Systematic characterization on electronic structures and spectra for a series of complexes, M(IDB)Cl2 (M = Mn, Fe, Co, Ni, Cu and Zn): a theoretical study

Theoretical studies on the coordination stabilities, spectra and DNA-binding trend for the series of metal-varied complexes, M(IDB)Cl₂ (M = Mn, Fe, Co, Ni, Cu and Zn; IDB = N, N -bis(2-benzimidazolylmethyl) amine), have been carried out by using the DFT/B3LYP method and PCM model. The calculated coordination stabilities (S) for these complexes present a trend of S(Ni) > S(Co) > S(Fe) > S(Cu) > S(Zn) > S(Mn). It has been estimated from the molecular orbital energies of the complexes that the DNA-binding affinities (A) of the complexes are in the order of A(Zn) < A(Mn) < A(Fe) ≈ A(Co) < A(Ni) < A(Cu). The studied results indicate that the Cu, Ni and Co complexes with large coordination stabilities present the low virtual orbitals, consequently yielding to the favorable DNA-binding affinities. The spectral properties of excitation energies and oscillator strengths for M(IDB)Cl₂ in the ultraviolet region were calculated by TD-DFT/B3LYP method.     

Synthesis, spectroscopic, and antitumor activity of metal chelates of S-methyl-N-(l-isoquinolyl)-methylendithiocarbazate

Complexes of Mn(III), Fe(III), Fe(II), Co(III), Ni(II), Cu(II), Zn(II), and Pt(II) with S-methyl-N-(l-isoquinolyl) methylendithiocarbazate (N-N-SH) were isolated and characterized by elemental analysis, conductance measurement, magnetic susceptibilities, and spectroscopic studies. On the basis of these studies, a highly distorted, high-spin, chloro-bridged, polymeric octahedral structure for [Mn(N-N-S)Cl2]; a distorted, low-spin, monomeric octahedral structure for [Fe(N-N-S)2]; a distorted, high-spin, octahedral structure for [Ni(N-N-S)2]; and a square-planar structure for [M(N-N-S)X] (M = Ni, Cu, Pt or Zn and X = Cl- or -OAc) are suggested. With Fe(III), the complex [Fe(N-N-S)2][FeCl4] was isolated while the Co(II) was oxidized to yield the Co(III) ion as [Co(N-N-S)2]2[CoCl4]. All these complexes were screened for their antitumor activity against P 388 lymphocytic leukemia test system in mice. Except for Mn(III), Fe(III), and Co(III) complexes, all were found to possess significant activity; the Cu(II) and Zn(II) complexes showed a T/C% value of 160 and 195, respectively, at their optimum dosages.     

Geochemical cycling of heavy metals in a marine coastal area: benthic flux determination from pore water profiles and in situ measurements using benthic chambers

Concentrations of the heavy metals Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn were measured in sea water, suspended matter, sediments and pore water samples collected in a coastal area of the middle Tyrrhenian Sea. Concentration factors between pore water (extracted from the first centimeter of the sediments) and the overlying sea water (taken 30 cm above the sea bed) were less than 1 for Cr, Cu and Pb, 1–10 for Cd and Ni, 10–100 for Fe and Co, 100–1000 for Mn, and 1–100 for Zn.The benthic fluxes of heavy metals at the sediment-water interface were measured directly using in situ benthic chambers and calculated using Fick's first law during two experimental periods, one in 1986 and the other in 1988. The fluxes of Cu, Ni, Pb and Zn varied significantly over time; this appeared to be related to their relatively low ( 10) concentration factors. From the benthic chamber experiments, metals with positive fluxes were in the order: Mn > Fe > Co > Cd, while those with negative fluxes were: Zn > Pb > Ni Cu. Fluxes calculated using Fick's Law were: positive – Mn > Fe > Zn (or Zn > Fe) > Ni > Co > Cd, negative fluxes Pb > Cu > Cr.Measured (benthic chamber) and calculated (Fick's first law) fluxes for Co, Cd, Mn, Pb and Fe were comparable within an order of magnitude, although less agreement was found for Cu, Ni and Zn. Removal of Ni and Zn at the sediment-water interface has been proposed to explain the fact that the measured and calculated fluxes have opposite directions for these metals.     

