Organic ligands, such as EDTA, accelerate the dissolution of silicate and oxide minerals. In natural systems, oxyanions can compete with organic ligands for mineral surface sites thereby affecting ligand-promoted dissolution rates, either enhancing or inhibiting dissolution, depending upon pH. The influence of selenite, molybdate and phosphate on the EDTA-promoted dissolution of goethite has been examined and a mechanism proposed for the observed differences in dissolution rates over a pH range of 4–8. We propose that the surface complex formed by EDTA is the controlling factor for the observed dissolution rate, with mononuclear complexes accelerating dissolution compared to bi- or multinuclear complexes. Dissolution results from our experiments suggest that EDTA forms multinuclear complexes at pH values ⩾6 and mononuclear complexes at pH values <6. Dissolution results show that when the oxyanion and the EDTA are present in the system at concentrations nearly equalling the surface sites available for adsorption, the oxyanion reduces the adsorption of EDTA and inhibits dissolution. However, if the oxyanion is present at lower concentrations at pH values ⩾6, EDTA is adsorbed but the number of carboxylic groups that can bind to the surface is reduced causing the formation of mononuclear complexes. This shift to a weaker surface complex enhances the EDTA-promoted dissolution of goethite in the presence of the oxyanions compared to EDTA-promoted dissolution in their absence.

The structural details of chromosomes have been of interest to researchers for many years, but how the metaphase chromosome is constructed remains unsolved. Divalent cations have been suggested to be required for the organization of chromosomes. However, detailed information about the role of these cations in chromosome organization is still limited. In the current study, we investigated the effects of Ca2+ and Mg2+ depletion and the reversibility upon re-addition of one of the two ions. Human chromosomes were treated with different concentrations of Ca2+and Mg2+. Depletion of Ca2+ and both Ca2+ and Mg2+ were carried out using 1, 2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid and ethylenediaminetetraacetic acid (EDTA), respectively. Chromosome structure was examined by fluorescence microscopy and scanning electron microscopy. The results indicated that chromosome structures after treatment with a buffer without Mg2+, after Ca2+ depletion, as well as after depletion of both Mg2+, and Ca2+, yielded fewer compact structures with fibrous chromatin than those without cation depletion. Interestingly, the chromatin of EDTA-treated chromosomes reversed to their original granular diameters after re-addition of either Mg2+ or Ca2+ only. These findings signify the importance of divalent cations on the chromosome structure and suggest the interchangeable role of Ca2+ and Mg2+.

In the UK, technetium may be disposed of in a high pH, low Eh cementitious repository. In such a scenario, its chemistry would be dominated by TcO4 −, in aerobic conditions and the sparingly soluble TcO2(s) in anaerobic conditions. Repository heterogeneity could mean that both Tc(VII) and Tc(IV) are present simultaneously. The anthropogenic ligands EDTA and picolinic acid are commonly used as decontamination agents and are likely to be present in intermediate-level waste (ILW). They could complex with Tc(IV) increasing its aqueous concentration and mobility in the cement porewaters and beyond. The conditional stability constants (measured in 0.3 mol dm−3 NaOH) for the Tc(IV)–EDTA and Tc(IV)–picolinic acid complexes have been determined to be: βTc(IV)−EDTA = 1.6 × 1026, which corresponds to log β = 25.2±0.6; and βTc(IV)−PA = 8.65 × 1026, which corresponds to log β = 26.9±0.1, respectively.

Ternary systems of 152Eu(III), bulk bentonite and ethylenediaminetetraacetic acid (EDTA) ([Eu] = 7.9 × 10–10 M; pH = 6.0–7.0) have been studied. Without EDTA, there was slow uptake in a two-stage process, with initial rapid sorption of Eu(III) (96%), followed by slower uptake of a much smaller fraction (3.0% over a period of one month). The reversibility of Eu(III) binding was tested by allowing Eu(III) to sorb to bentonite for 1–322 days. EDTA was added to the pre-equilibrated Eu bentonite systems at 0.01 M, a concentration that was sufficient to suppress sorption in a system where EDTA was present prior to the contact of Eu(III) with bentonite. A fraction of the Eu was released instantaneously (30–50%), but a significant amount remained bound. With time, the amount of Eu(III) retained by the bentonite reduced, with a slow fraction dissociation rate constant of approximately 4.3 × 10–8 s–1 (values in the range 2.2 × 10–8 – 1.0 × 10–7 s–1) for pre-equilibration times ≥7 days. Eventually, the amount of Eu(III) remaining bound to the bentonite was within error of that when EDTA was present prior to contact (4.5% ± 0.6), although in systems with pre-equilibration times >100 days, full release took up to 500 days. Europium interactions with colloidal bentonite were also studied, and the dissociation rate constant measured by a resin competition method. For the colloids, more Eu was found in the slowly dissociating fraction (60–70%), but the first-order dissociation rate constant was faster, with an average rate constant of 8.8 × 10–7 s–1 and a range of 7.7 × 10–7 –9.5 × 10–7 s–1. For both bulk and colloidal bentonite, although slow dissociation was observed for Eu(III), there was no convincing evidence for 'irreversible' binding.

