Hydrolysis of nitriles using an immobilized nitrilase: applications to the synthesis of methionine hydroxy analogue derivatives

Mild and selective hydrolysis of a large range of nitriles leading to carboxylic acids was achieved under neutral conditions by an immobilized and genetically modified enzyme preparation from Alcaligenes faecalis ATCC8750. This immobilized nitrilase has been shown to be an effective catalyst for the stereoselective hydrolysis of mandelonitrile 1a to R-(-)-mandelic acid 1c. This method is particularly useful for the production of hydroxy analogues of methionine derivatives 2c-4c that could have an interest in cattle feeding and for the transformation of compounds containing other acid- or base-sensitive groups 3a-10a. A series of aliphatic dinitriles 11a-15a was hydrolyzed to the corresponding cyano acids. The suitability of the immobilized catalyst as a robust and versatile biocatalyst is discussed, and models to account for the stereoselectivity of the enzymic hydrolysis have been proposed.     

Cloning, expression, and characterization of a D-psicose 3-epimerase from Clostridium cellulolyticum H10

The noncharacterized protein ACL75304 encoded by the gene Ccel_0941 from Clostridium cellulolyticum H10 (ATCC 35319), previously proposed as the xylose isomerase domain protein TIM barrel, was cloned and expressed in Escherichia coli . The expressed enzyme was purified by nickel-affinity chromatography with electrophoretic homogeneity and then characterized as d-psicose 3-epimerase. The enzyme was strictly metal-dependent and showed a maximal activity in the presence of Co(2+). The optimum pH and temperature for enzyme activity were 55 °C and pH 8.0. The half-lives for the enzyme at 60 °C were 6.8 h and 10 min when incubated with and without Co(2+), respectively, suggesting that this enzyme was extremely thermostable in the presence of Co(2+) but readily inactivated without metal ion. The Michaelis-Menten constant (K(m)), turnover number (k(cat)), and catalytic efficiency (k(cat)/K(m)) values of the enzyme for substrate d-psicose were estimated to be 17.4 mM, 3243.4 min(-1), and 186.4 mM min(-1), respectively. The enzyme carried out the epimerization of d-fructose to d-psicose with a conversion yield of 32% under optimal conditions, suggesting that the enzyme is a potential d-psicose producer.     

Computer simulation of the interactions of glyphosate with metal ions in phloem

Essential nutrients such as trace metal ions, amino acids, and sugars are transported in the phloem from leaves to other parts of the plant. The major chelating agents in phloem include nicotianamine, histidine, cysteine, glutamic acid, and citrate. A computer model for the speciation of metal ions in phloem has been used to assess the degree to which the widely used herbicide glyphosate binds to Fe(3+), Fe(2+), Cu(2+), Zn(2+), Mn(2+), Ca(2+), and Mg(2+) in this fluid over the pH range of 8 to 6.5. The calculations show that glyphosate is largely unable to compete effectively with the biological chelating agents in phloem. At a typical phloem pH of 8, 1.5 mM glyphosate binds 8.4% of the total Fe(3+), 3.4% of the total Mn(2+), and 2.3% of the total Mg(2+) but has almost no effect on the speciation of Ca(2+), Cu(2+), Zn(2+), and Fe(2+). As the pH decreases to 6.5, there are some major shifts of the metal ions among the biological chelators, but only modest increases in glyphosate binding to 6% for Fe(2+) and 2% for Zn(2+). The calculations also indicate that over 90% of the glyphosate in phloem is not bound to any metal ion and that none of the metal-glyphosate complexes exceed their solubility limits.     

Fourier transform near-infrared spectroscopy application for sea salt quality evaluation

Near-infrared (NIR) spectroscopy in diffuse reflectance mode was explored with the objective of discriminating sea salts according to their quality type (traditional salt vs "flower of salt") and geographical origin (Atlantic vs Mediterranean). Sea salts were also analyzed in terms of Ca(2+), Mg(2+), K(+), alkalinity, and sulfate concentrations to support spectroscopic results. High concentrations of Mg(2+) and K(+) characterized Atlantic samples, while a high Ca(2+) content was observed in traditional sea salts. A partial least-squares discriminant analysis model considering the 8500-7500 cm(-1) region permitted the discrimination of salts by quality types. The regions 4650-4350 and 5900-5500 cm(-1) allowed salts classification according to their geographical origin. It was possible to classify correctly 85.3 and 94.8% of the analyzed samples according to the salt type and to the geographical origin, respectively. These results demonstrated that NIR spectroscopy is a suitable and very efficient tool for sea salt quality evaluation.     

