The hydrogenase from Desulfovibrio baculatus (DSM 1743) was purified from each of three different fractions: soluble periplasmic (wash), soluble cytoplasmic (cell disruption) and membrane-bound (detergent solubilization). Plasma-emission metal analysis detected in all three fractions the presence of iron plus nickel and selenium in equimolecular amounts. These hydrogenases were shown to be composed of two non-identical subunits and were distinct with respect to their spectroscopic properties. The EPR spectra of the native (as isolated) enzymes showed very weak isotropic signals centered around g approximately 2.0 when observed at low temperature (below 20 K). The periplasmic and membrane-bound enzymes also presented additional EPR signals, observable up to 77 K, with g greater than 2.0 and assigned to nickel(III). The periplasmic hydrogenase exhibited EPR features at 2.20, 2.06 and 2.0. The signals observed in the membrane-bound preparations could be decomposed into two sets with g at 2.34, 2.16 and approximately 2.0 (component I) and at 2.33, 2.24, and approximately 2.0 (component II). In the reduced state, after exposure to an H2 atmosphere, all the hydrogenase fractions gave identical EPR spectra. EPR studies, performed at different temperatures and microwave powers, and in samples partially and fully reduced (under hydrogen or dithionite), allowed the identification of two different iron-sulfur centers: center I (2.03, 1.89 and 1.86) detectable below 10 K, and center II (2.06, 1.95 and 1.88) which was easily saturated at low temperatures. Additional EPR signals due to transient nickel species were detected with g greater than 2.0, and a rhombic EPR signal at 77 K developed at g 2.20, 2.16 and 2.0. This EPR signal is reminiscent of the Ni-signal C (g at 2.19, 2.14 and 2.02) observed in intermediate redox states of the well characterized Desulfovibrio gigas hydrogenase (Teixeira et al. (1985) J. Biol. Chem. 260, 8942]. During the course of a redox titration at pH 7.6 using H2 gas as reductant, this signal attained a maximal intensity around -320 mV. Low-temperature studies of samples at redox states where this rhombic signal develops (10 K or lower) revealed the presence of a fast-relaxing complex EPR signal with g at 2.25, 2.22, 2.15, 2.12, 2.10 and broad components at higher field. The soluble hydrogenase fractions did not show a time-dependent activation but the membrane-bound form required such a step in order to express full activity.(ABSTRACT TRUNCATED AT 400 WORDS)
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FEBS Lett
January 2025
Institute of Pharmaceutical Science, King's College London, UK.
The mitochondrial outer membrane iron-sulphur ([Fe-S]) protein mitoNEET has been extensively studied as a target of the anti-inflammatory and type-2 diabetes drug pioglitazone and as a protein affecting mitochondrial respiratory rate. Despite these extensive past studies, its molecular function has yet to be discovered. Here, we applied an interdisciplinary approach and discovered an explicit nitric oxide (NO) access site to the mitoNEET [2Fe-2S] cluster.
View Article and Find Full Text PDFInt J Biol Macromol
December 2024
Department of Chemistry, University of Ulsan, Ulsan 44610, Republic of Korea. Electronic address:
The improper handling and uncontrolled discharge of toxic organic dyes result in significant adverse effects on both human health and the environment. This study investigates the fabrication of SnO₂, yttrium and cobalt dual-doped SnO₂ (YCSn), chitosan-capped SnO₂ (CS*Sn), and chitosan-capped yttrium and cobalt dual-doped SnO₂ (CS*YCSn) nanoparticles using a one-step coprecipitation method for the photocatalytic degradation of methylene blue (MB) under visible light irradiation. Characterization techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), and ultraviolet-visible (UV-Vis) spectrophotometry confirm the successful synthesis of biodegradable CS*YCSn nanoparticles.
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December 2024
Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Fontenay-aux-Roses, France.
This paper presents the results of the first intercomparison exercise on Electron Paramagnetic Resonance (EPR) dosimetry using sorbitol, where the performance parameters of sorbitol as dosimetric material were evaluated by three independent participants. Each participant was asked to determine a calibration curve using a set of sorbitol powder samples irradiated to four different doses (1.00, 2.
View Article and Find Full Text PDFSci Adv
December 2024
Laboratoire des Biomolécules, LBM, Département de Chimie, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France.
Dynamic nuclear polarization (DNP) enhances nuclear magnetic resonance (NMR) sensitivity by transferring polarization from unpaired electrons to nuclei, but nearby nuclear spins are difficult to detect or "hidden" due to strong electron-nuclear couplings that hypershift their NMR resonances. Here, we detect these hypershifted spins in a frozen glycerol-water mixture doped with TEMPOL at ~1.4 K using spin diffusion enhanced saturation transfer (SPIDEST), which indirectly reveals their spectrum.
View Article and Find Full Text PDFMol Imaging Biol
December 2024
Oxygen Measurement Core, O2M Technologies, Chicago, IL, 60612, USA.
Purpose: Type 1 diabetes (T1D) is an autoimmune disease that leads to the loss of insulin-producing pancreatic beta cells. Beta cell replacement devices or bioartificial pancreas (BAP) have shown promise in curing T1D and providing long-term insulin independence without the need for immunosuppressants. Hypoxia in BAP devices damages cells and imposes limitations on device dimensions.
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