Critical Stability Constants

Smith, Robert M.; Martell, Arthur E.

doi:10.1007/978-1-4757-5506-0

Cited by 1,323 publications

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“…1) (although this inhibition, in the presence of phosphate, could be due to the formation of the CoHPO 4 complex [10]), each step involved in ATP synthesis was analyzed separately, in order to identify the step that requires the lowest dose of Co 2+ needed to inhibit the ATP synthesis.…”

Section: Resultsmentioning

confidence: 99%

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The interactions of cobalt(II) with mitochondria from rat liver

et al. 2007

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The interactions of Co 2+ with mitochondria have been investigated. The results indicate that Co 2+ inhibits ATP synthesis. Further investigations into ATP synthesis mechanisms indicated that inhibition is due to the opening of a transmembrane pore. The opening of this pore causes the collapse of the high-energy intermediate where, under a pH and a potential gradient, the energy is stored and subsequently utilized to form ATP from ADP.

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Section: Resultsmentioning

confidence: 99%

“…The size of this pore allows the passage of large molecules [10,11]. If the mitochondria are resuspended in a sucrose medium, the opening of the pore allows the entry of sucrose.…”

Section: The Enhancement Of Membrane Permeabilitymentioning

confidence: 99%

The interactions of cobalt(II) with mitochondria from rat liver

et al. 2007

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“…When Ca 2ϩ or Mg 2ϩ was to be buffered simultaneously, five additional equilibria involving those cations were also considered. The respective equilibrium constants were taken from literature sources (26,27), and, when necessary, the Davies equation (28) was used to correct these to an ionic strength of 100 mM. The species distribution program COMICS (29) was used to solve the applicable sets of simultaneous equations at experimental conditions of interest and to allow the generation of standard curves.…”

Section: Methodsmentioning

confidence: 99%

Monensin Mediates a Rapid and Selective Transport of Pb2+

Hamidinia¹,

Shimelis²,

Tan³

et al. 2002

Journal of Biological Chemistry

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The carboxylic acid ionophore monensin, known as an electroneutral Na ؉ ionophore, an anticoccidial agent, and a growth-promoting feed additive in agriculture, is shown to be highly efficient as an ionophore for Pb 2؉ and to be highly selective for Pb 2؉ compared with other divalent cations. Monensin transports Pb 2؉ by an electroneutral mechanism in which the complex PbMonOH is the transporting species. Electrogenic transport via the species PbMon ؉ may also be possible. Monensin catalyzed Pb 2؉ transport is little affected by Ca 2؉ , Mg 2؉ , or K ؉ concentrations that are encountered in living systems. Na ؉ is inhibitory, but its effectiveness at 100 mM does not exceed ϳ50%. The poor activity of monensin as an ionophore for divalent cations other than Pb 2؉ is consistent with the pattern of complex formation constants observed in the mixed solvent 80% methanol/water. This pattern also explains why Ca 2؉ , Mg 2؉ , and K ؉ are ineffective as inhibitors of Pb 2؉ transport, but it does not fully explain the actions of Na ؉ , where kinetic features of the transport mechanism may also be important. When given to rats at 100 ppm in feed together with Pb 2؉ at 100 ppm in drinking water, monensin reduces Pb accumulation in several organs and tissues. It also accelerates the excretion of Pb that was accumulated previously and produces this effect without depleting the organs of zinc or copper. Monensin, used alone or in combination with other agents, may be useful for the treatment of Pb intoxication.

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“…The explanation is likely due to the inaccessibility of the Mn 3+ oxidation state in aqueous media at neutral pH owing to the large thermodynamic barrier which prevents Mn 2+ oxidation (standard reduction potential for Mn 3+ 1.2 V at pH 7 vs NHE). Moreover, divalent Mn 2+ with its spherical electronic distribution and half-filled 3d 5 electronic configuration forms relatively weak coordination complexes with all monodentate O, N, and S ligands [44]. Thus, free Mn 2+ does not generally associate tightly with the internal machinery of the cell unless there are pre-organized chelation sites present with multiple ligand donors.…”

Section: Intracellularmentioning

confidence: 99%

Photoassembly of the water-oxidizing complex in photosystem II

Dasgupta

Ananyev

Dismukes

2008

Coordination Chemistry Reviews

166

121

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The light-driven steps in the biogenesis and repair of the inorganic core comprising the O 2 -evolving center of oxygenic photosynthesis (photosystem II water-oxidation complex, PSII-WOC) are reviewed. These steps, known collectively as photoactivation, involve the photoassembly of the free inorganic cofactors to the cofactor-depleted PSII-(apo-WOC) driven by light and produce the active O 2 -evolving core comprised of Mn 4 CaO x Cl y . We focus on the functional role of the inorganic components as seen through the competition with non-native cofactors ("inorganic mutants") on water oxidation activity, the rate of the photoassembly reaction, and on structural insights gained from EPR spectroscopy of trapped intermediates formed in the initial steps of the assembly reaction. A chemical mechanism for the initial steps in photoactivation is given that is based on these data. Photoactivation experiments offer the powerful insights gained from replacement of the native cofactors, which together with the recent X-ray structural data for the resting holoenzyme provide a deeper understanding of the chemistry of water oxidation. We also review some new directions in research that photoactivation studies have inspired that look at the evolutionary history of this remarkable catalyst.

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Critical Stability Constants

Cited by 1,323 publications

References 0 publications

The interactions of cobalt(II) with mitochondria from rat liver

The interactions of cobalt(II) with mitochondria from rat liver

Monensin Mediates a Rapid and Selective Transport of Pb2+

Photoassembly of the water-oxidizing complex in photosystem II

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