The Experts below are selected from a list of 63441 Experts worldwide ranked by ideXlab platform
A Hartwig - One of the best experts on this subject based on the ideXlab platform.
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zinc finger proteins as potential targets for Toxic Metal ions differential effects on structure and function
Antioxidants & Redox Signaling, 2001Co-Authors: A HartwigAbstract:Zinc finger structures are frequently found in transcription factors and DNA repair proteins, mediating DNA-protein and protein-protein binding. As low concentrations of transition Metal compounds, including those of cadmium, nickel, and cobalt, have been shown to interfere with DNA transcription and repair, several studies have been conducted to elucidate potential interactions of Toxic Metal ions with zinc-binding protein domains. Various effects have been identified, including the displacement of zinc, e.g., by cadmium or cobalt, the formation of mixed complexes, incomplete coordination of Toxic Metal ions, as well as the oxidation of cysteine residues within the Metal-binding domain. Besides the number of cysteine and/or histidine ligands, unique structural features of the respective protein under investigation determine whether or not zinc finger structures are disrupted by one or more transition Metals. As improper folding of zinc finger domains is mostly associated with the loss of correct protein function, disruption of zinc finger structures may result in interference with manifold cellular processes involved in gene expression, growth regulation, and maintenance of the genomic integrity.
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differential effects of Toxic Metal compounds on the activities of fpg and xpa two zinc finger proteins involved in dna repair
Carcinogenesis, 2000Co-Authors: M Asmuss, Leon H.f. Mullenders, Andre P M Eker, A HartwigAbstract:Even though not mutagenic, compounds of the carcinogenic Metals nickel, cadmium, cobalt and arsenic have been shown previously to inhibit nucleotide excision repair and base excision repair at low, non-cytoToxic concentrations. Since some Toxic Metals have high affinities for -SH groups, we used the bacterial formamidopyrimidine-DNA glycosylase (Fpg protein) and the mammalian XPA protein as models to investigate whether zinc finger structures in DNA repair enzymes are particularly sensitive to carcinogenic and/or Toxic Metal compounds. Concentrations of zinc finger structures may be sensitive targets for Toxic Metal compounds, but each zinc finger protein has unique sensitivities.
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Interference by Toxic Metal compounds with isolated zinc finger DNA repair proteins.
Toxicology letters, 2000Co-Authors: M Asmuss, Leon H.f. Mullenders, A HartwigAbstract:Compounds of nickel, cadmium, cobalt and arsenic have been shown previously to inhibit DNA repair processes at low concentrations. In the present study we investigated whether this repair inhibition may be caused by the displacement of zinc in zinc finger structures of DNA repair proteins. As models, the bacterial formamidopyrimidine-DNA glycosylase (Fpg) and the mammalian XPA protein were applied. Both proteins were inhibited by Cd(II) and Cu(II). Hg(II) strongly inhibited the Fpg protein, but did not affect the XPA protein. In contrast, the XPA protein was disturbed by Co(II) and Ni(II), while the activity of the Fpg protein was not reduced. Neither protein was inhibited by As(III) or Pb(II). Thus, each zinc finger protein appears to have its own structural features and sensitivities towards Toxic Metal ions. Furthermore, each Metal exerts specific mechanisms leading to DNA repair inhibition.
Geoffrey M. Gadd - One of the best experts on this subject based on the ideXlab platform.
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X-ray absorption spectroscopy (XAS) of Toxic Metal mineral transformations by fungi.
Environmental microbiology, 2007Co-Authors: Marina Fomina, John M. Charnock, Andrew D. Bowen, Geoffrey M. GaddAbstract:Fungi can be highly efficient biogeochemical agents and accumulators of soluble and particulate forms of Metals. This work aims to understand some of the physico-chemical mechanisms involved in Toxic Metal transformations focusing on the speciation of Metals accumulated by fungi and mycorrhizal associations. The amorphous state or poor crystallinity of Metal complexes within biomass and relatively low Metal concentrations make the determination of Metal speciation in biological systems a challenging problem but this can be overcome by using synchrotron-based element-specific X-ray absorption spectroscopy (XAS) techniques. In this research, we have exposed fungi and ectomycorrhizas to a variety of copper-, zinc- and lead-containing minerals. X-ray absorption spectroscopy studies revealed that oxygen ligands (phosphate, carboxylate) played a major role in Toxic Metal coordination within the fungal and ectomycorrhizal biomass during the accumulation of mobilized Toxic Metals. Coordination of Toxic Metals within biomass depended on the fungal species, initial mineral composition, the nitrogen source, and the physiological state/age of the fungal mycelium.