Mineral composition in fillets of sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata): a comparison of cultured and wild fish

The objective of this study was to determine some of the trace mineral elements in four commercial feeds commonly available in Turkey for marine culture and in fillets of cultured and wild sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata). The feeds and cultured fish were from four different fish farms operating in the same region but with four slightly different feeds. Concentrations of Iron (Fe), Zinc (Zn), Manganese (Mn), Copper (Cu), Lead (Pb), Cobalt (Co), Nickel (Ni), Chromium (Cr), and Cadmium (Cd) were analyzed in the feeds and fillets of cultured as well as wild fish. Significant differences in the mineral concentrations existed within feed groups, cultured fish groups as well as between cultured and wild fish. Fe, Zn, and Mn in the feeds, Fe, Co, and Zn in sea bass and Fe, Zn and Co in sea bream were predominant among the nine analyzed minerals. Fe, Zn, Mn, Cr, and Ni contents in the fillets of wild sea bass were significantly, (P < 0.05) lower than those of the cultured sea bass groups. Co, Cr, Pb, and Ni in the fillets of wild sea bream were also significantly (P < 0.05) lower than those of cultured sea bream groups. These differences in trace elements in the cultured and wild fish were probably related to differences in their dietary mineral concentrations.     

Computational studies of modified [Fe3S4] clusters: why iron is optimal

This work reports density functional computations of metal-substituted models of biological [Fe3S4] clusters in oxidation states [MFe2S4](+/0/-1) (M=Mn, Fe, Co, Ni, Cu, Zn, and Mo). Geometry optimization with a dielectric screening model is shown to provide a substantial improvement in structure, compared to earlier used standard procedures. The error for average Fe-S bonds decreased from 0.038A to 0.016A with this procedure. Four density functionals were compared, B3LYP, BP86, TPSS, and TPSSh. B3LYP and to a lesser extent TPSSh energies were inconsistent with experiment for the oxidized [Fe3S4]+ cluster. BP86 (and to a slightly lesser extent TPSS) was within expected theoretical and experimental uncertainties for all oxidation states, the only qualitative error being 5kJ/mol in favor of the M(S)=3/2 configuration for the [Fe3S4]+ cluster, so BP86 was used for quantitative results. Computed reorganization energies and reduction potentials point directly towards the [Fe3S4] cluster as the superior choice of electron carrier, with the [ZnFe2S4] cluster a close second. In addition, partially and fully Mo-substituted clusters were investigated and found to have very low reorganization energies but too negative reduction potentials. The results provide a direct rationale why any substitution weakens the cluster as an electron carrier, and thus why the [Fe3S4] composition is optimal in the biological clusters.     

Content and health risk assessment of selected elements in the Yerba mate (Ilex paraguariensis,St. hillaire)

Element contents and radical scavenging activity in commercial Yerba mate tea blends from Paraguay and Argentina were determined. The potential health risk for the consumers was also calculated. Element contents in Yerba mate was arranged as follows: K > Ca > Mg > Mn > Fe > Zn > Na > Cu > Ni > Cr > Pb > Cd (leaves and stalks) and K > Mg > Mn > Ca > Zn > Na > Fe > Cu > Ni > Cr > Pb > Cd (infusion). In total 73% of K, 69% of Mn, 15% of Ni and Cu, 9% of Cr, 8% of Zn, 7% of Mg, 6% of Pb, 3% of Na, 2% of Cd, 0.34% of Ca, and 0.13% of Fe were extracted from leaves and stalks to the brew. Yerba mate tea was characterized by very high antioxidant activity. Argentinean Yerba mate had slightly higher antioxidant activity than Paraguayan. The combined non-carcinogenic effect (HI values) for each infusion and for all three infusion were below 1, which indicated that daily consumption of Yerba mate tea infusions did not cause essential non-carcinogenic health risk. The daily consumption of Yerba mate infusions provided necessary elements in the amounts significantly below 1% of the Recommended Dietary Allowance (RDA) daily intake. The exception was amount of Mn in I infusion from the despalada kind of Yerba mate, which was equal to 1.43% of RDA for men and 1.82% of RDA for women.     

