Mössbauer and EPR detection of iron trafficking kinetics and possibly labile iron pools in whole Saccharomyces cerevisiae cells.

The kinetics of iron trafficking in whole respiring Saccharomyces cerevisiae cells were investigated using Mössbauer and EPR spectroscopies. The Mössbauer-active isotope Fe was added to cells growing under iron-limited conditions; cells were analyzed at different times post iron addition. Spectroscopic changes suggested that the added Fe initially entered the labile iron pool, and then distributed to vacuoles and mitochondria.

Yeast Mitochondria Import Aqueous Fe and, When Activated for Iron-Sulfur Cluster Assembly, Export or Release Low-Molecular-Mass Iron and Also Export Iron That Incorporates into Cytosolic Proteins.

Iron-sulfur cluster (ISC) assembly occurs in both mitochondria and cytosol. Mitochondria are thought to export a low-molecular-mass (LMM) iron and/or sulfur species which is used as a substrate for cytosolic ISC assembly. This species, called X-S or (Fe-S), has not been directly detected.

Labile Iron Pool of Isolated Cytosol Likely Includes Fe-ATP and Fe-Citrate but not Fe-Glutathione or Aqueous Fe.

The existence of labile iron pools (LFePs) in biological systems has been recognized for decades, but their chemical composition remains uncertain. Here, the LFeP in cytosol from was investigated. Mössbauer spectra of whole vs lysed cells indicated significant degradation of iron-sulfur clusters (ISCs), even using an unusually gentle lysis procedure; this demonstrated the fragility of ISCs.

Low-temperature Mössbauer spectroscopy of organs from Fe-enriched HFE hemochromatosis mice: an iron-dependent threshold for generating hemosiderin.

Hereditary hemochromatosis is an iron-overload disease most often arising from a mutation in the Homeostatic Fe regulator (HFE) gene. HFE organs become overloaded with iron which causes damage. Iron-overload is commonly detected by NMR imaging, but the spectroscopic technique is insensitive to diamagnetic iron.

Might nontransferrin-bound iron in blood plasma and sera be a nonproteinaceous high-molecular-mass Fe aggregate?

The HFE (Homeostatic Fe regulator) gene is commonly mutated in hereditary hemochromatosis. Blood of (HFE)(-/-) mice and of humans with hemochromatosis contains toxic nontransferrin-bound iron (NTBI) which accumulates in organs. However, the chemical composition of NTBI is uncertain.

Mössbauer-based molecular-level decomposition of the Saccharomyces cerevisiae ironome, and preliminary characterization of isolated nuclei.

One hundred proteins in Saccharomyces cerevisiae are known to contain iron. These proteins are found mainly in mitochondria, cytosol, nuclei, endoplasmic reticula, and vacuoles. Cells also contain non-proteinaceous low-molecular-mass labile iron pools (LFePs).

Cooperative redox and spin activity from three redox congeners of sulfur-bridged iron nitrosyl and nickel dithiolene complexes.

The synthesis of sulfur-bridged Fe-Ni heterobimetallics was inspired by Nature's strategies to "trick" abundant first row transition metals into enabling 2-electron processes: redox-active ligands (including pendant iron-sulfur clusters) and proximal metals. Our design to have redox-active ligands on each metal, NO on iron and dithiolene on nickel, resulted in the observation of unexpectedly intricate physical properties. The metallodithiolate, (NO)Fe(NS), reacts with a labile ligand derivative of [Ni(SCPh)], Ni, yielding the expected S-bridged neutral adduct, , containing a doublet {Fe(NO)}.

Yeast cells depleted of the frataxin homolog Yfh1 redistribute cellular iron: Studies using Mössbauer spectroscopy and mathematical modeling.

The neurodegenerative disease Friedreich's ataxia arises from a deficiency of frataxin, a protein that promotes iron-sulfur cluster (ISC) assembly in mitochondria. Here, primarily using Mössbauer spectroscopy, we investigated the iron content of a yeast strain in which expression of yeast frataxin homolog 1 (Yfh1), oxygenation conditions, iron concentrations, and metabolic modes were varied. We found that aerobic fermenting Yfh1-depleted cells grew slowly and accumulated Fe nanoparticles, unlike WT cells.

Influence of Metal Identity on Light-Induced Switchable Adsorption in Azobenzene-Based Metal-Organic Frameworks.

Energy-efficient capture and release of small gas molecules, particularly carbon dioxide (CO) and methane (CH), are of significant interest in academia and industry. Porous materials such as metal-organic frameworks (MOFs) have been extensively studied, as their ultrahigh porosities and tunability enable significant amounts of gas to be adsorbed while also allowing specific applications to be targeted. However, because of the microporous nature of MOFs, the gas adsorption performance is dominated by high uptake capacity at low pressures, limiting their application.

Thermal decarboxylation for the generation of hierarchical porosity in isostructural metal-organic frameworks containing open metal sites.

The effect of metal-cluster redox identity on the thermal decarboxylation of a series of isostructural metal-organic frameworks (MOFs) with tetracarboxylate-based ligands and trinuclear μ-oxo clusters was investigated. The PCN-250 series of MOFs can consist of various metal combinations (Fe, Fe/Ni, Fe/Mn, Fe/Co, Fe/Zn, Al, In, and Sc). The Fe-based system can undergo a thermally induced reductive decarboxylation, producing a mixed valence cluster with decarboxylated ligand fragments subsequently eliminated to form uniform mesopores.

The Pyrococcus furiosus ironome is dominated by [FeS] clusters or thioferrate-like iron depending on the availability of elemental sulfur.

Pyrococcus furiosus is a hyperthermophilic anaerobic archaeon whose metabolism depends on whether elemental sulfur is (+S) or is not (-S) included in growth medium. Under +S conditions, expression of respiratory hydrogenase declines while respiratory membrane-bound sulfane reductase and the putative iron-storage protein IssA increase. Our objective was to investigate the iron content of WT and ΔIssA cells under these growth conditions using Mössbauer spectroscopy.

Mössbauer and LC-ICP-MS investigation of iron trafficking between vacuoles and mitochondria in vma2ΔSaccharomyces cerevisiae.

Vacuoles are acidic organelles that store Fe polyphosphate, participate in iron homeostasis, and have been proposed to deliver iron to mitochondria for iron-sulfur cluster (ISC) and heme biosynthesis. Vma2Δ cells have dysfunctional V-ATPases, rendering their vacuoles nonacidic. These cells have mitochondria that are iron-dysregulated, suggesting disruption of a putative vacuole-to-mitochondria iron trafficking pathway.

The thermally induced decarboxylation mechanism of a mixed-oxidation state carboxylate-based iron metal-organic framework.

Investigations into a thermally generated decarboxylation mechanism for metal site activation and the generation of mesopores in a carboxylate iron-based MOF, PCN-250, have been conducted. PCN-250 exhibits an interesting oxidation state change during thermal treatment under inert atmospheres or vacuum conditions, transitioning from an Fe(iii) cluster to a Fe(ii)Fe(iii) cluster. To probe this redox event and discern a mechanism of activation, a combination of thermogravimetric analysis, gas sorption, scanning electron microscopy, Fe Mössbauer spectroscopy, gas chromatography-mass spectrometry, and X-ray diffraction studies were conducted.