Iron-59, half-life

Indications Chronic iron overload due to blood transfusions Category Chelator, iron Half-life 8-16 hours... 

The Mossbauer effect, discovered by Rudolf L. Mossbauer in 1957, can in short be described as the recoil-free emission and resonant absorption of gamma radiation by nuclei. In the case of iron, the source consists of Co, which decays with a half-life of 270 days to an excited state of Fe (natural abundance in iron 2%). The latter, in turn, decays rapidly to the first excited state of this isotope. The final decay generates a 14.4 keV photon and a very narrow natural linewidth of the order of nano eV. 

A unique situation is encountered if Fe-M6ssbauer spectroscopy is applied for the study of spin-state transitions in iron complexes. The half-life of the excited state of the Fe nucleus involved in the Mossbauer experiment is tj/2 = 0.977 X 10 s which is related to the decay constant k by tj/2 = ln2/fe. The lifetime t = l//c is therefore = 1.410 x 10 s which value is just at the centre of the range estimated for the spin-state lifetime Tl = I/Zclh- Thus both the situations discussed above are expected to appear under suitable conditions in the Mossbauer spectra. The quantity of importance is here the nuclear Larmor precession frequency co . If the spin-state lifetime Tl = 1/feLH is long relative to the nuclear precession time l/co , i.e. Tl > l/o) , individual and sharp resonance lines for the two spin states are observed. On the other hand, if the spin-state lifetime is short and thus < l/o) , averaged spectra with intermediate values of quadrupole splitting A q and isomer shift 5 are found. For the intermediate case where Tl 1/cl , broadened and asymmetric resonance lines are obtained. These may be the subject of a lineshape analysis that will eventually produce values of rate constants for the dynamic spin-state inter-conversion process. The rate constants extracted from the spectra will be necessarily of the order of 10 -10 s"F... 

The metal is radioactive and does not occur in nature, as the half-life of all isotopes is shorter than 5 million years. It is found in readily isol-able amounts in nuclear reactors. It is an effective "rust-preventer" for iron and steel in special applications. The metastable isotope "Tc has a half-life of only 6 hours and is therefore used as a gamma radiator in medicine (radiation therapy and diagnostics). Of very little commercial importance. 

Iron homeostasis in mammalian cells is regulated by balancing iron uptake with intracellular storage and utilization. As we will see, this is largely achieved at the level of protein synthesis (translation of mRNA into protein) rather than at the level of transcription (mRNA synthesis), as was the case in microorganisms. This is certainly not unrelated to the fact that not only do microbial cells have a much shorter division time than mammalian cells, but that one consequence of this is that the half-life of microbial mRNAs is very much shorter (typically minutes rather than the hours or often days that we find with mammals). This makes it much easier to control levels of protein expression by changing the rate of specific mRNA synthesis by the use of inducers and repressors. So how do mammalian cells... 

We were quite elated, and it appeared that it was a rich field. Now, fifty years later, I must say that it wasn t as rich as we thought. But we have over the years discovered half a dozen natural radioactive elements, and two of these, the samarium-147 with its decay to neodymium-143 and rhenium-187 with its decay to osmium-187, prove to be of use in Nuclear Dating. The importance of rhenium is that it is iron soluble while the other radioactivities are insoluble in metallic iron. In fact, the best half life we have for rhenium-187 was obtained by measuring the osmium-187 to rhenium-187 ratio in iron meteorites which had been dated by other methods. This work was started many years ago by Dr. Herr and others in Germany. The half life is 43,000,000,000 years. 

Determine the decay constant for iron-55. The half-life of iron-55 is 2.7 years. 

Superoxide has a chemical half-life measured in microseconds, but in even this short time serious damage can be caused to all types of biological macromolecules. Peroxidation of membrane lipids could cause haemolysis but the oxidation of ferrous (Fe2+) to ferric (Fe3+) iron in haemoglobin due to free radical action is a more immediate cause for concern within the red cell (Figure 5.17). 

Chemical. Although no products were identified, p-chloronitrobenzene (1.5 x 10 M) was reduced by iron metal (33.3 g/L acid washed 18-20 mesh) in a carbonate buffer (1.5 x 10 M) at pH 5.9 and 15 °C. Based on the pseudo-first-order disappearance rate of 0.0336/min, the half-life was 20.6 min (Agrawal and Tratnyek, 1996). 

ISOTOPES There are 30 isotopes of iron ranging from Fe-45 to Fe-72. The following are the four stable isotopes with the percentage of their contribution to the elemenfs natural existence on Earth Fe-54 = 5.845%, Fe-56 = 91.72%, Fe-57 = 2.2%, and Fe-58 = 0.28%. It might be noted that Fe-54 is radioactive but is considered stable because it has such a long half-life (3.1 xlO years). The other isotopes are radioactive and are produced artificially. Their half-lives range from 150 nanoseconds to 1x10 years. 

Most of the chemical and physical properties of imniloctium (hassium) are unknown. What is known is that its most stable isotope (hassium-108) has the atomic weight (mass) of about 277. Hs-277 has a half-life of about 12 minutes, after which it decays into the isotope seaborgium-273 through either alpha decay or spontaneous fission. Hassium is the last element located at the bottom of group 8, and like element 107, it is produced by a cold fusion process that in hassium s case is accomplished by slamming iron (Fe-58) into particles of the isotope of lead (Pb-209), along with several neutrons, as follows ... 

Acrolein (CHj=CHCHO, also known as 2-propenal) is a a,P-unsaturated aldehyde that can be transformed reducfively to saturated or unsaturated alcohols by reduction of the C = 0 or C = C double bonds (Claus 1998). In addition, a,P-unsaturated aldehydes may undergo hydration reactions in aqueous solutions. It was observed that, under acidic (pH12) conditions, acrolein is hydrated to 3-hydroxypropanal (Jensen and Hashtroudi 1976). In a natural subsurface environment, where pH may range from 6.5 to 8.5, the hydration rate of acrolein increases with the pH and its half-life decreases. Based on an experiment to analyze effects of iron on acrolein transformation, Oh et al. (2006) note that, under acidic conditions (e.g., pH = 4.4), acrolein disappears rapidly from solution in the presence of elemental iron (Fig. 16.1). Moreover, the formation of... 

Cyclic voltammetry of iron(III) porphyrin-sulfate complexes has been described. Thiosulfate can add to iron(III) porphyrins to give an adduct which is high-spin at normal temperatures but low-spin at low temperatures. The tetraphenylporphyrin adduct undergoes decomposition slowly in DMF to give [Fe (tpp)] plus tetrathionate. In DMSO tetraphenylporphyrinatoiron(III) oxidizes thiosulfate by an autocatalytic process. Tetrathiotungstate complexes of iron(III)-tetra-phenylporphyrin undergo spontaneous reduction to iron(II) products with a half-life of about 30 minutes at ambient temperature. " ... 

The half-life of Fe2(OH)2" at room temperature is a few seconds. An improved model for the kinetics of dissociation of this dinuclear cation recognizes significan articipation by Fe2(OH)3 + at higher pHs, thus clearing up earlier slight anomalies in this area. Phosphate ester hydrolysis at the di-iron center of uteroferrin has now been shown to involve nucleophilic attack by bridging hydroxide (as proposed but not conclusively demonstrated for several M—OH—M-containing catalytic species) rather than by hydroxide bonded to just one Fe. ... 

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