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Solubilization of Toxic Metal minerals and Metal tolerance of mycorrhizal fungi
Soil Biology and Biochemistry, 2005Co-Authors: Marina Fomina, Ian J. Alexander, Jan V. Colpaert, Geoffrey M. GaddAbstract:Abstract This work investigates the ability of ericoid mycorrhizal (ErM) and ectomycorrhizal (EcM) fungi to solubilize different Toxic Metal (Cd, Cu, Pb, Zn)-containing minerals. Minerals were incorporated into solidified agar media and solubilization assessed by measuring clearing of the agar after fungal growth. Measurement of radial growth and biomass dry weight provided indications of Metal tolerance: accumulated Metal in the biomass was measured by atomic absorption spectrophotometry. Metal tolerance and solubilizing ability varied widely between different mineral and fungal species, and strains derived from sites of differing degrees of Metal pollution. Zinc phosphate exhibited the least Toxicity and was the easiest to solubilize by the majority of tested fungal isolates. Solubilization of Toxic Metal minerals was connected with both the pH of the medium and growth and tolerance of fungi and it seems that acidification of the medium was the main mechanism of mineral dissolution for most of the mycorrhizal fungi studied. A very strong lethal effect was observed for ectomycorrhizal isolates (>60% of strains) in the presence of Pb phosphate, carbonate, sulphide and tetraoxide. In contrast, ericoid mycorrhizal isolates were able to grow on Pb-mineral-amended media. A significant proportion of ericoid mycorrhizal cultures (70–90%) solubilized Cd and Cu phosphates and cuprite. None of the ericoid mycorrhizal and ectomycorrhizal fungi were able to produce a clear zone in Pb mineral-containing agar. However, many fungi were able to accumulate mobilized Pb in their mycelia. Differences in Toxic Metal mineral tolerance, mineral solubilization and Metal uptake between populations isolated from Metal-polluted and uncontaminated sites were related to the Toxic Metal which was the main pollutant in the original contaminated environment. In general, Metal-tolerant fungi grew and solubilized Toxic Metal minerals better than non-tolerant isolates.
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role of oxalic acid overexcretion in transformations of Toxic Metal minerals by beauveria caledonica
Applied and Environmental Microbiology, 2005Co-Authors: Marina Fomina, Ian J. Alexander, S J Hillier, J M Charnock, K Melville, Geoffrey M. GaddAbstract:The fungus Beauveria caledonica was highly tolerant to Toxic Metals and solubilized cadmium, copper, lead, and zinc minerals, converting them into oxalates. This fungus was found to overexcrete organic acids with strong Metal-chelating properties (oxalic and citric acids), suggesting that a ligand-promoted mechanism was the main mechanism of mineral dissolution. Our data also suggested that oxalic acid was the main mineral-transforming agent. Cadmium, copper, and zinc oxalates were precipitated by the fungus in the local environment and also in association with the mycelium. The presence of Toxic Metal minerals often led to the formation of mycelial cords, and in the presence of copper-containing minerals, these cords exhibited enhanced excretion of oxalic acid, which resulted in considerable encrustation of the cords by copper oxalate hydrate (moolooite). It was found that B. caledonica hyphae and cords were covered by a thick hydrated mucilaginous sheath which provided a microenvironment for chemical reactions, crystal deposition, and growth. Cryo-scanning electron microscopy revealed that mycogenic Metal oxalates overgrew parental fungal hyphae, leaving a labyrinth of fungal tunnels within the newly formed mineral matter. X-ray absorption spectroscopy revealed that oxygen ligands played a major role in Metal coordination within the fungal biomass during the accumulation of mobilized Toxic Metals by B. caledonica mycelium; these ligands were carboxylic groups in copper phosphate-containing medium and phosphate groups in pyromorphite-containing medium.
