scholarly journals Effect of temperature on liposome structures studied using EPR spectroscopy

2005 ◽  
Vol 19 (1) ◽  
pp. 37-42 ◽  
Author(s):  
W.W. Sulkowski ◽  
D. Pentak ◽  
W. Korus ◽  
A. Sulkowska
Keyword(s):  
Structural Changes ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Rotational Correlation Time ◽  
Effect Of Temperature ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Liposome Membrane ◽  
X Band ◽  
Increasing Temperature ◽  
Parameter Values

The effect of temperature on liposome structures has been investigated by means of electron paramagnetic resonance spectroscopy with the use of the spin labelling technique. The EPR spectra were recorded on a Bruker EMX spectrometer at the X band in the temperature range 300–340 K. Liposomes were prepared from L?a?phosphatidylcholine dipalmitoyl (1,2?dihexadecanoyl?sn?glycerol?3?phosphocholine) 99% (DPPC), DL?a?phosphatidylcholine dimyristoyl (1,2?ditetradecanoyl?rac?glycerol?3?phosphocholine) 99% (DMPC) and cholesterol (5?cholesten?3ß?ol) 99+% to constitute the membrane. The spin marker, 2?(3carboxypropyl)?4,4?dimethyl?2?tridecyl?3?oxazolidinyloxyl free radical (5?DOXYL), placed in a liposome membrane, allows for observation of structural changes in liposomes with temperature increase. The changes of rotational correlation time and order parameter values with increasing temperature result from the motion rise of the spin probe. The intensity of the EPR signal of 5?DOXYL gives us information about membrane fluidity.

scholarly journals Sub-3 Å resolution structure of 110 kDa nitrite reductase determined by 200 kV cryogenic electron microscopy

2020 ◽  
Author(s):  
Naruhiko Adachi ◽  
Takahide Yamaguchi ◽  
Toshio Moriya ◽  
Masato Kawasaki ◽  
Kotaro Koiwai ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Structural Changes ◽  
Catalytic Mechanism ◽  
Crystal Packing ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Data Bank ◽  
Comparison Method ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Map Comparison

AbstractCu-containing nitrite reductases (NiRs), a well-studied family of 110 kDa enzymes, play central roles in denitrification and have over 100 Protein Data Bank entries. However, such issues as crystal packing, photoreduction, and lack of high pH cases have impeded structural analysis of the catalytic mechanism. Here we show the cryogenic electron microscopy (cryo-EM) structures of Achromobacter cycloclastes NiR (AcNiR) at 2.99 and 2.85 Å resolution with pH 6.2 and 8.1, respectively. Comprehensive comparisons with cryo-EM and 56 AcNiR crystal structures suggested crystallographic artifacts in residues 185–215 and His255 due to packing and photoreduction, respectively. With electron paramagnetic resonance spectroscopy, a newly developed map comparison method supported local structural changes at pH 8.1 around the type-2 Cu site, including His255 deprotonation. While the theoretical coordination error estimation of cryo-EM structures remains difficult, combined analysis using X-ray and cryo-EM structures will allow deeper insight into the local structural changes of proteins.

Paramagnetic Ge–Li centres in alpha quartz revisited: The DLi([GeO4/Li]0D) centre

2008 ◽  
Vol 86 (11) ◽  
pp. 1303-1311
Author(s):  
R F.C. Claridge ◽  
O M Kryliouk ◽  
J A Weil ◽  
J A.S. Williams
Keyword(s):  
Electron Paramagnetic Resonance Spectroscopy ◽  
Spin Hamiltonian Parameter ◽  
Resonance Spectroscopy ◽  
Paramagnetic Defect ◽  
Paramagnetic Resonance ◽  
Hamiltonian Parameter ◽  
X Band ◽  
X Irradiation ◽  
And Storage ◽  
Electron Paramagnetic

