Free iron concentrations

Table XI lists a selection of log K and pM values for a range of iron(III) complexes (197), to illustrate the range of maximum free iron concentrations obtainable (down to pM — 32.6, i.e., less than 10 moldm for tris-hopo complexes) as well as the pM-Iog K...

Nitrilotriacetic acid (NTA) is a constituent of various domestic and hospital detergents and is a common water contaminant. NTA forms water-soluble chelate complexes with various metal ions, including iron, at neutral pH. Its iron complex, Fe-NTA, is a known potent nephrotoxic agent. The renal toxicity is assumed to be caused by the elevation of serum free-iron concentration following the reduction of Fe-NTA at the luminal side of the proximal tubule, which generates reactive oxygen species and leads to enhancement of lipid peroxidation. 

It is safe to say that Iron Blue is stable at a pH value of 7, i.e., in a neutral aqueous medium, so we take this as a minimum value. As mentioned earlier, a pH value of about 10 can be considered the upper limit of stability for Iron Blue, so we take this as maximum value for the following calculations. At pH=7, and even more so at pH=10, the free iron concentration is extremely low, since Fe(OH)3 is nearly insoluble (see Table 5). 

Fig. (7). Hypothetical consequences of NO-mediated inhibition of plant cytosolic aconitase [208]. The interaction between NO and cytosolic aconitase triggers a cluster dissassembly and subsequently the inhibition of the catalytic activity of the enzyme. By analogy to mammalian studies, the resulting apoprotein may act as iron regulatory protein (1RP) and may modulate the translation of mRNA encoding proteins involved in the cellular iron homeostasis. The elevated free iron concentration promotes the Fenton reaction leading to hydroxyl radical (HO ) production. Both HO- and high concentrations of iron create a killing environment for host and pathogen.

The free iron of plasma is essentially nondetectable. From the normal urinary excretion (30, 31), it is estimated that the free iron concentration in plasma could be about 0.1 /xg/100 ml or 0.02 /xM. It would be reasonable to consider that Fe(II) is oxidized to Fe(III) in plasma under... 

The gas is washed with water to remove any hydrogen chloride. Since iron(II) sulphide is a non-stoichiometric compound and always contains some free iron, the hydrogen sulphide always contains some hydrogen, liberated by the action of the iron on the acid. A sample of hydrogen sulphide of better purity can be obtained if antimony(III) sulphide, (stibnite) SbjSj, is warmed with concentrated hydrochloric acid ... 

The standard redox potential is 1.14 volts the formal potential is 1.06 volts in 1M hydrochloric acid solution. The colour change, however, occurs at about 1.12 volts, because the colour of the reduced form (deep red) is so much more intense than that of the oxidised form (pale blue). The indicator is of great value in the titration of iron(II) salts and other substances with cerium(IV) sulphate solutions. It is prepared by dissolving 1,10-phenanthroline hydrate (relative molecular mass= 198.1) in the calculated quantity of 0.02M acid-free iron(II) sulphate, and is therefore l,10-phenanthroline-iron(II) complex sulphate (known as ferroin). One drop is usually sufficient in a titration this is equivalent to less than 0.01 mL of 0.05 M oxidising agent, and hence the indicator blank is negligible at this or higher concentrations. 

Figure 15.17 The factors that influence the concentration of free iron in the cell. The two factors are the number of transferrin receptors in the plasma membrane and the concentration of apoferritin.

Iron absorption. Tea, administered by gastric intubation to rats, did not affect iron absorption when tea was consumed for 3 days but when delivered in tea the absorption was decreased. Rats maintained on a commercial diet were fasted overnight with free access to water and then gavaged with 1 mL of Fe labeled FeC13 (0.1 mM or 1 mM) and lactulose (0.5 M) in water or black tea. Iron absorption was estimated from Fe retention. Intestinal permeability was evaluated by lactulose excretion in the urine. Iron absorption was lower with given with tea at both iron concentrations but tea did not affect lactulose excretion "". ... 

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