Purification and characterization of ferulic acid esterase from malted finger millet (Eleusine coracana, Indaf-15)

Ferulic acid esterase (EC 3.1.1.73) cleaves the feruloyl groups substituted at the 5'-OH group of arabinosyl residues of arabinoxylans and is known to modulate their functional properties. In this study, ferulic acid esterase from 96 h finger millet malt was purified to apparent homogeneity by three-step purification with a recovery of 3% and a fold purification of 22. The substrate p-nitrophenylferulate (PNPF) was synthesized and used to assay this enzyme spectrophotometrically. The products liberated from ragi and wheat water-soluble polysaccharides by the action of purified ragi ferulic acid esterase were identified by ESI-MS. The pH and temperature optima of the enzyme were found to be 6.0 and 45 degrees C, respectively. The pH and temperature stabilities of the enzyme were found to be in the range of 5.5-9.0 and 30 degrees C, respectively. The activation energy of the enzymatic reaction was found to be 4.08 kJ mol(-1). The apparent K m and V max of the purified ferulic acid esterase for PNPF were 0.053 microM and 0.085 unit mL(-1), respectively. The enzyme is a monomer with a molecular mass of 16.5 kDa. Metal ions such as Ni(2+), Zn(2+), Co(2+), and Cu(2+) and oxalic and citric acids enhanced the enzyme activity. The enzyme was completely inhibited by Fe(3+). Group specific reagents such as p-chloromercuric benzoate and iodoacetamide inhibited the enzyme, indicating the possible presence of cysteine residues in the active site pocket.     

Production, purification, and properties of an endoglucanase produced by the hyphomycete Chalara (Syn. Thielaviopsis) paradoxa CH32

The hyphomycete Chalara (syn. Thielaviopsis) paradoxa produces endoglucanase activity during the late trophophase. The low molecular mass (35 kDa) endoglucanase purified from cultured broths works optimally at 37 degrees C and pH 5.0. The enzyme inactivates at pH below 3.0 and also at temperatures of 50 degrees C or higher, but it is stable at lower temperatures, including refrigeration temperature and freezing. The enzyme is inhibited by detergents, by EDTA, and by the divalent cations Hg(2+) and Ag(2+). It is also inhibited to some extent by 10 mM Zn(2+), Fe(2+), and Mg(2+), but it is stimulated by Mn(2+). Enzyme activity is not affected by reducing agents. In the presence of low concentrations of water miscible organic solvents (20%) endoglucanase activity is inhibited by 7% (for methanol) to 50% (for acetonitrile), and it is totally inhibited at higher solvent concentrations (50%). Enzyme activity is not affected by the water immiscible solvent ethyl acetate. Carboxymethylcellulose is the preferred substrate (K(m(app)) = 8.3 g/L; V(max(app)) = 1.1 microM/min). Hydrolysis of crystalline cellulosic substrates is very limited, but it is greatly enhanced by phosphoric acid swelling. The purified enzyme shows no activity toward disaccharides or aryl-glucosides. Its activity is inhibited by cellobiose.     

棕壤及其各粒级微团聚体对Cu~(2+)吸附解吸特性的研究

采用室内分析的方法,研究了棕壤及其各粒级微团聚体对Cu2+的吸附解吸作用。结果表明:棕壤与其各粒级微团聚体相比,对Cu2+的吸附能力较弱,而三级微团聚体对Cu2+的吸附能力的大小顺序为:<10μm粒级微团聚体>10~50μm粒级微团聚体>50~250μm粒级微团聚体。同时,通过NH4OAc,EDTA对Cu2+的解吸情况的研究得出,棕壤及其不同粒级微团聚体对Cu2+的吸附机制是不同的,在棕壤和各粒级微团聚体中,<10μm粒级的微团聚体对Cu2+的吸附机制以专性吸附为主,固定Cu2+的能力最强,从而能降低Cu2+的活性,不易为植物吸收,其次为10~50μm粒级微团聚体和棕壤,而50~250μm粒级微团聚体对Cu2+的吸附以静电吸附机制为主,其吸附的Cu2+可以被交换,因此固定Cu2+的能力较差。     

Highly effective adsorption of heavy metal ions from aqueous solutions by macroporous xylan-rich hemicelluloses-based hydrogel

