1986). Our preliminary results (Kawai et al., 2001) reported that PS enhanced Fe concentration in xylem sap more than the synthetic chelator EDTA. Figure 14-7. Metal concentrations in xylem sap collected from barley grown hydroponically with different concentrations of EDTA-Fe (0, 1, 10, 100 M). Figure 14-7. Metal concentrations in xylem sap collected from barley grown hydroponically with different concentrations of EDTA-Fe (0, 1, 10, 100 M). As a follow-up research, an experiment was conducted to examine whether PS could enhance Fe concentration in xylem sap more than other Fe chelators, when fed to the roots together with Fe3+. Roots of barley plants grown hydroponically under -Fe...

Incubate at 60C for the desired length of time calculated as follows

Proteinase K buffer 100 mM Tris 50 mM EDTA (pH 7.5) Proteinase K 20x SSPE Dissolve 175.3 g of NaCl, 27.6 g of NaH2P04.H20, and 7.4 g of EDTA in 800 ml of H20. Adjust the pH to 7.4 with NaOH and the volume to 1 liter with H20. 5. Digest with proteinase K as follows Warm the proteinase K buffer (100 mM Tris, 50 mM EDTA, pH 7.5) to 37 C. Prepare a fresh proteinase K solution of 5 mg ml, and dilute this solution in warm buffer to a final concentration of 1 Jig ml. Submerge the slide in the solution and incubate for 30 minutes at 37 C.

The translocation of the metals in xylem sap of barley

The chelators PS, FOB, and EDTA were dissolved in the hydroponic media (25 M) and supplied to the root of +Fe or -Fe barley plants for 3 hours in the afternoon. Xylem sap was collected for 3 hours after the supply of chelators (Alam et al., 2001a). Table 14-3 shows the amount of metal micronutrients translocated in xylem sap. It was apparent that feeding with PS largely enhanced the amount (pmol plant-1 h 1) of Fe translocation in xylem tubes of -Fe barley. Feeding with FOB also enhanced Fe translocation slightly. Feeding with EDTA, - EDTA

Interaction of Metals with Nucleic Acids

In general metals can interact directly or indirectly with nucleic acids. The numerous nucleophilic centres in nucleic acids are favourite binding sites for metal ions. The type and localisation of binding apparently depend on the metal considered. Induction of crosslinks between both DNA strands, single-strand DNA breaks and chelation or formation of complexes between DNA and metals were described (see Gebhart and Rossman, 1991, for a review). Similar reactions can also be expected between metals and RNA, thereby affecting the specific functions of the latter.

Cell Wall Polysaccharides

Caused by the activity of pectin methyl esterases secreted at the apex (Li et al. 2002). A distribution of methyl-esterified pectins similar to the one in an-giosperms was observed in gymnosperm pollen tubes (Derksen et al. 1999a). In Pinus, no acidic pectin was found in the pollen tube except for the site where the inner intine of the pollen grain stretches over the pollen tube. Fluctuations in the growth rate cause the density of pectins to change along the longitudinal axis of the tube resulting in the appearance of more or less regularly spaced rings (Fig. 3). It should be noted that these fluctuations in pectin density are not accompanied by overall changes in cell wall thickness (Geit-mann et al. 1995 Pierson et al. 1995), but after EDTA extraction periodic alternations of material with different material properties are revealed in the scanning electron microscope (Derksen, personal communication).

Probe Synthesis Materials

Reagents for in vitro transcription and DIG labeling RNase inhibitor RNase-free DNase lOx DNase buffer (100 ml) 40 ml of 1 M Tris (pH 7.5) 6 ml of MgCl2 54 ml of distilled H20 Adjust pH to 7.5. Equipment for agarose gel electrophoresis of RNA EDTA (0.5 M) LiCl (4 M) Ethanol 0.5 m EDTA 2 pi Proteinase K (10 mg ml in 0.1 M Tris-Cl pH 7.5 , 0.05 M EDTA 4. Rinse with distilled H O and then transfer to 10 pg ml proteinase K in 0.1 M Tris-HCl pi 7.5 , 0.05 M EDTA pH 8.0 ) for 30 minutes at 37 C. Warm the buffer to 37 C before adding the proteinase K.

Evidence that NR inactivation requires NRphosphorylation and 1433binding

Apparently divalent cations were required to keep NR in its inactivated state . NR activity from light extracts could be rapidly decreased in vitro by incubation with MgATP. Based on such observations, we suggested already in 1991 that NR was probably inactivated by protein phosphorylation (Kaiser and Spill 1991). Subsequently, Huber et al. (1992) and MacKintosh (1992) presented direct evidence that NR was indeed more phosphorylated in dark than in light, consistent with the activity measurements. Some years later, a Ser-543 residue in the hinge 1 region was identified as the site of regulatory phosphorylation (Douglas et al. 1995, Bachmann et al. 1996a, Su et al. 1996).