Synthesis, characterization, and antitumor properties of some metal complexes of 2,6-diacetylpyridine bis(N4-azacyclic thiosemicarbazones)

Complexes of Mn(II), Fe(III), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Pt(II) with 2,6-diacetylpyridine bis(N4-azacyclic thiosemicarbazones), abbreviated as H2L, have been prepared and characterized by elemental analysis, molar conductance, magnetic moments (300-78 K) and spectral studies. On the basis of these studies, a distorted six-coordinate structure for Fe(L)Cl and a distorted five-coordinate structure for M(L) (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), or Pt(II] are suggested. The ligands undergo deprotonation and appear to coordinate through the thione sulphur, the imine nitrogen and pyridyl nitrogen. All the ligands and metal complexes were screened for their antitumor activity against P 388 lymphocytic leukemia test system in mice, and it was found that a few of them possess significant activity at the dosages used.     

Effects of sewage sludge application on heavy metal leaching from mine tailings impoundments

Column experiments were conducted to investigate the removal of heavy metals from two mine tailings (El Arteal and Jaravías) using sewage sludge as a reactive material. When sewage sludge is used as a reactive material on the El Arteal tailings (sample SA), Fe, Mn, Zn and Pb are removed and Cu and Ni are mobilized. The experiments carried out on the Jaravías tailings give similar results, showing the retention of Cu, Pb, Fe and Mn and the mobilization of Ni and Zn. An analysis performed using the PHREEQC numerical code suggests that the retention of Fe in the sewage sludge may be caused by the precipitation of Fe(OH)2.7Cl0.3 and possibly pyrite, and that the retention of Pb at high pH may be caused by the formation of stable phase minerals such as Pb(OH)2 and PbS in these conditions. Ni mobilization in the column experiments with the two tailings samples may be caused by the presence of significant amounts of leachable Ni in the sewage sludge. The complexation of metals with dissolved organic matter, calculated with the Minteq model, may be moderate.     

Synthesis, characterization and antitumor studies of Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes of N-salicyloyl-N'-o-hydroxythiobenzhydrazide

A new ligand N-salicyloyl-N'-o-hydroxythiobenzhydrazide (H2Sotbh) forms complexes [Mn(HSotbh)2], [Fe(Sotbh-H)(H2O)2], [M(Sotbh)] [M=Co(II), Cu(II) and Zn(II)] and [Ni(Sotbh)(H(2)O)2], which were characterized by various physico-chemical techniques. M?ssbauer spectrum of [Fe(Sotbh-H)(H2O)2] reveals the quantum admixture of 5/2 and 3/2 spin-states. Mn(II), Cu(II) and Ni(II) complexes were observed to inhibit the growth of tumor in vitro, whereas, Fe(III), Co(II), Zn(II) complexes did not. In vivo administration of Mn(II), Cu(II) and Ni(II) resulted in prolongation of survival of tumor bearing mice. Tumor bearing mice administered with Mn(II), Cu(II) and Ni(II) complexes showed reversal of tumor growth associated induction of apoptosis in lymphocytes. The paper discusses the possible mechanisms and therapeutic implication of the H2Sotbh and its metal complexes in tumor regression and tumor growth associated immunosuppression.     

Selective adsorption of apoferritin on immobilized Fe(III): demonstration of Fe(III) binding sites

Immobilized metal ion affinity chromatography has been used to demonstrate and partially characterize Fe(III) binding sites on apoferritin. Binding of Fe(III) to these sites is influenced by pH, but not affected by high ionic strength. These results suggest that both ionic and coordinate covalent interactions are important in the formation of the Fe(III): apoferritin complex. This is, to our knowledge, the first demonstration of direct Fe(III) binding to apoferritin. Other immobilized metal ions, including Zn(II), Ni(II), Cu(II), Cr(III), Co(II), and Tb(III), displayed little or no adsorption of apoferritin. The analytical technique of immobilized metal ion affinity chromatography also shows great promise in the purification of apoferritin, ferritin, and other iron-binding proteins.     