Xylan-rich hemicelluloses-based hydrogel was developed as a novel porous bioadsorbent by graft co-polymerization of acrylic acid (AA) and xylan-rich hemicelluloses for adsorption of heavy metal ions (Pd(2+), Cd(2+), and Zn(2+)) from aqueous solutions. The chemical structure, the interaction between the hydrogel and metal ions, and the porous structure of xylan-rich hemicelluloses-g-AA hydrogel were revealed by Fourier transform infrared spectroscopy and scanning electron microscopy. The effects of AA and cross-linker dosage, pH value, contacting time, and initial concentration of metal ion on the adsorption capacity were studied. The adsorption equilibrium time was about 60 min from the adsorption kinetics study. The maximum adsorption capacities of Pd(2+), Cd(2+), and Zn(2+) were 859, 495, and 274 mg/g, respectively. Furthermore, xylan-rich hemicelluloses-g-AA hydrogel also exhibited highly efficient regeneration and metal ion recovery efficiency and can be reused without noticeable loss of adsorption capacity for Pd(2+), Cd(2+), and Zn(2+) after quite a number of repeated adsorption/desorption cycles.     

Sequestering Ability of Phytate toward Biologically and Environmentally Relevant Trivalent Metal Cations

Quantitative parameters for the interactions between phytate (Phy) and Al(3+), Fe(3+), and Cr(3+) were determined potentiometrically in NaNO(3) aqueous solutions at I = 0.10 mol L(-1) and T = 298.15 K. Different complex species were found in a wide pH range. The various species are partially protonated, depending on the pH in which they are formed, and are indicated with the general formula MH(q)Phy (with 0 ≤ q ≤ 6). In all cases, the stability of the FeH(q)Phy species is several log K units higher than that of the analogous AlH(q)Phy and CrH(q)Phy species. For example, for the MH(2)Phy species, the stability trend is log K(2) = 15.81, 20.61, and 16.70 for Al(3+), Fe(3+), and Cr(3+), respectively. The sequestering ability of phytate toward the considered metal cations was evaluated by calculating the pL(0.5) values (i.e., the total ligand concentration necessary to bind 50% of the cation present in trace in solution) at different pH values. In general, phytate results in a quite good sequestering agent toward all three cations in the whole investigated pH range, but the order of pL(0.5) depends on it. For example, at pH 5.0 it is pL(0.5) = 5.33, 5.44, and 5.75 for Fe(3+), Cr(3+), and Al(3+), respectively (Fe(3+) < Cr(3+) < Al(3+)); at pH 7.4 it is pL(0.5) = 9.94, 9.23, and 8.71 (Al(3+) < Cr(3+) < Fe(3+)), whereas at pH 9.0 it is pL(0.5) = 10.42, 10.87, and 8.34 (Al(3+) < Fe(3+) < Cr(3+)). All of the pL(0.5) values, and therefore the sequestering ability, regularly increase with increasing pH, and the dependence of pL(0.5) on pH was modeled using some empirical equations.     

Dehydroascorbate reductase cDNA from sweet potato (Ipomoea batatas [L.] Lam): expression, enzyme properties, and kinetic studies

A cDNA encoding a putative dehydroascorbate reductase (DHAR) was cloned from sweet potato. The deduced protein showed a high level of sequence homology with DHARs from other plants (67 to approximately 81%). Functional sweet potato DHAR was overexpressed and purified. The purified enzyme showed an active monomeric form on a 12% native PAGE. The protein's half-life of deactivation at 50 degrees C was 10.1 min, and its thermal inactivation rate constant K(d) was 6.4 x 10(-2) min(-1). The enzyme was stable in a broad pH range from 6.0-11.0 and in the presence of 0.8 M imidazole. The K(m) values for DHA and GSH were 0.19 and 2.38 mM, respectively.     

不同浓度Hg2+ 、Cr3+ 和Pb2+单一胁迫对绿豆膜脂过氧化物含量及抗氧化酶活性的影响

研究了不同浓度Hg2+、Cr3+ 和Pb2+胁迫条件下,绿豆花荚期叶片中膜脂过氧化物（MDA）含量及抗氧化酶,包括(超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT))活性的变化情况。结果表明,Hg2+、Cr3+和Pb2+胁迫后,随着浓度的升高,绿豆叶片中MDA含量也逐渐升高,与对照相比均呈差异显著性;在Cr3+和Pb2+胁迫下,绿豆叶片中SOD酶活性随着浓度的升高呈现升高的趋势;在低、中浓度Hg2+胁迫下,SOD酶活性低于对照,但高浓度下,SOD酶活性高于对照;Hg2+处理后,POD随着浓度的增加,表现出先升高后降低又升高的趋势;低、中浓度Cr 3+处理使绿豆叶片内POD活性降低,但在高浓度时表现出POD活性增强;随着Pb2+处理浓度的增加,POD活性逐渐降低;Hg2+ 和Cr3+处理使CAT活性升高,但Pb2+处理后,CAT活性随浓度的升高先下降,再升高,然后又下降。研究表明Pb2+对绿豆的生态毒性较大。     