Physiological Aspects of Radionuclide Absorption by Plant Roots

0.1) (Dahlman et al., 1976) although it can be seen from Table 7-14 that TF values for this element are commonly six orders of magnitude lower than this. In practice the predominant pathway of plant contamination by actinide elements is usually direct contamination due to the deposition and resuspension processes covered in the previous section. In a summary of data collected on plant root uptake from contaminated sites up to 30 years after nuclear weapons testing Dahlman et al. (1976) concluded that the vast majority of these elements remained within the soil, associated at least in part with humic substances. Concentration ratios (soil-to-plant transfer factors) were invariably 1 in unamended soils and showed a very high degree of variability (up to eight orders of magnitude - see Fig. 7-12). Interestingly, the addition of artificial chelating agents such as DTPA increased the root uptake of Pu in these studies, probably by increasing the fraction of monomeric Pu in the soils and...

Consequences of NR inactivation on NR kinetics

Binding of 14-3-3 to P-NR has been shown to interrupt whole-chain electron transfer from NADH to nitrate, and the partial activity from the electron donor methylviologen (MV) to nitrate was also blocked (Bachmann et al. 1996a). Most probably, 14-3-3-binding causes a conformational change which inhibits electron transfer from the heme-Fe of the Cyt b moiety to MoMPT. That conformation change may prevent the cationic MV electron donor to interact. Interestingly, the Km values for NADH (1 to 7 pM) and nitrate (20 to 40 pM) are not changed by the above inactivation mechanism (Kaiser and Spill 1991). Thus, phosphorylation and 14-3-3 binding do not change kinetic properties of the enzyme, but only the ratios of free NR (active) to P-NR-14-3-3 complexes (inactive). Neither in leaves nor in roots was NR activity ever completely abolished or fully activated by the above modulation. In fact, as a general rule, a very low activation state in darkened leaves is about 20 (of total NR activity...

Laboratory Culture Systems

For the quartz sand cultures, the brownish 'aquarium sand' is acid-washed before use. Sand culture pots are soaked with a nutrient-poor 'Geosiphon medium' (GM32) 0.1 mM MgSO4, 0.2 mM Ca(NO3)2, 0.1 mM KCl, 1 pM K2HPO4,12 pM FeCl3,12 pM Na2-EDTA, 0.08 pM ZnSO4,0.9 pM MnCl2,16.2 pM H3BO3,0.04 pM CoCl2,0.08 pM Na2MoO4,0.01 pM CuSO4, 0.01 pM NaHSeO3, 0.01 pM NiCl2, 0.01 pM Na3VO4, 0.005 pM K2Cr2O7, 0.5 mM MES, pH 6.0 (KOH-titrated). We currently also add KBr (0.1 pM 'GM33'). The sand cultures do not work without a thin charcoal layer scattered at the surface (Figs. 1,2 and 3).

Cytosolic ion concentrations

Cytosolic ions may be further factors involved in the control of NR activity. Artificial acidification of darkened leaf or root pieces with permeating weak acids and low external pH activated NR, and alkalinisation with permeating bases and high external pH reversed this effect (Kaiser and Brendle-Behnisch 1995). Further, treatment of darkened leaf discs with EDTA and the ionophore A23187, also activated NR (Kaiser and Huber 1994). Unfortunately, this does not necessarily prove direct Ca2+ effects e.g. on protein kinases (CDPKs). Efflux of divalent cations may be connected to a proton influx, and NR activation may thus also be related to cytosolic acidification.

Nondenaturing Gel Electrophoresis Of Proteins

The protein extraction procedure is the same as that for regular SDS-PAGE, but the buffers lack EDTA, SDS, and (3-mercaptoethanol, and the samples are not boiled prior to loading. Please note that depending on the nature of the protein, the initial preparation may need to be done under altered conditions. This protocol was developed for a light-labile protein complex, which requires the use of a green safelight.

Membrane Preparation For Receptor Binding Studies

Porcine brains, which were obtained within 30 min after death of the animals from a local slaughterhouse, were used to prepare receptor-rich membranes. The brains were immediately frozen in liquid N2 50 g brain per 200 mL ice-cold buffer (0.32 M sucrose, 10 mM potassium phosphate buffer, pH 7.0, 1 mM EDTA) were homogenized twice for 15 sec in a blender and then for 1 min with an ultraturrax. The homogenate was centrifuged three times for 15 min at 1.400 g and 4 C to separate cellular debris. The supernatant was spun down at 100.000 g for 60 min. The resulting pellet was resuspended in buffer (as above but without sucrose). Aliquots were stored frozen at -80 C. Protein content was determined by the Lowry method, using bovine serum albumin as a standard.32-35

Effect of Other Additives on Antimicrobial Activity

The materials examined included EDTA, oil of thyme, propylene glycol and butylene glycol. All materials were examined in a range of concentrations, and it was found that none of the materials examined had any observable effect on the anti-microbial activity of the oil.

Metal And Mineral Transformations

The ability of microorganisms to influence metal speciation in the soil results from indirect and direct properties which influence the balance of metal species between soluble and insoluble phases (Figures 2.1 to 2.3). Mobilization of metals can be achieved by various mechanisms protonation, chelation, and chemical transformations. Metal immobilization can occur by precipitation or crystallization of insoluble organic or inorganic compounds (e.g., oxalates and sulfides, respectively), or by sorption, uptake, and intracellular sequestration (Glasauer et al., 2004a). In addition, redox reactions can mobilize or immobilize metals, depending on the particular metal species and microenvironment (Figure 2.2).

