Effect Of Iron Concentrations Research Articles

Effect of iron concentrations on the DNA-degradation reaction by bleomycin

DNA-degradation reaction by bleomycin was conducted with form I of SV40 DNA as the substrate under "iron-limited conditions" and "iron-sufficient conditions". For "iron-limited conditions", the iron ions in reaction mixtures were derived from contaminant iron in the bleomycin preparation, the molar ratio of bleomycin/iron being 1/0.05. For "iron-sufficient conditions", Fe(II) was added to reaction mixtures to attain the molar ratio of bleomycin/iron at 1/1 to 1/29. DNA-degradation reaction by Fe(II) without bleomycin, or "Fe(II) alone", was also run for comparison. In any case, the reaction was allowed to proceed at such low rates that other products than form II and form III, due to further fragmentation, were negligible. The mass of DNA in each form was quantitatively determined by spectrofluorometry after agarose gel electrophoresis and staining with ethidium bromide. "Iron-limited conditions" and "iron-sufficient conditions" showed similar reaction characteristics as follows. As form I decreased with incubation time, form II increased faster than form III, hit a plateau (ca. 65% of total DNA) and decreased gradually thereafter. Form III kept increasing throughout the incubation. The reaction was dependent on incubation time and on doses of both bleomycin and Fe(II) but rather independent of temperature. The reaction was inhibited by acidic pH, Tiron (a specific chelator of iron) and Cu(II) but not EDTA. Octanucleotides with specific base sequence inhibited the reaction. DNA-degradation reaction by "Fe(II) alone" showed different characteristics as follows. The reaction proceeded rapidly at first, but ceased within 2 minutes. The extent of reaction was dependent on dose of Fe(II). The reaction product was form II accompanied by little amount of form III. The reaction was highly dependent on temperature, inhibited by EDTA, and not inhibited by Cu(II) and acidic pH. Octanucleotides, irrespective of their base sequences, inhibited the reaction.

Effects of iron concentrations on the electrical properties of La0.67Ba0.33Mn1−xFexO3

• Introducing iron in LBMO system decreases electrical conductance. • The material turns from metallic into semi-insulating behavior when increasing Fe concentration. • The value x = 0.10 represents the limit of Fe concentrations which destroys metallic-insulating transition. • Under polarization, the conductance of the material increases and activation energy decreases for all Fe concentrations. In order to study the electrical properties of the samples La 0.67 Ba 0.33 Mn 1− x Fe x O 3 , transport measurements have been performed on this compound using admittance spectroscopy technique. For all temperatures the DC conductance decreases when increasing Fe content and x = 0.10 represents the limit value of Fe concentration which destroys metallic-insulating transition. From DC conductance study, electronic conduction is found to be dominated by thermally activated hopping. Activation energy is deduced from the variation of conductance with temperature. This energy increases with increasing Fe content from E a = 27 meV for x = 0 to E a = 154 meV for x = 0.20. The AC conductance spectrum is found to obey Jonscher universal power law. The exponent “ n ” changes with Fe concentration ( n ≈ 1 for x = 0.20 and n = 0 for x = 0). This indicates that the material evolves from metallic to semi-insulating behavior when increasing Fe content. Under polarization, the conductance of the material increases and activation energy decreases for all Fe concentrations.

Effects of Iron Concentrations, Filter Hydraulic Loading Rates, and Porosities on Iron Removal by Rapid Sand Filtration

Oxidation of iron particles occurring as a result of oxidation of ferrous iron Fe(II) result in undesirable effects in water quality. These iron particles can be removed from water through physical treatment processes of filtration, adsorption, and membrane systems. Iron removal with a rapid sand filtration method was investigated. Effects of iron concentrations, filter hydraulic loading rates, and porosities were studied for the effluent iron concentration, turbidity, and head loss parameters. Plexiglas filter column system with an inner diameter of 30 mm and an equivalent diameter of silica sand with 0.59 mm was used. Four iron concentrations and four hydraulic loading rates were applied. Effects of filter hydraulic loading rates depend on the influent iron concentrations. Low iron concentrations could be removed by rapid sand filtration without high head loss occurrences. Moreover, effluent iron concentrations obtained for this situation were found to be lower than 0.2 mg/L, which is the legislative limit of Turkish Drinking Water Regulation (TDWR). Filter operation time increased with increasing the porosity. Filter operation time was about 2.4 times higher at the porosity of 0.40 than that at the porosity value of 0.36. Low effluent iron concentrations were obtained at the porosity value of 0.36.

Effect of iron concentration on toxin production in Campylobacter jejuni and Campylobacter coli.

The effect of iron concentrations in culture media on supernatant yields of campylobacter cytotonic toxin (CCT) was studied. Of the 118 Campylobacter spp. strains surveyed, 78.8% produced toxin in brucella broth or in casamino acids--yeast extract (CYE) broth. When the iron concentration of CYE was increased from 0.44 microgram/mL (7.9 microM) to 0.65 microgram/mL (11.6 microM) by the addition of ferric chloride, 94.9% of the strains were positive for toxin in a ganglioside GM1 based, enzyme-linked immunosorbent assay, using antibody to affinity-purified CCT. The addition of iron as ferrous sulfate was less effective. When four toxin-positive strains were grown in a deferrated medium of conalbumin-treated CYE with 0.04-0.08 microgram iron/mL (0.72-1.43 microM), two of the culture supernatants became negative (absorbance at 410 nm, less than 0.1 and less than 10 ng CCT/mL), and two produced about 90% less CCT but were still classified as positive (absorbance, greater than or equal to 0.1 and greater than or equal to 10 ng CCT/mL). It was therefore concluded that the production of CCT by Campylobacter spp. is influenced by iron concentration.