Monothiol glutaredoxin cDNA from Taiwanofungus camphorata: a novel CGFS-type glutaredoxin possessing glutathione reductase activity

Glutaredoxins (Grxs) play important roles in the redox system via reduced glutathione as a reductant. A TcmonoGrx cDNA (1039 bp, EU158772) encoding a putative monothiol Grx was cloned from Taiwanofungus camphorata (formerly named Antrodia camphorata). The deduced amino acid sequence is conserved among the reported monothiol Grxs. Two 3-D homology structures of the TcmonoGrx based on known structures of human Grx3 (pdb: 2DIY_A) and Mus musculus Grx3 (pdb: 1WIK_A) have been created. To characterize the TcmonoGrx protein, the coding region was subcloned into an expression vector pET-20b(+) and transformed into E. coli C41(DE3). The recombinant His6-tagged TcmonoGrx was overexpressed and purified by Ni(2+)-nitrilotriacetic acid Sepharose. The purified enzyme showed a predominant band on 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme exhibited glutathione reductase (GR) activity via dithionitrobenzoate (DTNB) assay. The Michaelis constant (K(M)) values for GSSG and NADPH were 0.064 and 0.041 mM, respectively. The enzyme's half-life of deactivation at 60 °C was 10.5 min, and its thermal inactivation rate constant (k(d)) was 5.37 × 10(-2) min(-1). The enzyme was active under a broad pH range from 6 to 8. The enzyme retained 50% activity after trypsin digestion at 37 °C for 40 min. Both mutants C(40)→S(40) and C(165)→S(165) lost 40-50% GR activity, whereas the mutant S(168)→C(168) showed a 20% increase in its GR activity.     

Immobilization of recombinant invertase (re-INVB) from Zymomonas mobilis on D-sorbitol cinnamic ester for production of invert sugar

The recombinant invertase (re-INVB) from Zymomonas mobilis was immobilized by adsorption onto the totally cinnamoylated derivative of D-sorbitol. The polymerization and cross-linking of the derivative initially obtained was achieved by irradiation in the ultraviolet region, where this prepolymer shows maximum sensitivity. Immobilization of re-INVB on this support involves a process of physical adsorption and intense hydrophobic interactions between the cinnamoyl groups of the support and related groups of the enzyme. Enzyme concentration, immobilization time, and irradiation time were important parameters affecting the immobilization efficiency. The optimum reaction pH of immobilized enzyme was 5, and the optimal reaction temperature was 40 degrees C. The apparent Michaelis constant and the apparent catalytic constant of re-INVB immobilized on the SOTCN derivative acting on sucrose was 78+/-5 mM and 5x10(4)+/-3x10(2) s(-1), respectively, while for the free enzyme, it was 98.0+/-4 mM and 1.2x10(4)+/-2.5x10(2) s(-1), respectively, suggesting a better apparent affinity of the enzyme for the substrate and a better hydrolysis rate when immobilized than when in solution. Immobilized re-INVB also showed good thermal stability and good operational stability (40% of the initial activity remaining after 45 cyles of 1 min duration and 90.6 mg of sucrose being hydrolyzed in 45 min per 2.5 mg of immobilized protein). The results showed that cinnamic carbohydrate esters of D-sorbitol are an appropriate support for re-INVB immobilization and the production of invert sugar.     