The reaction mechanism of the Ga(III)Zn(II) derivative of uteroferrin and corresponding biomimetics

Purple acid phosphatase from pig uterine fluid (uteroferrin), a representative of the diverse family of binuclear metallohydrolases, requires a heterovalent Fe(III)Fe(II) center for catalytic activity. The active-site structure and reaction mechanism of this enzyme were probed with a combination of methods including metal ion replacement and biomimetic studies. Specifically, the asymmetric ligand 2-bis{[(2-pyridylmethyl)-aminomethyl]-6-[(2-hydroxybenzyl)(2-pyridylmethyl)]aminomethyl}-4-methylphenol and two symmetric analogues that contain the softer and harder sites of the asymmetric unit were employed to assess the site selectivity of the trivalent and divalent metal ions using (71)Ga NMR, mass spectrometry and X-ray crystallography. An exclusive preference of the harder site of the asymmetric ligand for the trivalent metal ion was observed. Comparison of the reactivities of the biomimetics with Ga(III)Zn(II) and Fe(III)Zn(II) centers indicates a higher turnover for the former, suggesting that the M(III)-bound hydroxide acts as the reaction-initiating nucleophile. Catalytically active Ga(III)Zn(II) and Fe(III)Zn(II) derivatives were also generated in the active site of uteroferrin. As in the case of the biomimetics, the Ga(III) derivative has increased reactivity, and a comparison of the pH dependence of the catalytic parameters of native uteroferrin and its metal ion derivatives supports a flexible mechanistic strategy whereby both the mu-(hydr)oxide and the terminal M(III)-bound hydroxide can act as nucleophiles, depending on the metal ion composition, the geometry of the second coordination sphere and the substrate.     

Metal Complexes of 2,6-Diacetylpyridine Bis(thiosemicarbazone): their Preparation,Characterization and Antitumour Activity

Complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Pt(II) with 2.6-diacetylpyridine bis(thiosemicarbazone) (daptsc-H₂) have been isolated and characterized by elemental analysis, conductance measurements, magnetic susceptibilities (from room temperature to liquid nitrogen temperature), diffuse reflectance and infrared studies. On the basis of these studies a seven-coordinate structure for Zn(daptsc-H₂)(OAc)₂, a six-coordinate structure for M(daptsc-H₂)Cl₂ (MMn(II), Co(Il), Ni(II) or Cu(II)) and Fe(daptsc-H₂)SO₄, and a five-coordinate structure for Pt(daptsc) are suggested. ⁵⁷Fe Mössbauer spectra at 300 and 78 K also suggest a distorted octahedral structure with d_xy ground state for Fe(daptsc-H₂)SO₄ complex. All these metal(II) complexes have been screened for their antitumour activity in the P388 lymphocytic leukaemia test system in mice and showed enhanced antitumour activity relative to the free ligand.     

Relationship between Mikania micrantha invasion and soil microbial biomass, respiration and functional diversity

The aim of this study was to determine elemental composition of sap-feeding insects inhabiting various parts of the Ni hyperaccumulating plant Berkheya coddii Roessl., the endemic species of ultramafic outcrops in Mpumalanga, South Africa. Three species were examined: the aphid Protaphis pseudocardui (Aphididae), abundant on young leaves; the mealybug Orthesia sp. (Ortheziidae) colonizing underground parts of this plant, and the bug Norialsus berkheyae (Cixiidae) living on young shoots. Maps of Ni, K, Ca, Zn, and Fe for selected body areas of these species were generated using Dynamic Analysis method on the basis of particle-induced X-ray emission (micro-PIXE) and proton backscattering (BS) measurements. Atomic absorption spectrometry was used to determine Ni, Zn, Cu, Fe contents in the B. coddii organs, in some sap-feeding insect species including these mentioned above, and in the assassin bug hunting on Chrysolina pardalina, a monophagous beetle of B. coddii. Bioaccumulation factor for Ni in the examined species was below 0.05, and much higher for other metals (Zn ≥ 2; Fe ≤ 5). Ni distribution within body was species-dependent. It was the highest in the antennae of P. pseudocardui, in the head of Orthesia sp. and in the metathorax of N. berkheyae. Distribution patterns of other metals were different among examined species. Ca was recorded mainly in peripheral parts of the body in all species. Zn showed similar distribution to Ni. Fe distribution was similar to Ni only in the mealybugs. Uneven concentrations of metals within selected body regions indicated their relations with specific organs. Analysis of Ni transfer to higher trophic levels was done on the basis of two food nets: B. coddii—C. pardalina—Rhinocoris neavii and B. coddii—P. pseudocardui—Polyrhachis ant and led to the conclusion that the role of sap-feeding insects in Ni transfer was marginal.     