Lianzhou Wang - One of the best experts on this subject based on the ideXlab platform.
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addressing Toxicity of lead progress and applications of low Toxic Metal halide perovskites and their derivatives
Advanced Energy Materials, 2017Co-Authors: Miaoqiang Lyu, Jungho Yun, Peng Chen, Mengmeng Hao, Lianzhou WangAbstract:Metal halide perovskites have been brought to the forefront of research focus in solution-processable photovoltaics, with the device efficiency swiftly surging to over 22% over the past few years. The state-of-the-art Metal halide perovskites that have been intensively investigated include Toxic lead, which potentially hampers their commercialization process. To address this Toxicity issue, intensive recent research effort has been devoted to developing low-Toxic Metal halide perovskites and their derivatives for photovoltaic applications. Herein, the recent research progress achieved so far in addressing the Toxicity issue of lead halide perovskites in photovoltaics is summarized. By comparing the merits and drawbacks of different low-Toxic Metal halide systems, the current challenges and opportunities in the photovoltaic field are highlighted. Potential low-Toxic Metal halide perovskites and their derivatives are also discussed from the perspective of theoretical calculations. Furthermore, promising applications of low-Toxic Metal halide perovskites beyond the photovoltaic sector are briefly discussed.
Marina Fomina - One of the best experts on this subject based on the ideXlab platform.
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X-ray absorption spectroscopy (XAS) of Toxic Metal mineral transformations by fungi.
Environmental microbiology, 2007Co-Authors: Marina Fomina, John M. Charnock, Andrew D. Bowen, Geoffrey M. GaddAbstract:Fungi can be highly efficient biogeochemical agents and accumulators of soluble and particulate forms of Metals. This work aims to understand some of the physico-chemical mechanisms involved in Toxic Metal transformations focusing on the speciation of Metals accumulated by fungi and mycorrhizal associations. The amorphous state or poor crystallinity of Metal complexes within biomass and relatively low Metal concentrations make the determination of Metal speciation in biological systems a challenging problem but this can be overcome by using synchrotron-based element-specific X-ray absorption spectroscopy (XAS) techniques. In this research, we have exposed fungi and ectomycorrhizas to a variety of copper-, zinc- and lead-containing minerals. X-ray absorption spectroscopy studies revealed that oxygen ligands (phosphate, carboxylate) played a major role in Toxic Metal coordination within the fungal and ectomycorrhizal biomass during the accumulation of mobilized Toxic Metals. Coordination of Toxic Metals within biomass depended on the fungal species, initial mineral composition, the nitrogen source, and the physiological state/age of the fungal mycelium.
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Solubilization of Toxic Metal minerals and Metal tolerance of mycorrhizal fungi
Soil Biology and Biochemistry, 2005Co-Authors: Marina Fomina, Ian J. Alexander, Jan V. Colpaert, Geoffrey M. GaddAbstract:Abstract This work investigates the ability of ericoid mycorrhizal (ErM) and ectomycorrhizal (EcM) fungi to solubilize different Toxic Metal (Cd, Cu, Pb, Zn)-containing minerals. Minerals were incorporated into solidified agar media and solubilization assessed by measuring clearing of the agar after fungal growth. Measurement of radial growth and biomass dry weight provided indications of Metal tolerance: accumulated Metal in the biomass was measured by atomic absorption spectrophotometry. Metal tolerance and solubilizing ability varied widely between different mineral and fungal species, and strains derived from sites of differing degrees of Metal pollution. Zinc phosphate exhibited the least Toxicity and was the easiest to solubilize by the majority of tested fungal isolates. Solubilization of Toxic Metal minerals was connected with both the pH of the medium and growth and tolerance of fungi and it seems that acidification of the medium was the main mechanism of mineral dissolution for most of the mycorrhizal fungi studied. A very strong lethal effect was observed for ectomycorrhizal isolates (>60% of strains) in the presence of Pb phosphate, carbonate, sulphide and tetraoxide. In contrast, ericoid mycorrhizal isolates were able to grow on Pb-mineral-amended media. A significant proportion of ericoid mycorrhizal cultures (70–90%) solubilized Cd and Cu phosphates and cuprite. None of the ericoid mycorrhizal and ectomycorrhizal fungi were able to produce a clear zone in Pb mineral-containing agar. However, many fungi were able to accumulate mobilized Pb in their mycelia. Differences in Toxic Metal mineral tolerance, mineral solubilization and Metal uptake between populations isolated from Metal-polluted and uncontaminated sites were related to the Toxic Metal which was the main pollutant in the original contaminated environment. In general, Metal-tolerant fungi grew and solubilized Toxic Metal minerals better than non-tolerant isolates.