Cloning, expression, and characterization of two beta-glucosidases from isoflavone glycoside-hydrolyzing Bacillus subtilis natto

On the basis of the genomic sequence of Bacillus subtilis 168, two beta-glucosidase genes (bglH and yckE) from B. subtilis natto, which has been reported to have high isoflavone glucoside-hydrolyzing activity, were cloned and overexpressed in E. coli M15. The temperature for the optimal p-nitrophenyl-beta-D-glucoside hydrolyzing activity of both enzymes was between 37 and 45 degrees C, but BglH had a higher thermal stability than YckE. Both showed high activity at pH 6.0, but YckE was stable over a wider pH range than BglH. Recombinant BglH was inhibited 73%, 63%, and 43% by 1.0 mM Cd(2+), Fe(2+), or Cu(2+), respectively, while other divalent metal ions resulted in 0-23% inhibition, whereas YckE was inhibited by less than 20% by any of the divalent metal ions we tested. Among the substrate we used, BglH showed the highest affinity for genistin and YckE showed the highest affinity for p-nitrophenyl-beta-D-fructopyranoside. Both BglH and YckE hydrolyzed genistin and daidzin into their isoflavone aglycones, genistein and daidzein, but BglH was more efficient than YckE in isoflavone glucoside hydrolysis (20-fold higher kcat). Our results suggest that recombinant BglH may be applicable in the process of isoflavones deglycosylation.     

重金属对水稻光合作用和同化物输配的影响

光合速率测定表明,0.025～1.0mmolL的Cu2+、Cd2+和Hg2+显著抑制水稻叶片的光合速率,且抑制程度随Cu2+、Cd2+和Hg2+浓度的增高而增强。示踪动力学分析表明,0.5mmolL的Cu2+、Cd2+和Hg2+抑制光合产物在叶内不同状态间的转化,影响叶中光合产物的输出,导致叶内小分子糖的累积,使叶片光合速率受糖浓度增高的反馈调节而下降。电泳分析表明,Cu2+、Cd2+和Hg2+抑制叶内淀粉酶同功酶的表达,并进而抑制光合同化物在叶内可输配态和暂贮态之间的转化。     

Recovery and characterization of the metal polymeric organic fraction (polymerin) from olive oil mill wastewaters

A dark and complex metal polymeric organic mixture, named polymerin, was recovered from olive oil mill wastewaters (OMWW) and characterized by chemical analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and atomic absorption spectrometry (AAS). Polymerin proved to be composed of carbohydrates (52.40 mg 100(-1), w/w), melanin (26.14 mg 100(-1)), and proteins (10.40 mg 100(-1)), and the respective composition of monosaccharides, phenols, and amino acids was determined. It also contained metals (11.06 mg 100(-1)), mainly K(+) and, to a lesser extent, Na(+), Ca(2+), Mg(2+), Zn(2+), Fe(3+), and Cu(2+), which were naturally bound and chelated through carboxylate anions and other characteristic nucleophilic functional groups naturally occurring in polymerin. The distribution of polymerin relative molecular size was assessed to be approximately between 500.0 and 2.0 kDa by calibrated molecular weight gel filtration chromatography, indicating also that a fraction consisted of protein, melanin, and polysaccharide, strongly aggregated to each other in a supramolecular status by a combination of covalent and hydrogen bonds and CH/Pi interactions, and another fraction of only free polysaccharide. Polymerin was transformed into a potassium salt deglycosylated derivative, named KSDpolymerin, which was also characterized by chemical analysis, DRIFTS, and AAS. KSDpolymerin consisted of carbohydrates (6.00 mg 100(-1)), melanin (52.49 mg 100(-1)), and proteins (35.40 mg 100(-1)), and the composition of monosaccharides, phenols, and amino acids was determined. It also contained metals (6.11 mg 100(-1)), mainly K(+) and to a lesser extent Na(+), Ca(2+), Mg(2+), Zn(2+) and Fe(3+), bound as in polymerin. All the organic components were strongly linked in a supramolecular aggregate status and the relative average molecular size proved to be 6.3 kDa. Finally, we briefly discuss the possible use of such polymerins in agriculture as bioamendments and macro- and microelement biointegrators and as a biofilter for toxic metal removal, in light of their similarity with humic acids.     

硫酸铈(Ce~(4+))剂量计的改进

本文采用在硫酸铈(Ce~(4+))体系中,加入硫酸铜(Cu~(2+))的方法,改进铈(Ce~(4+))剂量体系的稳定性。实验测定Ce~(4+)/Cu~(2+)体系中,Ce~(4+)的摩尔吸光度5643±451.M~(-1).cm~(-1)。在150—4×10~4Gy范围内,用三种Ce~(4+)浓度,测定水深5厘米校准点的G(Ce~(3+))为2.20±0.04。研究表明,G(Ce~(3+))值随辐照温度的上升而线性下降,测得辐照温度修正系数为-(5.13±0.07)×10~(-3)/℃。在Ce~(4+)溶液体系中,加入0.1M Cu~(2+),使剂量体系趋于稳定。对非限束~(60)Coγ源,水中校准点吸收剂量不确定度±3.3%,重复性好于±2.5%。Ce~(4+)/Cu~(2+)适宜作为辐射加工中高剂量区的参考剂量计。     