Relationships of nicotianamine and other amino acids with nickel, zinc and iron in Thlaspi hyperaccumulators

Experimental evidence suggests that nicotianamine (NA) is involved in the complexation of metal ions in some metal-hyperaccumulating plants. Closely-related nickel (Ni)- and zinc (Zn)-hyperaccumulating species were studied to determine whether a correlation exists between the Ni and Zn concentrations and NA in foliar tissues. A liquid chromatography-mass spectrometry (LC-MS) procedure was developed to quantify the NA and amino acid contents using the derivatizing agent 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate. A strong correlation emerged between Ni and NA, but not between Zn and NA. Concentrations of NA and L-histidine (His) also increased in response to higher Ni concentrations in the hydroponic solution supplied to a serpentine population of Thlaspi caerulescens. An inversely proportional correlation was found between the iron (Fe) and Ni concentrations in the leaves. Correlations were also found between Zn and asparagine. The results obtained in this study suggest that NA is involved in hyperaccumulation of Ni but not Zn. The inverse proportionality between the Ni and Fe concentrations in the leaf may suggest that Ni and Fe compete for complexation to NA.     

Suberoylanilide hydroxamic acid, a potent histone deacetylase inhibitor; its X-ray crystal structure and solid state and solution studies of its Zn(II), Ni(II), Cu(II) and Fe(III) complexes

Reaction of the potent hydroxamate-based histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA), with hydrated metal salts of Fe(III), Cu(II), Ni(II) and Zn(II) yielded a tris-hydroxamato complex in the case of Fe(III) and bis-hydroxamato complexes in the case of Cu(II), Ni(II) and Zn(II) both in the solid state and in solution. Reaction of the secondary hydroxamic acid, N-Me-SAHA, also yielded a tris-hydroxamato complex in the case of Fe(III) and bis-hydroxamato complexes in the case of Cu(II), Ni(II) and Zn(II) in solution. These metal complexes have the hydroxamato moiety coordinated in an O,O’-bidentate fashion. Stability constants of the metal complexes formed with SAHA and N-Me-SAHA in a DMSO/H₂O 70/30%(v/v) mixture are described. A novel crystal structure of SAHA together with a novel synthesis for N-Me-SAHA are also reported.     

The budget of dissolved trace metals in Lake Biwa,Japan

A comprehensive study on the dynamics of dissolved elements (Mg, Al, Si, P, Ca, V, Cr, Mn, Fe, Ni, Zn, As, Sr, Y, W, and U) in Lake Biwa was carried out using a clean technique. Lake water samples (n = 523) were collected from six stations in the North Basin and three stations in the South Basin. River water samples (n = 178) were collected from 14 major rivers flowing into the North Basin. Rainwater samples (n = 89) were collected at Otsu. The river water was enriched with Mn, Al, Fe, P, and Zn and the rainwater was enriched with Zn, Al, Fe, and Mn compared to North Basin water during winter mixing. The residence times of dissolved species were estimated on the basis of input through the rivers and rain. The residence times for Ca, Mg, and Sr were about 8 years, the same as that for water. Mn, Al, Fe, and Zn showed the shortest residence times (0.05–0.19 year). A budget calculation suggested that more than 60% of the input of dissolved Si, P, V, Cr, Mn, Fe, Ni, and Zn was scavenged and retained in the lake sediments and/or discharged as suspended particles.     

