scholarly journals Sclerotia of the acellular (true) slime mould Fuligo septica as a model to study melanization and anabiosis

2008 ◽  
Vol 13 (1) ◽  
Author(s):  
Anna Krzywda ◽  
Elżbieta Petelenz ◽  
Dominika Michalczyk ◽  
Przemysław Płonka
Keyword(s):  
Water Balance ◽  
Model System ◽  
Paramagnetic Resonance ◽  
Slime Moulds ◽  
Oat Flour ◽  
Technical Simplicity ◽  
Electron Paramagnetic ◽  
Convenient Model

AbstractAcellular (true) slime moulds (Myxomycetes) are capable of a transition to the stage of sclerotium — a dormant form of plasmodium produced under unfavourable environmental conditions. In this study, sclerotia of Fuligo septica were analyzed by means of electron paramagnetic resonance (EPR) spectroscopy. The moulds were cultivated in vitro on filter paper, fed with oat flour, and kept until the plasmodia began to produce sclerotia. The obtained sclerotia differed in colour from yellow through orange to dark-brown. The EPR spectra revealed a free radical, melanin-like signal correlated with the depth of the colour; it was strongest in the dark sclerotia. Sclerotization only took place when the plasmodia were starved and very slowly dried. Only the yellow sclerotia were able to regenerate into viable plasmodia. This suggests that myxomycete cytoplasm dehydration is an active process regulated metabolically. Plasmodial sclerotization may therefore serve as a convenient model system to study the regulation of cytoplasmatic water balance, and sclerotia as a convenient material for EPR measurements, combining the quality of plasmodia with the technical simplicity of the measurements characteristic of dry spores. Darkening of the sclerotia is most probably a pathological phenomenon connected with the impairment of water balance during sclerotization.

ДИНИТРОЗИЛЬНЫЕ КОМПЛЕКСЫ ЖЕЛЕЗА C ТИОЛСОДЕРЖАЩИМИ ЛИГАНДАМИ ПРЕДСТАВЛЕНЫ В ЖИВЫХ ОРГАНИЗМАХ В ОСНОВНОМ ИХ БИЯДЕРНОЙ ФОРМОЙ

2020 ◽  
Vol 65 (6) ◽  
pp. 1142-1153
Author(s):  
В.Д. Микоян ◽  
◽  
Е.Н. Бургова ◽  
Р.Р. Бородулин ◽  
А.Ф. Ванин ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Sodium Nitrite ◽  
Iron Complexes ◽  
Paramagnetic Resonance ◽  
First Case ◽  
Dinitrosyl Iron ◽  
Electron Paramagnetic ◽  
Dinitrosyl Complexes

The number of mononitrosyl iron complexes with diethyldithiocarbamate, formed in the liver of mice in vivo and in vitro after intraperitoneal injection of binuclear dinitrosyl iron complexes with N-acetyl-L-cysteine or glutathione, S-nitrosoglutathione, sodium nitrite or the vasodilating drug Isoket® was assessed by electron paramagnetic resonance (EPR). The number of the said complexes, in contrast to the complexes, formed after nitrite or Isoket administration, the level of which sharply increased after treatment of liver preparations with a strong reducing agent - dithionite, did not change in the presence of dithionite. It was concluded that, in the first case, EPR-detectable mononitrosyl iron complexes with diethyldithiocarbamate in the absence and presence of dithionite appeared as a result of the reaction of NO formed from nitrite with Fe2+-dieth- yldithiocarbamate and Fe3+-diethyldithiocarbamate complexes, respectively. In the second case, mononitrosyl iron complexes with diethyldithiocarbamate appeared as a result of the transition of iron-mononitosyl fragments from ready-made iron-dinitrosyl groups of binuclear dinitrosyl complexes, which is three to four times higher than the content of the mononuclear form of these complexes in the tissue...

scholarly journals The binuclear cluster of [FeFe] hydrogenase is formed with sulfur donated by cysteine of an [Fe(Cys)(CO)2(CN)] organometallic precursor

2019 ◽  
Vol 116 (42) ◽  
pp. 20850-20855 ◽  
Author(s):  
Guodong Rao ◽  
Scott A. Pattenaude ◽  
Katherine Alwan ◽  
Ninian J. Blackburn ◽  
R. David Britt ◽  
...  
Keyword(s):  
Double Resonance ◽  
Electron Nuclear Double Resonance ◽  
Paramagnetic Resonance ◽  
Carbon And Nitrogen ◽  
Binuclear Cluster ◽  
Organometallic Precursor ◽  
Pulse Epr ◽  
X Ray Absorption ◽  
Electron Paramagnetic