Preparation of specific monoclonal antibodies (MAbs) against heavy metals: MAbs that recognize chelated cadmium ions

Monoclonal antibodies (MAbs) were produced against chelated Cd (2+). Since Cd (2+) ions are too small to elicit an immune response, the metal was coupled to protein carrier (keyhole limpet hemocyanin, KLH) using a bifunctional chelator 1-(4-isothiocyanobenzyl)ethylenediamine N, N, N', N'-tetraacetic acid (ITCBE). Several mice were immunized with this Cd (2+)-ITCBE-KLH immunoconjugate. Spleen cells of two immunized mice were fused with myeloma cells, and the resulting hybridomas were screened using protein conjugates with covalently bound metal-free ITCBE (ethylenediamine tetraacetic acid) or Cd (2+)-ITCBE. Four hybridoma cell lines that produced MAbs with high selectivity and sensitivity (Aa4, Aa6, Ac4, and Ba2) were expanded for further study. Cross-reactivities with other metals were below 1% except for Hg (2+), which showed a slight cross-reactivity in competitive ELISA. These antibodies were used to construct competitive ELISAs for ionic cadmium; the IC 50 of the four antibodies (Aa4, Aa6, Ac4, and Ba2) were 10.59, 4.19, 29.45, and 6.63 microg/L, respectively. The detection range and the lowest detection limit for cadmium, using the Aa6 antibody, were 2.19-86.38 microg/L and 0.313 microg/L, respectively. Spike-recovery studies in tap and stream water showed that the most sensitive antibody can be used for cadmium detection in drinking water.     

Nature of impurities in fertilizers containing EDDHMA/Fe(3+), EDDHSA/Fe(3+), and EDDCHA/Fe(3+) chelates.

Iron chelates derived from ethylenediaminedi(o-hydroxyphenylacetic) acid (EDDHA), ethylenediaminedi(o-hydroxy-p-methylphenylacetic) acid (EDDHMA), ethylenediaminedi(2-hydroxy-5-sulfophenylacetic) acid (EDDHSA), and ethylenediaminedi(5-carboxy-2-hydroxyphenylacetic) acid (EDDCHA) are remarkably efficient in correcting iron chlorosis in plants growing in alkaline soils. This work reports the determination of impurities in commercial samples of fertilizers containing EDDHMA/Fe(3+), EDDHSA/Fe(3+), and EDDCHA/Fe(3+). The active components (EDDHMA/Fe(3+), EDDHSA/Fe(3+), and EDDCHA/Fe(3+)) were separated easily from other compounds present in the fertilizers by HPLC. Comparison of the retention times and the UV-visible spectra of the peaks obtained from commercial EDDHSA/Fe(3+) and EDDCHA/Fe(3+) samples with those of standard solutions showed that unreacted starting materials (p-hydroxybenzenesulfonic acid and p-hydroxybenzoic acid, respectively) were always present in the commercial products. 1D and 2D NMR experiments showed that commercial fertilizers based on EDDHMA/Fe(3+) contained impurities having structures tentatively assigned to iron chelates of two isomers of EDDHMA. These findings suggest that current production processes of iron chelates used in agriculture need to be improved.     

Influence of herbicide structure,clay acidity,and humic acid coating on acetanilide herbicide adsorption on homoionic clays

Adsorption of chloroacetanilide herbicides on homoionic montmorillonite was studied by coupling batch equilibration and FT-IR analysis. Adsorption decreased in the order metolachlor > acetochlor > alachlor > propachlor on Ca(2+)- or Mg(2+)-saturated clays and in the order metolachlor > alachlor > acetachlor > propachlor on Al(3+)- or Fe(3+)-saturated clays. FT-IR spectra showed that the carbonyl group of the herbicide molecule was involved in bonding. For the same herbicide, adsorption of alachlor, acetachlor, and metolachlor on clay followed the order Ca(2+) approximately Mg(2+) < Al(3+) < or = Fe(3+), which coincided with the increasing acidity of homoionic clays. Adsorption of propachlor, however, showed an opposite dependence, suggesting a different governing interaction. In clay and humic acid mixtures, herbicide adsorption was less than that expected from independent additive adsorption by the individual constituents, and the deviation was dependent on the clay-to-humic acid ratio, with the greatest deviation consistently occurring at a 60:40 clay-to-humic acid ratio.