Uptake Translocation and Deposition of TEs Within the Plant

Undoubtedly, metal chelation and or compl-exation with in organic ligands enhance desorption from soil solids, and having mobilised TEs into a dissolved phase, improve their root uptake phytoaccumulation, although underlying mechanisms are unclear. Uptake of metals from the rhizosphere is mediated by a specific (Cu, Fe, Zn) and or nonspecific (e.g. Cd) transporter proteins embedded into the plasma membrane of root cells (e.g. see review by Clemens 2006). Due to similar physical (ionic radius) and chemical (redox-activity, Lewis acidity) properties among TEs, non-essential and highly toxic ones (e.g. Cd) most probably enter roots via highly specific routes for essential nutrients (e.g. Zn), especially under stressful conditions (e.g. Ondrasek et al. 2009a) .

And Chemical CaMg Ratio LMWOAs Factors Influencing Phytoremediation Efficiency

The rhizosphere, as the space in the immediate vicinity of roots, is permanently influenced by their exudates. Moreover, it differs - in relation to other soil fractions - in the composition and large amounts of bacterial cells (the phenomenon of bacteriolysis) and fungi (mycorrhiza), with diversified decay of plant roots, soil structure, composition of organic matter, pH, humidity and microorganism activity. The properties often change in a particular site, demonstrating frequently dynamic changes in time (Macek et al. 2007) . All the above-listed factors influence the solubility and uptake of pollutants, both indirectly, through the change of their microbiological activity and the root growth dynamics, and also directly through changes of soil reactions, chelation, precipitation of deposits and oxidation-reduction reactions.

Fractionation studies

Plants may produce a measurable Fe-isotopic fractionation because Fe trafficking involves a number of steps, such as reduction by enzymes, transport across membranes, chelation by small organic compounds or proteins, etc. (Marschner, 1995), and these mechanisms may have different rates with different Fe isotopes. Experiments with dissimilatory Fe-reducing bacteria of the genus Shewanella algae grown on a ferrihydrite substrate indicate that the 856Fe of Fe(II) in solution was isotopically lighter than the

Other Isotopes That Can Be Important In Plant Iron Research

Carbon radioisotopes such as 14C and 11C have also been used in plant Fe research. Carbon-14 was used to study the plant uptake and breakdown of synthetic Fe(III) chelates by Hill-Cottingham and Lloyd-Jones (1961) and Jeffreys et al. (1961), using 14C labelled EDTA and EDDHA to synthesize 59Fe-14C-labeled Fe(III)-EDTA and -EDDHA. These dual-labelled Fe-chelates were used to investigate the uptake of the whole organic molecule by roots (Hill-Cottingham and Lloyd-Jones, 1961). Recently, a protocol to incorporate 14C into nicotianamine, a non-proteinogenic amino acid considered to be a key component in Fe homeostasis in plants, has been developed by Schmiedeberg et al. (2003), using the precursor S-adenosylmethionine labelled with 14C and a recombinant nicotianamine synthase. Also, studies with 14C were made to identify maize root exudates involved in Fe trafficking in the rhizosphere and to estimate their amount (Kuzyakov et al., 2003). Maize plants were labelled in a 14CO2 atmosphere...

Mean Cu and Zn Concentrations Extracted Using Mehlich 3 Reagent from Control Soils 0 years and from Soils after 10

The leaching of Cu and Zn to subsoil depths has been explained by metal chelation with soluble organic compounds from the litter 80,81 . It appears that the highest trace metal concentrations in manure-treated fields are measured in topsoil. By extracting subsoils and finding an increase in Cu and Zn concentrations, scientists have suggested that some downward leaching of Cu and Zn can occur in manure-treated soils. Measured subsoil concentration increases are, however, small. Nevertheless, lack of substantial Cu and Zn concentrations in subsoil depths cannot exclude the fact that soluble forms of trace metals can leach through the soil profile and could cause enrichment in shallow ground water. Trace metal enrichment of shallow ground water as a result of leaching has not been sufficiently documented in soils treated with animal manures. Additional studies examining trace metal concentrations in shallow ground water beneath manure-treated fields should be conducted to determine...

Quality Of Commercial Iron Chelates

Eddha Production

Commercial products are obtained by carrying out first the industrial synthesis of the chelating agents and then incorporating Fe from inorganic salts. While the first synthesis pathways proposed produced quite pure compounds (Kroll et al., 1957), the industrial synthesis pathways used nowadays (Dexter, 1958 Petree et al., 1978) yield commercial products with quite different purities, and also lead to the presence of by-products. For instance, the condensation product 2,6-di CH(COOH)NHCH2 CH2NHCH(COOH)Ar phenol (Ar) hydroxyphenyl (Cremonini et al., 2001) and o,p-EDDHA (G mez-Gallego et al., 2002) have been detected in EDDHA commercial products, by using one- and two dimensional nuclear magnetic resonance and ion pair HPLC. Also, main impurities in the EDDHSA Fe3+ and EDDCHA Fe3+ containing products have been studied by HPLC ( lvarez-Fern ndez et al., 2002a), revealing that unreacted starting materials (p-hydroxybenzenesulfonic acid and p-hydroxybenzoic acid, respectively) were always...