The effect of various growth regulators on seedling field bindweed (Convolvulus arvensis L. # CONAR) growth and control with herbicides was evaluated. Fourteen growth regulators were applied at 0.38 to 380 g/ha 7 days before herbicide application in greenhouse, growth chamber and field studies. Field bindweed seedlings pretreated with growth regulators were more effectively controlled by herbicides compared to those not pretreated in greenhouse evaluations. Abscisic acid [[R-(Z,E)]-(+)-5-(1-hydroxy-2,6-6-trimethyl-4-oxo-2-cyclohexane-1-yl)-3-methyl-2,4-pentadicenoic acid] (ABA), ancymidol [a-cyclopropyl-a-(p-methoxyphenyl)-5-pyrimidine methanol], cycloheximide {3-[2-(3,5-dimethyl-2-oxocylohexyl)-2-hydroxyethyl]glutarimide}, ethylenediamine tetraacetic acid [N,N′-1,2-ethanediyl-bis-(N-(carboxymethyl) glycine] (EDTA), and 1-naphthaleneacetic acid (NAA) increased field bindweed stem length. Ancymidol and gibberellic acid [ent-3α,10,13-trihydroxy-20-norgibberell-1,16-diene-7,19-dioc acid 19,10-lactone] (GA) increased root weight, and GA increased root length. Cycloheximide, ethephon [(2-chloroethyl)phosphonic acid] and MH (1,2-dihydro-3,6-pyridazinedione) decreased field bindweed root weight. Ancymidol, GA and IAA (indole-3-acetic acid) increased the number of shoots per plant of seedling field bindweed. Dicamba (3,6-dichloro-2-methoxybenzoic acid) efficacy was enhanced following field bindweed preconditioning with ethephon and IAA. Ancymidol and cycloheximide applied as pretreatments increased glyphosate [N-(phosphonomethyl)glycine] activity on seedling field bindweed. Ancymidol and IAA pretreatment improved field bindweed control with triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid}. Herbicide-growth regulator combination treatments that increased field bindweed control in greenhouse and growth chamber studies did not increase top growth control in the field.

The aim of the present work was to assess the characteristics of the paracasein of two ewe's milk cheese varieties using various concentrations of urea and EDTA to solubilise caseins and calcium. The solubilised paracasein elements were evaluated by means of RP-HPLC and AAS. For this purpose cheeses with different physical and biochemical characteristics, i.e. Feta (53·1% moisture and pH 4·32) and Graviera Kritis (33·2% moisture and pH 5·54) were analysed. Soluble calcium of Feta was 71% of total calcium much higher than the 25% in Graviera. Treatment with 4 m urea fully solubilised Feta paracasein, whereas 6 m urea was needed to solubilise caseins from Graviera. Caseins were released from both cheeses by 100 mm EDTA. Solubilisation of paracasein induced by urea or EDTA was not significantly affected (P < 0·05) by the type of cheese. Similarly to urea, EDTA induced significantly (P < 0·05) lower solubilisation of αs1-casein in Graviera than in Feta, based on αs1-cn/β-cn ratio. A great part of calcium in both cheeses was solubilised by 50 mm EDTA while the release of casein was poor, confirming the important role of types of interactions other than protein-calcium bonds in the paracasein network. Hydrophobic interactions, hydrogen bonds and electrostatic attractions, contributed substantially to the paracasein stability of both cheese types. The interactions of αs1-casein with calcium played a more significant role in Graviera cheese than in Feta. Finally, the present study demonstrated that the profile of bonds and interactions within the cheese paracasein network was dynamicly configured by the conditions of cheese manufacture.

The aim of this study was to evaluate the efficacy of smear layer removal from teeth following root canals using lasers (Er:YAG and Nd:YAG), NaOCl, 17% EDTA, and MTAD by scanning electron microscopy (SEM). Root canals were irrigated with 3 mL of 5.25% NaOCl after each file. Teeth were randomly divided into five groups. In the final irrigation, canals were irrigated with 5.25% NaOCl (Group 1, control), 17% EDTA (Group 2), or BioPure MTAD (Group 3). Laser groups were irradiated with Er:YAG laser (1.8 W, 120 mJ, 15 Hz) (Group 4) or Nd:YAG laser (1 W, 100 mJ, 15 Hz) (Group 5). The smear layer at the apical, middle, and coronal thirds of each root canal was imaged using SEM. Smear layer removal by EDTA was the most effective in all regions. The difference between EDTA and MTAD was statistically significant in the coronal and middle (p < 0.05), but not the apical (p > 0.05), regions. The difference between the control and laser groups was not statistically significant (p > 0.05). In all regions, the difference between 17% EDTA–MTAD and the control–laser groups was statistically significant (p < 0.05). Although improvement was observed in removal of the smear layer using alternative materials and techniques, application of a combination of EDTA and NaOCl remains an effective technique.