Reaction of a model siderophore with Ni(II), Co(II) and Zn(II) in aqueous solution: kinetics and spectroscopy

A spectroscopic study was performed showing that the [Fe(III)(L(2-))(2)](1-) (L(2-)=dopacatecholate) complex reacts with Ni(II), Co(II) and Zn(II) in an aqueous solution containing S(2)O(3)(2-) resulting in the soluble [M(L(1-))(3)](1-) (L(1-)=dopasemiquinone; M=Ni(II), Co(II) or Zn(II) complex species. The Raman and IR spectra of the [CTA][M(L(1-))(3)] complexes, CTA=hexadecyltrimethylammonium cation, in the solid state were obtained. The kinetic constants for the metal substitution reactions were determined at four different temperatures, providing values for DeltaH(not equal), DeltaS(not equal) and DeltaG(not equal). The reactions were slow (k=10(-11) Ms(-1)) and endothermic. The system investigated can be considered as a simplified model to explain some aspects of siderophore chemistry.     

Effects of heavy metals on both induction and function of root Fe(lll) reductase in Fe-deficient cucumber (Cucumis sativus L.) plants

Heavy metals are known to induce Fe chlorosis in different plantspecies. Heavy-metal-induced chlorosis is generally correlatedwith low plant Fe contents, suggesting effects of heavy metalson Fe mobilization and uptake. Under Fe-deficient conditions,dicotyledonous plants enhance root Fe(lll) reductase activity,thus increasing the capacity to reduce Fe(MI) to Fe(ll), theform in which roots absorb Fe. We studied the effect of severalheavy metals (Mn, Pb, Zn, Mo, Ni, Cu, and Cd) on the inductionof enhanced root Fe(lll) reductase by 11-d-old Fe-deficientcucumber [Cucumis sativus L. cv. Ashley). The effect of theseheavy metals on the function of the induced Fe(lll) reductasewas also investigated. Results showed that some heavy metalscan inhibit both the induction and function of root Fe(lll)reductase. Ni, at 20//M, and Cu and Cd, at 5 fiM concentrationor higher, severely inhibited the induction of root Fe(lll)reductase while Mn, Pb, Zn, and Mo had little effect, even atconcentrations higher than 20 //M. Function of the induced rootFe(lll) reductase only was negatively affected by Cu and Ni. Key words: Cucumis sativus, iron deficiency, iron reduction, heavy metals     

Alkylating ability of artemisinin after Cu(I)-induced activation

The reductive activation of artemisinin by copper(I)-dipyrrin or copper(I)-(2-Clip-Phen) complexes generates an artemisinin derived alkylating species leading to covalent artemisinin–copper complex adducts. The reactivity of the peroxide function of artemisinin toward Cu(I) complexes is similar to that of Fe(II) analogues, even though the reaction is more sluggish and product distribution slightly different.     

Differences in Trace Metal Concentrations (Co, Cu, Fe, Mn, Zn, Cd, and Ni) in Whole Blood, Plasma, and Urine of Obese and Nonobese Children

High-performance ion chromatography and inductively coupled plasma–mass spectrometry methods have been applied to estimate the content of Cd, Co, Cu, Fe, Mn, Zn, and Ni in whole blood, plasma, and urine of obese and nonobese children. The study was conducted on a group of 81 Polish children of age 6–17 years (37 males, 44 females). Obese children were defined as those with body mass index (BMI) >95th percentile in each age–gender-specific group. Statistical testing was done by the use of nonparametric tests (Kruskal–Wallis's and Mann–Whitney's U) and Spearman's correlation coefficient. Significant correlations appeared for control group in plasma (Mn–Cd, Ni–Co), urine (Cu–Co), and blood (Fe–Cu), while for obese patients in plasma (Cd–Mn, Ni–Cu, Ni–Zn) and urine (Fe–Cd, Co–Mn). Sex criteria did not influence correlations between metals' content in plasma and urine of obese patients. Metals' abundance was correlated in non-corresponding combinations of body fluids. Rare significant differences between content of metals according to sex and the type of body fluids were discovered: Zn in plasma from obese patients of both sexes, and Zn, Co, and Mn in blood, Mn in plasma from healthy subjects. Negative correlations between BMI and Zn in blood, Cu in plasma, and Fe in urine were discovered for girls (control group). Positive correlation between Co content in plasma and BMI was discovered for obese boys. The changes in metals' content in body fluids may be indicators of obesity. Content of zinc, copper, and cobalt should be monitored in children with elevated BMI to avoid deficiency problems.