Chlorophyll mg g1 fw 208 017 074 025 021 021

Reduction of Fe3+-WEHS or Fe3+-EDTA (1 M Fe) by intact roots of Fe-sufficient (+Fe) and Fe-deficient (-Fe) cucumber plants (data from Pinton et al., 1999a). Table 7-3. Reduction of Fe3+-WEHS or Fe3+-EDTA (1 M Fe) by intact roots of Fe-sufficient (+Fe) and Fe-deficient (-Fe) cucumber plants (data from Pinton et al., 1999a). Fe3+-EDTA

Variations in Heavy Metal Tolerance in Plants

Metal tolerance may be achieved by metal chelation with high-affinity ligands inside and outside the cytoplasm. In Alyssum lesbiacum, Ni accumulation was associated with a large and proportional increase in xylem concentrations of the free amino-acid histidine, which was proposed to reflect an increase of intracellular, most probably cytoplasmic histidine concentrations. Furthermore, it was demonstrated that histidine binds Ni in vivo and that exogenous application of histidine reduced Ni toxicity in the nontolerant species Alyssum montanum (Kramer et al. 1996). However, the histidine response is unlikely to provide oxidative protection, since histidine com-plexation of Ni is known to enhance oxidative DNA damage induced by the metal in vitro (Datta et al. 1992, 1993 Misra et al. 1993). This suggests that once the metal has entered the plant cell, high affinity chelation, targeting, and sequestration of the metal chelate are all vital for metal tolerance. Accumulation of Cd in the...

Interaction in the rhizosphere

Undoubtedly, heavy metals compete with Fe for organic ligands. Although Fe3+ forms the most stable chelates as compared with divalent heavy metal ions, after reduction of Fe3+-chelates at the outer surface of the root cell plasmalemma in dicotyledonous plants the released free chelating agents may chelate other metals such as Pb2+ or Cd2+ if no more free Fe3+ ions are available (Srivastava and Appenroth, 1995). The competition would also depend on the stoichiometry of competing ions. Table 6-1. Stability of some metal chelate complexes presented as logK for the equation Men+ + Lm- MeL(m-n)-. (L EDTA, ethylenediamintetraacetic acid citrate MA, mugineic acid DMA, deoxymugineic acid NA, nicotianamine). Table 6-1. Stability of some metal chelate complexes presented as logK for the equation Men+ + Lm- MeL(m-n)-. (L EDTA, ethylenediamintetraacetic acid citrate MA, mugineic acid DMA, deoxymugineic acid NA, nicotianamine). EDTA1 Metal ions are first adsorbed by the root cell wall carbohydrate...

Equilibrium Models Concentration Ranges and Biological Functions of Metal Ions

Produce agents which trap them by chelation (induction of phytochelatins). Accordingly, these data (BCF, intra-and interspecific organismal distributions) for Cd, Hg or U in plants or animals are more difficult to attribute to purely chemical features of transport, because here (and with As, Pb, Ni) there is superposition of

S100 Proteins S100 A89 Calprotectin and S100A12 Calgranulin C

The heterodimeric complex of the two Ca2+-binding S100 proteins S100A8 and A9, also known as calgranulin A and B or calprotectin, exhibits selective biostatic activity at high concentrations against C. albicans (Murthy et al. 1993). Zinc chelation was proposed as a potentially important host defense function of calprotectin (Clohessy and Golden 1995) and it was shown that intact calprotectin, consisting of both subunits, is necessary to form a zinc-binding site capable of inhibiting microbial growth (Sohnle et al. 2000).

Utilization of microbial siderophores by plants

Iron uptake from siderophores by Strategy I plants has been examined for the hydroxamate siderophores ferrichrome, ferrioxamine B, rhodotorulic acid, and the mixed ligand siderophore pseudobactin produced by Pseudomonas spp. Other siderophores that have been studied and shown to be relatively effective for delivery of iron to plants include rhizoferrin, a citrate based siderophore produced by the fungus Rhizopus, and fusarinines, also produced by fungi. As a basis for comparison, iron uptake from siderophores is normally compared to that measured with supply of iron from synthetic chelates such as EDTA and HEDTA (Walter et al., 1994 Johnson et al., 2002). In general, iron acquisition from these compounds requires relatively high micromolar concentrations in hydroponic solutions where the entire root system is bathed in a uniform concentration of the siderophore. The utilization of siderophores that are used by extracellular reduction is sensitive to the presence of excess deferrated...

Enzyme characterization and assay procedures

Nitrate reductase (NR) is a labile enzyme and for this reason a number of protectants are added to the extraction media (Wray and Fido, 1990). These protectants usually include nitrate, which is an NR substrate FAD, which is a prosthetic group present in the protease-sensitive region of NR EDTA, which chelates toxic metals released during cell breakage and sulphydryl compounds such as dithiothreitol and mercap-toethanol, which prevent the oxidation of essential SH-groups of NR. Protease inhibitors such as phenylmethylsulphonyl fluoride are usually added to inhibit proteolysis during extraction. Exogenous proteins such as bovine serum albumin and casein are routinely used to enhance the stability of NR. A detailed study of in vitro measurement of NR in the basidiomycete Hebeloma cylindrosporum has been carried out by Plassard et al. (1984a). NADH-linked GDH of higher plants is a metalloprotein and requires added calcium to prevent inactivation by EDTA or other chelating agents. No...

