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  • Articles  (5)
  • iron  (3)
  • Chemical evolution  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Pyrophosphate synthesis from phospho(enol)pyruvate catalyzed by precipitated magnesium phosphate with ”enzyme-like” activity (1992)
    Springer
    Journal of molecular evolution 35 (1992), S. 277-285 
    Details
    ISSN: 1432-1432
    Keywords: Transphosphorylation ; Pyrophosphate ; Precipitated magnesium phosphate ; Phospho(enol)pyruvate ; Phosphorolysis ; Chemical evolution ; Inorganic enzyme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The enzyme-like kinetic properties of precipitated magnesium phosphate as a catalyst for formation of pyrophosphate (PPi) from phospho (enol)pyruvate (PEP) are described. This synthesis occurs at a low temperature (37°C) and represents a model that may help us understand the relevance to chemical evolution of minerals as ancient catalysts whose functions could have been taken over by contemporary enzymes. An insoluble Pi.Mg matrix was formed in a medium with 80% of the water replaced by dimethyl sulfoxide as a way of simulating conditions in a drying pond. Phospho(enol)pyruvate adsorbs onto the Pi.Mg surface according to a Langmuir isotherm, and the PEP concentration dependence of PPi formation follows a Michaelian-like function. A yield of 33% for transformation of the initially adsorbed PEP into PPi was attained after 4 days of incubation with equimolecular concentrations of Pi, MgCl2, and PEP. The magnesium concentration dependence for Pi and Mg precipitation, for adsorption of PEP onto solid Pi.Mg, and for PPi formation showed complex cooperative behavior. These results taken as a whole lead to the conclusion that the Pi.Mg surface not only provides a reactant for PPi formation but also catalyzes the reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00161165
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  • 2
    Electronic Resource
    Electronic Resource
    Model for prebiotic pyrophosphate formation: Condensation of precipitated orthophosphate at low temperature in the absence of condensing or phosphorylating agents (1990)
    Springer
    Journal of molecular evolution 31 (1990), S. 353-358 
    Details
    ISSN: 1432-1432
    Keywords: Pyrophosphate formation ; Precipitated calcium phosphate ; Condensation reaction ; Chemical evolution ; Dimethyl sulfoxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The formation of pyrophosphate (PPi) by condensation of orthophosphate (Pi) at low temperature (37°C) in the absence of condensing or phosphorylating agents could have been an ancient process in chemical evolution. In the present investigation the synthesis of32PPi from32Pi was carried out at pH 8.0 and PPi was found in larger amounts in the presence of insoluble Pi (with calcium or manganese ions) than in its absence (with magnesium ions, or with no divalent cations present). After 10 days of incubation in the presence of precipitated calcium phosphate, about 1.6 nmol/ml of PPi was formed (0.057% yield relative to insoluble Pi). The hypothesis that the reaction is dependent on precipitated Pi was reinforced by the effect of adding dimethyl sulfoxide (2.1–9.9 M) in the presence of magnesium ions: the amount of magnesium phosphate precipitated in the presence of the organic solvent was proportional to the amount of PPi formed. The large and negative activation entropies found in aqueous media with calcium ions and in a medium containing 11.3 M dimethyl sulfoxide with magnesium ions suggest that the reaction was favored by a hydrophobic phenomenon at the surface of solid Pi. This reaction could serve as a model for prebiotic formation of PPi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02106049
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  • 3
    Electronic Resource
    Electronic Resource
    Role of Fe(III) in Fe(II)citrate-mediated peroxidation of mitochondrial membrane lipids (1999)
    Springer
    Molecular and cellular biochemistry 196 (1999), S. 163-168 
    Details
    ISSN: 1573-4919
    Keywords: Fe(II)citrate ; free radicals ; iron ; lipid peroxidation ; mitochondria ; reactive oxygen species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In this report we study the effect of Fe(III) on lipid peroxidation induced by Fe(II)citrate in mitochondrial membranes, as assessed by the production of thiobarbituric acid-reactive substances and antimycin A-insensitive oxygen uptake. The presence of Fe(III) stimulates initiation of lipid peroxidation when low citrate:Fe(II) ratios are used (≤ 4:1). For a citrate:total iron ratio of 1:1 the maximal stimulation of lipid peroxidation by Fe(III) was observed when the Fe(II):Fe(III) ratio was in the range of 1:1 to 1:2. The lag phase that accompanies oxygen uptake was greatly diminished by increasing concentrations of Fe(III) when the citrate:total iron ratio was 1:1, but not when this ratio was higher. It is concluded that the increase of lipid peroxidation by Fe(III) is observed only when low citrate:Fe(II) ratios were used. Similar results were obtained using ATP as a ligand of iron. Monitoring the rate of spontaneous Fe(II) oxidation by measuring oxygen uptake in buffered medium, in the absence of mitochondria, Fe(III)-stimulated oxygen consumption was observed only when a low citrate:Fe(II) ratio was used. This result suggests that Fe(III) may facilitate the initiation and/or propagation of lipid peroxidation by increasing the rate of Fe(II)citrate-generated reactive oxygen species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006988129221