The enzyme [FeFe]-hydrogenase (HydA1) contains a unique 6-iron cofactor, the H-cluster, that has unusual ligands to an Fe–Fe binuclear subcluster: CN−, CO, and an azadithiolate (adt) ligand that provides 2 S bridges between the 2 Fe atoms. In cells, the H-cluster is assembled by a collection of 3 maturases: HydE and HydF, whose roles aren’t fully understood, and HydG, which has been shown to construct a [Fe(Cys)(CO)2(CN)] organometallic precursor to the binuclear cluster. Here, we report the in vitro assembly of the H-cluster in the absence of HydG, which is functionally replaced by adding a synthetic [Fe(Cys)(CO)2(CN)] carrier in the maturation reaction. The synthetic carrier and the HydG-generated analog exhibit similar infrared spectra. The carrier allows HydG-free maturation to HydA1, whose activity matches that of the native enzyme. Maturation with 13CN-containing carrier affords 13CN-labeled enzyme as verified by electron paramagnetic resonance (EPR)/electron nuclear double-resonance spectra. This synthetic surrogate approach complements existing biochemical strategies and greatly facilitates the understanding of pathways involved in the assembly of the H-cluster. As an immediate demonstration, we clarify that Cys is not the source of the carbon and nitrogen atoms in the adt ligand using pulse EPR to target the magnetic couplings introduced via a 13C3,15N-Cys–labeled synthetic carrier. Parallel mass-spectrometry experiments show that the Cys backbone is converted to pyruvate, consistent with a cysteine role in donating S in forming the adt bridge. This mechanistic scenario is confirmed via maturation with a seleno-Cys carrier to form HydA1–Se, where the incorporation of Se was characterized by extended X-ray absorption fine structure spectroscopy.

Sources and implications of basal nitric oxide in spontaneous contractions of guinea pig taenia caeci

2003 ◽  
Vol 285 (4) ◽  
pp. G747-G753 ◽  
Author(s):  
Catalina Caballero-Alomar ◽  
Carmen Santos ◽  
Diego Lopez ◽  
M. Teresa Mitjavila ◽  
Pere Puig-Parellada
Keyword(s):  
Nitric Oxide ◽  
Guinea Pig ◽  
Inhibitory Effect ◽  
No Production ◽  
Paramagnetic Resonance ◽  
Synthase Inhibitor ◽  
Spontaneous Contractions ◽  
Electron Paramagnetic

We examined in vitro the source and role of basal nitric oxide (NO) in proximal segments of guinea pig taenia caeci in nonadrenergic, noncholinergic (NANC) conditions. Using electron paramagnetic resonance (EPR), we measured the effect of the NO synthase inhibitor NG-nitro-l-arginine methyl ester (l-NAME, 10–4 M), the neuronal blocker tetrodotoxin (TTX, 10–6 M), or both on spontaneous contractions and on the production of basal NO. Both l-NAME and TTX, when tested alone, increased the amplitude and frequency of contractions. NO production was abolished by l-NAME and was inhibited by 38% by TTX. When tested together, l-NAME in the presence of TTX or TTX in the presence of l-NAME had no further effect on the amplitude or frequency of spontaneous contractions, and the NO production was inhibited. These findings suggest that basal NO consists of TTX-sensitive and TTX-resistant components. The TTX-sensitive NO has an inhibitory effect on spontaneous contractions; the role of TTX-resistant NO is unknown.

Quality of Bulk CdTe Substrates and its Relation to Intrinsic Defects

1994 ◽  
Vol 299 ◽  
Author(s):  
B. K. Meyer ◽  
D. M. Hofmann ◽  
W. Stadler ◽  
P. Emanuelsson ◽  
P. Omling ◽  
...  
Keyword(s):  
Negative Charge ◽  
Acceptor Level ◽  
Dangling Bond ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Teller Distortion ◽  
Jahn Teller ◽  
Electron Paramagnetic ◽  
Jahn Teller Distortion

AbstractBoth the cadmium vacancy (Vcd) and the tellurium vacancy (VTe) in CdTe are identified by means of electron paramagnetic resonance (EPR). The Vcd is a double acceptor and the EPR spectrum is observed in its single negative charge state. The symmetry is found to be trigonal, which can be explained in a model in which the hole occupies a dangling bond t2 orbital and the orbital degeneracy is removed by a static Jahn-Teller distortion. The hyperfine interaction shows that the hole is localised on one of the four Te neighbours. The EPR spectrum of VTe+ reveals cubic (unperturbed) symmetry and the hyperfine structure shows that the unpaired electron is equally spread over the four Cd neighboursPhoto-EPR measurements locate the 0/+ state of VTe at Ev + 0.2 eV and the 2-/- acceptor level of VCd to be situated less than 0.47 eV above the valence band.