Mechanisms of Metal Tolerance in ECMF

Metal tolerance may be defined as the genetically conditioned ability to grow and reproduce in environments with high concentrations of potentially toxic metals (Hartley et al. 1997). A metal-tolerant organism must be able to maintain metal homeostasis in the presence of high metal concentrations, controlling the concentrations of free metal ions in the cytosol. A multitude of mechanisms were proposed to contribute to metal tolerance in ECMF (Hartley et al. 1997 Leyval et al. 1997). Avoidance mechanisms reduce the exposure of ECMF cells to toxic metals and limit metal entry into the cell (Gadd 1993 Hartley et al. 1997). Avoidance mechanisms include the extracellular biochemical transformations of metals discussed above and the regulation of metal uptake extracellular ligation of metal ions to di- and tricarboxylic acids and chelation with siderophores extracellular metal immobilization by adsorption to cell walls, pigments and extracellular polysacchar-ides (fungal slimes)...

Of xylem sap of barley and rice grown hydroponically under varied concentrations of iron

As shown in the previous section 4.1, the concentration of PS was much higher than that of Fe in xylem sap of -Fe barley. The ratio of the concentration of PS Fe varied depending on Fe nutritional status of the plant. In order to obtain data for the PS Fe ratio as affected by the Fe status of the plant, the xylem sap from grasses grown with various concentrations of Fe (0, 1, 10, 100 M) in hydroponic culture was collected and analyzed. Iron sources in the hydroponics media for barley and rice were EDTA-Fe (Kawai et al., 1993) and citrate-Fe (Alam et al., 2003), respectively. Table 14-2. Amounts and ratios of phytosiderophores and Fe of xylem sap of barley and rice. Xylem sap was collected for 3 hours from 36 plants of barley or 96 plants of rice grown hydroponically in a greenhouse. Iron sources for the cultivation were EDTA-Fe for barley and citrate-Fe for rice. Table 14-2. Amounts and ratios of phytosiderophores and Fe of xylem sap of barley and rice. Xylem sap was collected for 3...

PH Changes in the Rhizosphere and Bioavailability of Trace Elements

Bernal et al. 32 compared redox potential and pH changes in the rhizosphere of the Ni hyperaccumulator Alyssum murale and the nonhyperaccumulator Raphanus sativus. These workers concluded that the form of N taken up by the plants was the main factor responsible for pH changes and that the plants were able to reduce system more effectively than the hyperaccumulator. These results indicate that the hyperaccumulator mechanisms may be due to other rhizosphere processes, such as the release of chelating agents, or to differences in the number and affinity of metal root transporters. McGrath et al. 33 studied the heavy metals uptake and chemical changes in the rhizosphere of Thlaspi caerulescens and Thlaspi ochroleucum grown in contaminated soils. Knight et al. 34 investigated the Zn and Cd uptake by the hyperaccumulator Thlaspi caerulescens in contaminated soils and its effects on the concentration and chemical speciation of metals in soil solution. They found that the decrease in the...

Arbuscular Mycorrhizae and Soil Pollution

It is well known that AM fungi can alter metal concentrations and induce increased tolerance in plants, and different mechanisms have been proposed to explain this the binding of metals to fungal cell walls and subsequently being accumulated in the vacuoles sequestration by sidero-phores, deposited in the root apoplasm or in the soil, and possibly taken up by plant ferrisidero-phore receptors, or complexing of metals to met-allothioneins or phytochelatins synthesized by the fungus or the plant, as well as organic acids, amino acids, and metal-specific chaperons (shown for plants, but assumed for AM fungi) (Miransari, 2010) or metal chelation by fungal compounds, such as glomalin (Hildebrandt et al. 2007 Bedini et al. 2009).

Conclusion And Future Outlook

In the future, research should focus on the synthesis and characterization of new Fe chelating agents, selected not only on the basis of a high stability constant but also according to their capability to deliver Fe to the plant and on the possibility to produce highly pure commercial products at a lower cost.

Zinctransporting Genes In Plants

Citrate was not shown to play an important role in Zn chelation and malate had constitutively high concentrations in the shoots of the accumulator T. caerulescens and the nonaccumulator T. ochroleucum. More recently, direct measurements of the in vivo speciation of Zn in T. caerulescens using the noninvasive technique of x-ray absorption have revealed that histidine is responsible for the transport of Zn within the cell, whereas organic acids (citrate and oxalate) chelate Zn during long-distance transport and storage. Another constitutive aspect of T. caerulescens is the high Zn requirement for maximum growth, compared to other species. This probably depends on the strong expression of the metal sequestration mechanism, which would subtract a large amount of intracellular Zn to normal physiological processes even when the Zn supply is low.