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  • 4
    Electronic Resource
    Electronic Resource
    Characteristics of Fe(II)ATP complex-induced damage to the rat liver mitochondrial membrane (1995)
    Springer
    Molecular and cellular biochemistry 145 (1995), S. 53-60 
    Details
    ISSN: 1573-4919
    Keywords: mitochondria ; oxidative stress ; iron ; lipid peroxidation ; membrane permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract It is well established that several iron complexes can induce oxidative damage in hepatic mitochondrial membranes by catalyzing the formation of ·OH radicals and/or by promoting lipid peroxidation. This is a relevant process for the molecular basis of iron overload diseases. The present work demonstrates that Fe(II)ATP complexes (5–50μM) promote an oxygen consumption burst in a suspension of isolated rat liver mitochondria (either in the absence or presence of Antimycin A), caused mainly by lipid peroxidation. Fe(II)ATP alone induced small levels of oxygen uptake but no burst. The time course of Fe(II)ATP oxidation to Fe(III)ATP in the extramitochondrial media also reveals a simultaneous ‘burst phase’. The iron chelator Desferal (DFO) or the chain-break antioxidant butylated hydroxytoluene (BHT) fully prevented both lipid peroxidation (quantified as oxygen uptake burst) and mitochondrial swelling. DFO and BHT were capable of stopping the ongoing process of peroxidation at any point of their addition to the mitochondrial suspension. Conversely, DFO and BHT only halted the Fe(II)ATP-induced mitochondrial swelling at the onset of the process. Fe(II)ATP could also cause the collapse of mitochondrial potential, which was protected by BHT if added at the onset of the damaging process. These results, as well as correlation studies between peroxidation and mitochondrial swelling, suggest that a two phase process is occurring during Fe(II)ATP-induced mitochondrial damage: one dependent and another independent of lipid peroxidation. The involvement of lipid peroxidation in the overall process of mitochondrial membrane injury is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00925713
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  • 5
    Electronic Resource
    Electronic Resource
    Deoxyribose degradation catalyzed by Fe(III)-EDTA: kinetic aspects and potential usefulness for submicromolar iron measurements (1994)
    Springer
    Molecular and cellular biochemistry 137 (1994), S. 65-73 
    Details
    ISSN: 1573-4919
    Keywords: iron ; iron quantification ; deoxyribose degradation ; 2-deoxy-D-ribose ; thiobarbituric acid reactive substances ; hydroxyl radical ; superoxide radical ; copper
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Iron ions play a central role in ·OH radicals formation and induction of oxidative stress in living organisms. Ironcatalyzed ·OH radical formation degrades deoxyribose to thiobarbituric acid reactive substances (TBA-RS). This paper analyzes kinetic properties of the Fe(III)-EDTA-catalyzed deoxyribose degradation in the presence of ascorbate. The yield of TBA-RS formation in the presence of EDTA was 4-fold higher than in its absence, contrasting with results reported elsewhere, Cu(II)-EDTA and Fe(III)-citrate were unable to catalyze deoxyribose degradation. The dependence on deoxyribose concentration was fitted to a Lineweaver Burk-like plot and it was calculated that approximately 4.5 mM deoxyribose scavenged half of the ·OH radicals formed. The data for Fe(III)-EDTA concentration dependence could also be fitted to a rectangular hyperbolic function. This function was linear up to 1 μM added FeCl3 and this property could be utilized as an assay for the estimation of submicromolar iron concentrations. Submicromolar concentrations of iron could induce measurable yields of TBA-RS. Differences of as little as 0.1 μM Fe(III)-EDTA could be reproducibly detected under optimum experimental conditions, above a consistent background absorbance that was equivalent to 0.35±0.05 μM Fe(III)-EDTA and represented contaminating iron in the reactants that could not be removed with Chelex-100. The low method determination limit makes the deoxyribose degradation reaction potentially useful as a new, highly sensitive and cost effective assay for iron quantification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00926041
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