scholarly journals Assessing dimerisation degree and cooperativity in a biomimetic small-molecule model by pulsed EPR

2015 ◽  
Vol 51 (25) ◽  
pp. 5257-5260 ◽  
Author(s):  
K. Ackermann ◽  
A. Giannoulis ◽  
D. B. Cordes ◽  
A. M. Z. Slawin ◽  
B. E. Bode
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Complex Formation ◽  
Small Molecule ◽  
Epr Spectroscopy ◽  
Model System ◽  
Paramagnetic Resonance ◽  
Pulsed Epr ◽  
Molecule Model ◽  
Pulsed Electron Paramagnetic Resonance ◽  
Electron Paramagnetic

Pulsed electron paramagnetic resonance (EPR) spectroscopy is used for titrating spin-labelled terpyridine with Zn(ii)-solution to study complex formation. This system can serve as a small-molecule model system for tuneable dimerisation.

scholarly journals [FeFe]-Hydrogenase Maturation: H-Cluster Assembly Intermediates Tracked by Electron Paramagnetic Resonance, Infrared, and X-Ray Absorption Spectroscopy

2020 ◽  
Author(s):  
Brigitta Németh ◽  
Moritz Senger ◽  
Holly J. Redman ◽  
Pierre Ceccaldi ◽  
Joan Broderick ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Absorption Spectroscopy ◽  
Cluster Assembly ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Hydrogenase Maturation ◽  
Catalytically Active ◽  
X Ray Absorption ◽  
Electron Paramagnetic

[FeFe]-hydrogenase enzymes employ a unique organometallic cofactor for efficient and reversible hydrogen conversion. This so-called H-cluster consists of a [4Fe-4S] cubane cysteine-linked to a diiron complex coordinated by carbon monoxide and cyanide ligands and an azadithiolate ligand (adt = NH(CH2S)2). [FeFe]-hydrogenase apo-protein binding only the [4Fe-4S] sub-complex can be fully activated in vitro by the addition of a synthetic diiron site precursor complex ([2Fe]adt,). Elucidation of the mechanism of cofactor assembly will aid in the design of improved hydrogen processing synthetic catalysts. We combined in situ electron paramagnetic resonance, Fourier-transform infrared, and X-ray absorption spectroscopy to characterize intermediates of H-cluster assembly as initiated by mixing of the apo-protein (HydA1) from the green alga Chlamydomonas reinhardtii with [2Fe]adt. The three methods consistently show rapid formation of a complete H-cluster in the oxidized, CO-inhibited state (Hox-CO) already within seconds after the mixing. Moreover, FTIR spectroscopy support a model in which Hox-CO formation is preceded by a short-lived Hred´-CO like intermediate. Accumulation of Hox-CO was followed by CO release resulting in the slower conversion to the catalytically active state (Hox) as well as formation of reduced states of the H-cluster.

Changes in free radical profiles during the callogenesis of responsive and recalcitrant potato genotypes

1994 ◽  
Vol 102 ◽  
pp. 243-246 ◽  
Author(s):  
E. Bailey ◽  
N. Deighton ◽  
S. A. Clulow ◽  
B. A. Goodman ◽  
E. E. Benson
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Plant Tissue ◽  
Direct Evidence ◽  
Paramagnetic Resonance ◽  
Biochemical Basis ◽  
Plant Tissue Cultures ◽  
Electron Paramagnetic ◽  
Free Radical Activity

Changes of the in vitro morphogenetic state may be achieved for some potato genotypes, but others are unresponsive (recalcitrant). Although the biochemical basis for somatic recalcitrance is unknown, evidence suggests that two different aspects of oxidative stress may be involved. Phenolic oxidation is a major problem in manipulating cultures of woody plant species (Thorpe & Harry 1990) and lipid peroxidation has been associated with recalcitrance in monocotyledonous plants (Cutler et al. 1989; Benson et al. 1992). Both oxidative phenomena are believed to be free-radical mediated, but to date there is no reported direct evidence for the formation of free radicals during plant tissue culture callogenesis. The objectives of the present study were twofold; to assess the feasibility of using electron paramagnetic resonance (EPR) spectroscopy to detect free radicals directly in plant tissue cultures and to investigate free radical activity during dedifferentiation of responsive and unresponsive potato genotypes.

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