A previously unreported stable paramagnetic defect centre in single-crystal alpha-quartz has been studied by quantitative X-band electron paramagnetic resonance spectroscopy at 15, 100, and 296 K, and is shown to contain a Ge3+ ion, presumably located substitutional for Si4+, with a nearby interstitial Li+ ion. The centre, called DLi herein, grows in slowly (months) after room-temperature x-irradiation and storage. Hyperfine structure arising from 73Ge, 7Li, and 29Si has been observed. The spin-Hamiltonian parameter matrices g, A(7Li), A(73Ge), and P(73Ge) are reported, also for centre CLi. A thermal dynamic process, probably involving Li+ hopping, begins to be appreciable above 100 K. Discussion of DLi, its apparent growth from another paramagnetic centre (not yet fully characterized), and comparison with other similar defects is included.PACS Nos.: 42.70.Ce, 61.72.Hh, 61.72–y, 61.72S–, 61.72uf, 61.80–x, 76.30–v, 76.30.Mi

scholarly journals Tauroursodeoxycholic Acid (TUDCA)—Lipid Interactions and Antioxidant Properties of TUDCA Studied in Model of Photoreceptor Membranes

Membranes ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 327
Author(s):  
Michał J. Sabat ◽  
Anna M. Wiśniewska-Becker ◽  
Michał Markiewicz ◽  
Katarzyna M. Marzec ◽  
Jakub Dybas ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Plasma Membranes ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Protective Action ◽  
Antioxidant Properties ◽  
Model Membranes ◽  
Dynamics Simulation ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Tauroursodeoxycholic Acid

Tauroursodeoxycholic acid (TUDCA), a hydrophilic bile acid containing taurine conjugated with the ursodeoxycholic acid (UDCA), has been known and used from ancient times as a therapeutic compound in traditional Chinese medicine. TUDCA has recently been gaining significant interest as a neuroprotective agent, also exploited in the visual disorders. Among several mechanisms of TUDCA’s protective action, its antioxidant activity and stabilizing effect on mitochondrial and plasma membranes are considered. In this work we investigated antioxidant activity of TUDCA and its impact on structural properties of model membranes of different composition using electron paramagnetic resonance spectroscopy and the spin labeling technique. Localization of TUDCA molecules in a pure POPC bilayer has been studied using a molecular dynamics simulation (MD). The obtained results indicate that TUDCA is not an efficient singlet oxygen (1O2 (1Δg)) quencher, and the determined rate constant of its interaction with 1O2 (1Δg) is only 1.9 × 105 M−1s−1. However, in lipid oxidation process induced by a Fenton reaction, TUDCA reveals substantial antioxidant activity significantly decreasing the rate of oxygen consumption in the system studied. In addition, TUDCA induces slight, but noticeable changes in the polarity and fluidity of the investigated model membranes. The results of performed MD simulation correspond very well with the experimental results.

scholarly journals Ambient base-free glycerol oxidation over bimetallic PdFe/SiO2 by in situ generated active oxygen species

2021 ◽  
Author(s):  
Ricci Underhill ◽  
Mark Douthwaite ◽  
Richard J. Lewis ◽  
Peter J. Miedziak ◽  
Robert D. Armstrong ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Bimetallic Catalyst ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Active Oxygen Species ◽  
Catalytic Performance ◽  
Resonance Spectroscopy ◽  
Oxygen Species ◽  
Paramagnetic Resonance ◽  
Temperature Oxidation

AbstractLow temperature oxidation of alcohols over heterogeneous catalysts is exceptionally challenging, particularly under neutral conditions. Herein, we report on an efficient, base-free method to oxidise glycerol over a 0.5%Pd-0.5%Fe/SiO2 catalyst at ambient temperature in the presence of gaseous H2 and O2. The exceptional catalytic performance was attributed to the in situ formation of highly reactive surface-bound oxygenated species, which promote the dehydrogenation on the alcohol. The PdFe bimetallic catalyst was determined to be significantly more active than corresponding monometallic analogues, highlighting the important role both metals have in this oxidative transformation. Fe leaching was confirmed to occur over the course of the reaction but sequestering experiments, involving the addition of bare carbon to the reactions, confirmed that the reaction was predominantly heterogeneous in nature. Investigations with electron paramagnetic resonance spectroscopy suggested that the reactivity in the early stages was mediated by surface-bound reactive oxygen species; no homogeneous radical species were observed in solution. This theory was further evidenced by a direct H2O2 synthesis study, which confirmed that the presence of Fe in the bimetallic catalyst neither improved the synthesis of H2O2 nor promoted its decomposition over the PdFe/SiO2 catalyst.

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