Co(II), Cd(II), Hg(II) and U(VI)O₂ complexes of o-hydroxyacetophenone[N-(3-hydroxy-2-naphthoyl)] hydrazone: physicochemical study, thermal studies and antimicrobial activity

The o-Hydroxy acetophenone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H(2)o-HAHNH) has been prepared and its structure is confirmed by elemental analysis, IR, (1)H NMR and (13)C NMR spectroscopy. It has been used to produce diverse complexes with Co(II), Cd(II), Hg(II) and U(VI)O(2) ions. The isolated complexes have been investigated by elemental analysis, magnetic measurements, molar conductivity, thermal (TG, DTG) and spectral ((1)H NMR, (13)C NMR, IR, UV-visible, MS) studies. Infrared spectra suggested H(2)o-HAHNH acts as a bidentate and/or tridentate ligand. The electronic spectrum of [Co(Ho-HAHNH)(2)] complex as well as its magnetic moments suggesting octahedral geometry around Co(II) center. The TG analyses suggest high stability for most complexes followed by thermal decomposition in different steps. Moreover, the kinetic and thermodynamic parameters (Ea, A, ΔH, ΔS and ΔG) for the different decomposition steps of the [Co(Ho-HAHNH)(2)] and [Cd(Ho-HAHNH)(2)] complexes were calculated using the Coats-Redfern and Horowitz-Metzger methods. Moreover, the antibacterial and antifungal activities of the isolated compounds were studied using a wide spectrum of bacterial and fungal strains.

Ligational behavior of thiosemicarbazone, semicarbazone and thiocarbohydrazone ligands towards VO(IV), Ce(III), Th(IV) and UO2(VI) ions: synthesis, structural characterization and biological studies

Mono- and binuclear VO(IV), Ce(III), Th(IV) and UO(2)(VI) complexes of thiosemicarbazone, semicarbazone and thiocarbohydrazone ligands derived from 4,6-diacetylresorcinol were synthesized. The structures of these complexes were elucidated by elemental analyses, IR, UV-vis, ESR, (1)H NMR and mass spectra as well as conductivity and magnetic susceptibility measurements and thermal analyses. The thiosemicarbazone (H(4)L(1)) and the semicarbazone (H(4)L(2)) ligands behave as dibasic pentadentate ligands in case of VO(IV) and UO(2)(VI) complexes, tribasic pentadentate in case of Ce(III) complexes and monobasic pentadentate in case of Th(IV) complexes. However, the thiocarbohydrazone ligand (H(3)L(3)) acts as a monobasic tridentate ligand in all complexes except the VO(IV) complex in which it acts as a dibasic tridentate ligand. The antibacterial and antifungal activities were also tested against Rhizobium bacteria and Fusarium-Oxysporium fungus. The metal complexes of H(4)L(1) ligand showed a higher antibacterial effect than the free ligand while the other ligands (H(4)L(2) and H(3)L(3)) showed a higher effect than their metal complexes. The antifungal effect of all metal complexes is lower than the free ligands.

Changes in sleep-wake cycle after chronic exposure to uranium in rats

Uranium is a heavy metal known to induce toxicity in kidneys. It is also known to enter the central nervous system, thus inducing neurophysiological effects, after exposure to relatively high concentrations. The effect of chronic uranium exposure (40 mg l(-1) in drinking water, for 90 days) on electroencephalographic architecture has been studied on freely moving rats using a telemetry technique. The main effects of uranium on the sleep-wake cycle were an increase in rapid eye movement sleep (REM-sleep) and theta band power during the light period, as early as Day 30 after exposure commenced. The most probable explanation for these effects is that uranium directly affects the brain. This increase in REM-sleep was previously described in human depression or models of chronically stressed rats and it may be assimilated with some protective or compensatory mechanisms.

[Malignant transformation of human bronchial epithelial cell (BEAS-2B) induced by depleted uranium]

BACKGROUND & OBJECTIVE

It is clear from works already reported that depleted uranium (DU) affect human health. However, the late effect, especially the carcinogenesis, was not clearly understood. This study was designed to investigate the malignant transformation of human bronchial epithelial cell induced by insoluble DU and lung cancer related gene expression pattern, through imitating the condition that human absorbs depleted uranium aerosol.

METHODS

Adenovirus-12/SV40 virus immortalized human bronchial epithelial cells (BEAS-2B) were reacted with insoluble DU oxide (dUO2); the characteristics of malignant transformation of cells were identified through observing the multiplication time of different generation cells, serum resistance, colony formation rate of semi-solid agar, and tumorigenesis in nude mice. Gene expression pattern of transferred BEAS-2B cell induced by DU was determined using 213 lung cancer related gene arrays.

RESULTS

The multiplication time of BEAS-2B cell treated with DU was obviously decreased and the serum reistance was significantly increased in 5th generation; the anchorage independent growth (semi-solid agar colony formation) was appeared in 10th generation cell. The 15th generation cell formed tumor in nude mice. DMSO showed overt protection effect on malignant transformation of BEAS-2B cell. The analyzing results of 213 lung cancer related gene arrays showed that the expression level changed in more than 70 genes of transferred cells, including the overt decrease of level of gene expression in more than 10 genes.