Further Transport of Metal Ions Inside Plants

Homeostasis Plants

For selectivity of binding of metal ions, binding to carriers and its selectivity are relevant. Some ligands, production rates of which may be increased upon metal exposition, like nicotianamine (Fe, Cu), histidine (Ni), or citrate (Cd, Al) increase carryover of the said metal ions into the xylem in both hyperaccumulators and normal plants as do chelators which are not altered by metabolism, e.g. EDTA, when they are added to the soil. There is a difference in structure whereas in albumines four histidines (or two histidines and two car-boxamides) are located at one end of the peptide sequence, they form a bridge between two helices in IRT-1 (Grossoehme et al. 2005). The limited complex formation stabilities of these ligand site arrays, allowing for reversible binding rather than the role of some cation trap , is just suited for transportations tasks. Amino acids may extract the metal ions from this carrier (also others than Ni) by forming more stable complexes as is done in isolation...

Heavy metal availability in the soil

Since Fe chlorosis is a serious agricultural problem in certain areas, many procedures have been developed to increase soil Fe availability. One of these is the application to the soil of synthetic chelating agents (Garc a-Marco et al., 2003). As chelating agents bind Fe and other heavy metals, they may be used for increasing the solubility and phytoavailability of toxic metals for decontamination purposes (see below). The application of CDTA or DTPA caused a shift in the distribution of Pb in the soil from more recalcitrant to more soluble forms, greatly increasing the leaching of this metal (Cooper et al., 1999). EDTA, which has a high stability constant with Fe3+, also enhances Pb solubility (Blaylock et al., 1997 Huang et al., 1997). However, EDTA application to soils may result in long-term solubilization of heavy metals. For instance, in a study with two metal contaminated soils, Cu-EDTA and Cd-EDTA complexes were still found in soil pore water 5 months after the application of...

Uptake transport distribution

Information about the mechanism involved in secretion of MA-phytosiderophores into the rhizosphere, wherein they solubilize the sparingly soluble Fe3+ by chelation, is rather limited. According to Sakaguchi et al. (1999), the MA-phytosiderophores having high affinity for Fe3+ are secreted through the plasmalemma via anion channels involving Na+ MA symport. Blocking of anion channels in barley root plasma membrane has been shown to result in a sharp decline in secretion of MAs. Based on DNA micro-array of gene expression in rice, Negishi et al. (2002) have suggested the possible involvement of vesicles derived from endoplasmic reticulum in secretion of phytosiderophores under conditions of iron- deficiency. Microbial siderophores in the rhizosphere are also reported to contribute to Fe3+ mobilization by plants, particularly when iron supply is limiting (Zhang et al. 1991c Masalha et al. 2000). Evidence based on physiological characterization of the maize mutant YS1 suggests that Fe3+ -...

Phytoextraction Vs Phytostabilization

Alternatives to phytoremediation include ex situ washing methods with strong chelating agents such as EDTA 124 or acids 125 . Attempts to use the same chemicals in situ to enhance metal uptake into plants have had limited success 126 , are often prohibitively expensive, and may be destructive to fertility and soil biota also, residual concentrations in soil pore water may pose a risk of ground water contamination. Nevertheless, BCFs can vary by an order of magnitude over a relatively short pH range from 5.5 to 7.0 in leaf and root vegetables 127 , and Cd uptake into Salix has been found to be highly pH dependent in field stands 90 . It may be possible to enhance Cd uptake with low-cost organic or inorganic acid soil amendments.

Physiology and ecophysiology

Cymbopogon flexuosus (also known as lemongrass) is a perennial, multicut aromatic grass that yields an essential oil used in perfumery and pharmaceutical industries and vitamin A. It has a long initial lag phase. The growth and herbage and oil production of C. flexuosus in response to different levels of irrigation water (IW) 0.1, 0.3, 0.5, 0.7, 0.9, 1.1, 1.3, and 1.5 times cumulative pan evaporation CPE evaluated on deep sandy soils showed that an increment in the level of irrigation increased the plant height up to 0.7 IW CPE ratio. However, the response of irrigation levels on tiller production of lemongrass differed with the season of harvest. Oil content had an inverse relationship with the levels of irrigation, whereas significantly higher herb and essential oil yields were recorded at 0.7 IW CPE ratio, irrespective of season of harvest (Singh et al. 2000). Application of nitrogen (0, 50, 100, and 150 kg N ha-1 yr-1) and phosphorus to C. flexuosus crops maintained the fertility...

Localization of Heavy Metals in Cells and Tissues of Different Plant Organs

Rejective Way Silicon Uptake

Like cell walls or trichome, and the chelation of the metals by a ligand in cytoplasm, followed by the sequestration of the metal ligand complex into the vacuole, in the different organs such as roots, stems and leaves (Yang et al. 2005). Generally, the heavy metal contents in plant organs decrease in the following sequence root leaves stems inflorescence seeds. However, this order sometimes varies with plant species, especially in hyperaccumulators, of which the shoots have the highest heavy metal content. Roots usually manifest the maximum content of heavy metals. Leaves vary with age in their ability to accumulate heavy metals, some heavy metals accumulate preferentially in the youngest leaves of plants, whereas in others, the maximum content is found in senescing leaves. Preventing Cd ions from entering the cytosol by the plant cell walls theoretically represents the best detoxification mechanism (Ma et al. 2005). Cd stress may be alleviated by sequestration of Cd in the cell wall...