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role of oxalic acid overexcretion in transformations of Toxic Metal minerals by beauveria caledonica
Applied and Environmental Microbiology, 2005Co-Authors: Marina Fomina, Ian J. Alexander, S J Hillier, J M Charnock, K Melville, Geoffrey M. GaddAbstract:The fungus Beauveria caledonica was highly tolerant to Toxic Metals and solubilized cadmium, copper, lead, and zinc minerals, converting them into oxalates. This fungus was found to overexcrete organic acids with strong Metal-chelating properties (oxalic and citric acids), suggesting that a ligand-promoted mechanism was the main mechanism of mineral dissolution. Our data also suggested that oxalic acid was the main mineral-transforming agent. Cadmium, copper, and zinc oxalates were precipitated by the fungus in the local environment and also in association with the mycelium. The presence of Toxic Metal minerals often led to the formation of mycelial cords, and in the presence of copper-containing minerals, these cords exhibited enhanced excretion of oxalic acid, which resulted in considerable encrustation of the cords by copper oxalate hydrate (moolooite). It was found that B. caledonica hyphae and cords were covered by a thick hydrated mucilaginous sheath which provided a microenvironment for chemical reactions, crystal deposition, and growth. Cryo-scanning electron microscopy revealed that mycogenic Metal oxalates overgrew parental fungal hyphae, leaving a labyrinth of fungal tunnels within the newly formed mineral matter. X-ray absorption spectroscopy revealed that oxygen ligands played a major role in Metal coordination within the fungal biomass during the accumulation of mobilized Toxic Metals by B. caledonica mycelium; these ligands were carboxylic groups in copper phosphate-containing medium and phosphate groups in pyromorphite-containing medium.
M Asmuss - One of the best experts on this subject based on the ideXlab platform.
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differential effects of Toxic Metal compounds on the activities of fpg and xpa two zinc finger proteins involved in dna repair
Carcinogenesis, 2000Co-Authors: M Asmuss, Leon H.f. Mullenders, Andre P M Eker, A HartwigAbstract:Even though not mutagenic, compounds of the carcinogenic Metals nickel, cadmium, cobalt and arsenic have been shown previously to inhibit nucleotide excision repair and base excision repair at low, non-cytoToxic concentrations. Since some Toxic Metals have high affinities for -SH groups, we used the bacterial formamidopyrimidine-DNA glycosylase (Fpg protein) and the mammalian XPA protein as models to investigate whether zinc finger structures in DNA repair enzymes are particularly sensitive to carcinogenic and/or Toxic Metal compounds. Concentrations of zinc finger structures may be sensitive targets for Toxic Metal compounds, but each zinc finger protein has unique sensitivities.
-
Interference by Toxic Metal compounds with isolated zinc finger DNA repair proteins.
Toxicology letters, 2000Co-Authors: M Asmuss, Leon H.f. Mullenders, A HartwigAbstract:Compounds of nickel, cadmium, cobalt and arsenic have been shown previously to inhibit DNA repair processes at low concentrations. In the present study we investigated whether this repair inhibition may be caused by the displacement of zinc in zinc finger structures of DNA repair proteins. As models, the bacterial formamidopyrimidine-DNA glycosylase (Fpg) and the mammalian XPA protein were applied. Both proteins were inhibited by Cd(II) and Cu(II). Hg(II) strongly inhibited the Fpg protein, but did not affect the XPA protein. In contrast, the XPA protein was disturbed by Co(II) and Ni(II), while the activity of the Fpg protein was not reduced. Neither protein was inhibited by As(III) or Pb(II). Thus, each zinc finger protein appears to have its own structural features and sensitivities towards Toxic Metal ions. Furthermore, each Metal exerts specific mechanisms leading to DNA repair inhibition.