CONCLUSION

DU has carcinogenesis in vitro.

The effect of heavy metals and other environmental conditions on the anaerobic phosphate metabolism of Acinetobacter johnsonii

A strain of Acinetobacter with potential for bioremediation of heavy metal-contaminated waters was isolated from a wastewater-treatment plant operating an enhanced biological phosphate removal process. NMR and extractive methods showed that polyphosphate accumulated aerobically was degraded under anaerobic conditions both in the presence and absence of cadmium or uranium (0.2-0.5 mM). NMR showed that free phosphate was formed at the expense of polyphosphate, and an extractive technique indicated that this reaction could be stimulated by the presence of UO(2)2+ under these conditions. Energy-dispersive X-ray microanalysis demonstrated that only cadmium could enter the cells, and co-localized with intra-cellular granules containing phosphate and other divalent metals. The effects of other environmental parameters on the anaerobic phosphate metabolism were also investigated. Between pH 5.5 and 8.0, phosphate release increased with increasing pH. Between 4 degrees C and 37 degrees C, phosphate release increased with increasing temperature. The presence of nitrate at concentrations of 10 mM and above inhibited anoxic phosphate release, but supplying tungstate in the growth medium prior to anoxic incubation reduced the production of active nitrate reductase and alleviated this effect.

The effects of the initial lung deposit on uranium biokinetics after administration as UF4 and UO4

This study was designed to assess the effect of the initial lung deposit (ILD) on uranium biokinetics in rats after intracheal instillation of biologically soluble uranium compounds. Rats received various doses of either UO4 or UF4 dust. The uranium content was determined in the kidneys, lungs, remaining carcass, urine and faeces at intervals of up to 30 days. The percentages of uranium absorbed into blood, transferred to tissues, and excreted in urine were independent of the uranium lung deposit for the two compounds. The K/K + U ratio 24 h after installation (K is the per cent of uranium retained in the kidneys and U the per cent excreted in urine) which can be used to evaluate kidney function, was essentially constant in the range from 0.02 to 12.5 microg U g(-1) kidneys.

Sequence/structure selective thermal and photochemical cleavage of yeast-tRNA(Phe) by UO(2)2+

The uranyl(VI) ion, UO(2)2+, cleaves yeast tRNA(Phe) both thermally and photochemically. Photochemical cleavage takes place at all positions but exhibits maxima at G10, G18, G30, A38, C49 and A62. Furthermore, in the presence of stoichiometric concentrations of citrate, the cleavage is generally suppressed except that strong cleavage at positions G10 and C48-U50 persists, indicating the presence of a high-affinity metal-ion binding site. It is proposed that these photocleavage sites reflect the tertiary structure of the yeast tRNA(Phe) molecule in terms of D-loop/T-loop interaction and anticodon loop conformation and that uranyl-mediated photocleavage of RNA may be used as a probe of RNA tertiary structure, and in particular for identifying binding sites for divalent metal ions. Thus a high-affinity metal-ion binding site is inferred in the "central pocket" formed by the D-loop, and the acceptor stem.

Investigation of monovalent cation activation of S-adenosylmethionine synthetase using mutagenesis and uranyl inhibition

S-Adenosylmethionine (AdoMet) synthetase catalyzes the formation of AdoMet from ATP and L-methionine with subsequent hydrolysis of the bound tripolyphosphate intermediate. Maximal activity requires the presence of two divalent and one monovalent cation per active site. Recently, the x-ray structure of the Escherichia coli AdoMet synthetase was solved, and the positions of the two Mg2+ binding sites were identified. Based on additional spherical electron density, the K+ binding site was postulated to be a nearby site where the uranyl heavy atom derivative also bound in the crystal. The side chain of glutamate 42 is within ligation distance of the metals. Mutagenesis of glutamate 42 to glutamine (E42QMetK) abolished monovalent cation activation and produced an enzyme that has kinetic properties virtually identical to those of K(+)-free wild type AdoMet synthetase in both the overall AdoMet synthetase reaction and in the hydrolysis of tripolyphosphate. Thus, there is a approximately 100-fold decrease in the Vmax for AdoMet synthesis and large increases in the Km values for both substrates. In contrast there is only a 2-fold decrease in Vmax for tripolyphosphate hydrolysis. The uranyl ion, UO2(2+), is a competitive inhibitor with respect to K+ (Ki = 350 nM) and is the first ion to bind at this site and inhibit the enzyme. The UO2(2+) inhibition is reversible and tight-binding, and results from UO2(2+) and not UO2(2+)-ATP. Analogous to K+ activation, UO2(2+) predominantly inhibits AdoMet formation rather than tripolyphosphate hydrolysis. The kinetic results indicate that UO2(2+) inhibition is likely to result from interference with productive ATP binding. UO2(2+) remains a tight-binding inhibitor of the E42Q mutant, which suggests that K+ and UO2(2+) have different ligation preferences when bound in the monovalent cation binding pocket. The results support the model that glutamate 42 provides ligands to the K+ and has a major role in monovalent cation binding.