Ferritin Overexpression In Transgenic Plants And Its Consequences

Our knowledge of the role that ferritins play in plant physiology is still very limited. Their functions have been recently addressed by an approach based on their over-expression in transgenic plants, either in the plastids (their natural cytological localization) or in the cytoplasm, to evaluate the consequences of such a deregulation on plant development and physiology (Deak et al., 1999 Goto et al., 1999 Van Wuytswinkel et al., 1999). An illegitimate ferritin accumulation was obtained in leaves and in seeds. Although no major phenotypic alterations were reported to occur in these transgenic plants, in tobacco leaves grown in vitro on a media containing 25 M Fe(III)-EDTA yellow zones were observed, consistent with a 20 decrease in chlorophyll concentration. Indeed, in these plants, some chloroplasts had an altered sub-structure with diffused thylakoids, and large stromal areas with very weak electron density (Briat et al., 1999).

Strategies For Enhanced Uptake Of Trace Elements To Facilitate Phytoextraction

This strategy of phytoextraction is based on the fact that the application of metal chelates to the soil significantly enhances metal accumulation by plants. The literature to date reports a number of chelates that have been used for chelate-induced hyperaccumulation. These include EDTA, CDTA (irans-1,2-diaminocyclohexane-N,N,N ',N'-tetraacetic acid), DTPA (diethylene triaminepentaacetic acid), EGTA ethyleneglycol-bis(P-aminoethyl ether),N,N,N',N-tetraacetic acid , EDDHA ethyl-enediaminedi (o-hydroxyphenylacetic acid) , HEDTA (N-hydroxyethyl enediaminetriacetic acid), HEIDA N-(2-hydroxyethyl)iminodiacetic acid , and NTA (nitrilo-triacetic acid) 101 . For chemically enhanced phytoextraction, establishment of a high biomass crop is required before chelate application. Brassica sp. are to be directly related to the affinity of the applied chelate for the metal 105 . Therefore, it can be concluded that, for efficient phytoextraction to occur, synthetic chelates having a high affinity for...

Organic Acids Nicotianamine Amino Acids and Phytates

Nicotianamine (NA), a non-proteinaceous amino acid synthesized in all plants by the condensation of three S-adenosyl-methionine molecules through the activity of the enzyme nicotianamine synthase (NAS), is ubiquitously present in higher plants (Fig. 1). It is known to be involved in chelation of metals such as Fe, Cu, Zn for their enhanced extraction by roots and or transport to shoost, especially under mineral-deficient conditions (Takahasi et al. 2003 Mari et al. 2006). However, recent evidence supports their possible functions in heavy metal-tolerance and hyperaccumulation in plants. The hyperaccumulation of Zn and Cd is a constitutive property of the metallophyte A. halerii. Recently, Weber et al. (2004) have used Arabidopsis gene chips to identify those genes that are more active in roots of A. halleri than A. thaliana under controlled conditions. Two genes showing highest levels of expression in A. halleri roots code for a NAS and a putative Zn2+ uptake system. In addition,...

Metal Tolerant Plants And Chelators Might Promote Phytoremediation Technology

Use of soil amendments such as synthetics (ammonium thiocyanate) and natural zeolites has yielded promising results 62-66 . EDTA, NTA, citrate, oxalate, malate, succinate, tartrate, phthalate, salicylate, acetate, etc. have been used as chelators for rapid mobility and uptake of metals from contaminated soils by plants. Use of synthetic chelators significantly increased Pb and Cd uptake and translocation from roots to shoots, facilitating phytoextraction of the metals from low-grade ores. Synthetic cross-linked polyacrylates, hydrogels have protected plant roots from heavy metal toxicity and prevented the entry of toxic metals into roots. Application of low-cost synthetics and natural zeolites on a large scale are applied to the soil through irrigation at specific stages of plant growth this might be beneficial to accelerate metal accumulation 67 . FIGURE 25.11 Citric acid is a naturally occurring chelating agent. The chelation process is water activated. EDTA, NTA, citrate, oxalate,...

Heavy Metals in Different Environmental Matrices

Rhizofiltration by symbiotic fungi and bacteria associated with the root system and the exudation of chelating agents into the rhizosphere, i.e. hydrocarbons, organic acids, amino acids and glycoproteins, are the first mechanisms of heavy metal avoidance (Marchner et al. 1996). In the root apoplast, heavy metal transport up to aerial plant organs is restricted due to their binding with carboxyl groups of galacturonic and glucuronic acids present in the structure of the cell wall. Simultaneously, root endodermis prevents radial transport of heavy metals into vascular tissue and further to upper parts of the plant. Among heavy metals, lead is a hardly mobile element, and 70-95 of its content in plants is associated within roots (Piechalak et al. 2002). Heavy metals transported through vascular tissue to upper plant parts accumulate in leaves. However, atmospheric deposition of particulate matter - taken up through stomata or adsorbed by epicuticular wax - is a significant source of...