In the absence of exogenous divalent cations, the isolated brush-border plasma membrane of Hymenolepis diminuta possesses alkaline phosphatase activity (APA). APA is stimulated in the presence of exogenous Mg2+ and inhibited by low concentrations of Zn2+ or high concentrations of Ca2+, and inhibition of APA by Zn2+ is reversed by both Mg2+ and Ca2+. APA is inhibited by ethylenediamine tetraacetic acid (EDTA), ethyleneglycol-bis-(β-aminoethyl ether) N, N′-tetraacetic acid, and 1, 10-phenanthroline in time- and concentration-dependent fashions, with EDTA being the most effective inhibitor. Following treatment with EDTA, APA is restored by Mg2+ and, to a lesser extent, by Ca2+, but not by Zn2+. Thus, APA represents a Mg2+-dependent enzyme that can be partly activated by Ca2+ but only in the absence of Mg2+.

Hypoxanthine can block preimplantation mouse embryo development in vitro at the 2- to 4-cell stages, and this has recently been shown to be reversed by cAMP-elevating agents. However, the extent of this hypoxanthine-induced arrest is determined by the culture conditions and strain of mouse. Whitten's and KSOM/AA are two embryo culture media that support preimplantation development to the blastocyst stage. This study was undertaken to examine the influence of several components in these media on hypoxanthine-arrested preimplantation mouse embryos and to test the hypothesis that reversal of the hypoxanthine block by cAMP-elevating agents requires cooperative interaction with the chelator, EDTA. Initial experiments demonstrated that embryo development was blocked in the presence of hypoxanthine in Whitten's medium but not in KSOM/AA; furthermore, removal of EDTA from KSOM/AA rendered this medium incapable of supporting high levels of development to blastocyst (9%), whereas high numbers of blastocysts (80%) formed in Whitten's medium, which does not contain the chelator. Consequently, Whitten's medium was used to test our hypothesis. It has previously been demonstrated that the phosphodiesterase inhibitor, IBMX, can reverse the developmental arrest imposed by hypoxanthine in EDTA-supplemented Earle's basic salt solution, but in the present study the addition of IBMX to Whitten's medium resulted in a block to development and failed to reverse the hypoxanthine arrest. These disparate effects can be explained by the presence or absence of EDTA. Supplementing Whitten's medium with EDTA reverses the IBMX effect, but not the hypoxanthine-induced block. While IBMX alone is unable to reverse the hypoxanthine block in Whitten's medium, development is greatly enhanced by the simultaneous addition of EDTA and IBMX. Similar results were obtained with the cAMP analogue, 8-AHA-cAMP. The data therefore support our hypothesis that the reversal of the hypoxanthine-induced arrest by cAMP-elevating agents is critically dependent on the presence of EDTA. We contrast this with the situation in mouse oocytes, where the hypoxanthine-induced meiotic arrest is not reversed by the addition of EDTA and/or cAMP-elevating agents.

The effectiveness of EDTA compounds on iron fortificants for potential use in Egyptian balady bread was tested in sixty SpragueDawley weanling male rats by the haemoglobin regeneration efficiency (HRE) method. To confirm HRE-derived findings, eight groups of ten animals were repleted with a modified American Institute of Nutrition (1977; AIN) 76A diet, fortified with ferric phosphate, electrolytic Fe, carbonyl Fe or ferrous sulphate, with and without ascorbic acid. Results without ascorbic acid were comparable to findings of a human study by Forbes et al. (1989). Bioavailability of EDTA-enhanced fortificants, FeSO4 + Na2EDTA and NaFe(III)EDTA, was compared with that of FeSO4 in six groups of ten animals repleted with a ground Egyptian bread meal or a casein-based AIN diet fortified with one of the three compounds. Addition of either EDTA compound significantly increased bioavailability of Fe in Egyptian balady bread. When present in the less inhibitory casein meal, however, FeSO4 + Na2EDTA fortification was significantly less effective than NaFe(1II)EDTA or the reference FeSO4. Results indicate that NaFe(I1I)EDTA may be the fortificant of choice in a mixed diet. Further study of EDTA- enhanced Fe fortificants is needed.