Ethanolsoluble Extracts Of Aloe Barbadensis Miller

Factors influencing hemagglutination. ii pH, temperature, trypsin, EDTA The aloe extract was heat and trypsin resistant (but using bovine pancreatic type I protease) and pH sensitive. Acid treatment (pH 3) of the aloe extract caused a decrease of the hemagglutination activity, whereas high pH (12) treatment did not change the activity. The addition of EDTA to hemagglutination assay caused a decrease of the hemagglutination activity, indicating that Ca2+ is required for the hemagglutination.

Tetrapyrrole Biosynthesis

Mrna Biosynthesis Plants

The light-induced expression of Lhc proteins was found to coincide with the greening and maturation process of chloroplasts implying the action of a plastid signal. One potential signal could be attributed to the chlorophyll precursor Mg-Proto-Porphyrin-IX (Mg-Proto-IX). Feeding experiments with the iron chelator dipyridyl led to decreased Lhcb mRNA levels in Chlamydomonas reinhardtii (Johanningmeier and Howell 1984). The chelation of iron leads to an interruption of the heme feedback inhibition in the tetrapyrrole pathway which in turn causes accumulation of Mg-Proto-IX. This effect could be also observed in higher plants (Kittsteiner et al. 1991). Direct feeding of Mg-Proto-IX to Chlamydomonas cell cultures led to induction of nuclear heat-shock genes HSP70a b c (Kropat et al. 1997) supporting the notion that this chlorophyll precursor could mediate a retrograde signal which affects nuclear gene expression. The phenotype of the gun mutants varies from pale yellowish to...

Conclusions

It is generally accepted that the rhizosphere plays an important role in the bioavailability of trace elements. A range of mechanisms exists, such as excretion of H+ or HCO3- respiration and release of CO2 exudation desorption and adsorption of trace elements dissolution-precipitation redox reaction and chelation, by which plant roots can modify the chemical conditions in the rhizosphere. These factors can affect dramatically the behavior of root in the rhizosphere and substantially the bioavailability of trace elements. The mechanisms involved in chemical modifications in the rhizo-sphere as well as on uptake of trace elements differ among plant species and soil conditions.

Hemicelluloses

These are not extracted by chelating agents or ice-cold Na2CO3, but are by concentrated aqueous alkali. They generally share the property of hydrogen-bonding to cellulose, at least in vitro and some hemicelluloses probably also do this in muro, tethering adjacent microfibrils (Fry 1989 Hayashi 1989) . For this reason, the term 'crosslinking glycans' was suggested for hemicelluloses. However, this term is not used here because the proposed in-muro tethering role remains largely hypothetical in many cases, and also because some non-hemicellulosic polysaccharides (e.g. rhamnogalacturonan II, RG-II) do crosslink.

Calculations

Step 1 Calculate the amount of a phenolic compound (APhc) extracted with neutral EDTA, considering concentration of phenolic compound (Cphc) determined after HPLC analysis and total volume of methanol fraction (Vm6oh) Step 2 Express content of a phenolic compound extracted with EDTA (Cedta) per g of dry soil CEDTA APhc ( mol) dry weight (g) For example, if Aphc is 100 mol and dry weight is 20 g, then Step 3 Calculate reversibly bound phenolic acids weakly sorbed on soil particles (Crb), subtracting the amount of phenolic compounds extracted with water (Cw) from that extracted with EDTA (Cedta) Crb ( mol g) cedta ( mol g) - Cw famol g)

Pectins

Much useful work on pectin characterization can be performed on whole isolated cell walls or alcohol-insoluble residue (AlR) (see Section 1.6). However, if necessary, pectins can be extracted from some tissues (especially ripe fruits) with chelating agents at neutral pH and 20 C. This does not apply to most other plant tissues, especially actively growing ones. Extraction can be increased by heating, but with partial depolymerization. Heating at around pH4 is least detrimental in this respect at this pH, oxalate is a more effective chelator than EDTA or EGTA. Oxalate is also easier than EDTA, EGTA and hexametaphosphate to remove (e.g. by dialysis) after pectin extraction. Another agent increasing some pectins' extractability,

Treatment

Therapy immunotherapy and several alternative and complementary therapies including nutritional therapy, chelation, and vitamin and other nutritional supplementation. The following sections describe a number of treatments investigated for autism, and their effects. Chelation

Figure

In test tubes (i.e., closed system unpublished data) containing 1 g air-dried autoclaved Cecil Ap - horizon soil (pH 5.0), 82 pg p-coumaric acid, Hoagland's solution (all solutions adjusted to pH 5.0), and soil extract for inoculum (total of 1.5 ml) the average linear transformation rates for p-coumaric acid over 48 hr, once microbial utilization was evident, were 3.6 x 10-4 + 1.7 x 10-4 picomole CFU of p-coumaric acid utilizing bacteria h, about 130 times slower than what was observed for the mean utilization in the steady-state continuous flow system. The CFU of p-coumaric acid utilizing bacteria g soil in the test tube system averaged 1.46 x 108 over the 48 h interval. Initial CFU of p-coumaric acid utilizing bacterial populations g soil 24 hr after addition of inoculum were 105 + 15. Utilization of p-coumaric acid by microbes in the test tubes was determined by 0.25 M EDTA (pH 7.0) extractions at 6 h intervals and HPLC analyses.2 CFU for bacteria that utilized p-coumaric acid as a...