Electron paramagnetic resonance spectroscopic study of nitroxide radicals formed from oximes

1969 ◽  
Vol 47 (12) ◽  
pp. 2227-2236 ◽  
Author(s):  
P. Smith ◽  
W. M. Fox
Keyword(s):  
Hydroxyl Radicals ◽  
Continuous Flow ◽  
Flow System ◽  
Functional Structure ◽  
Methyl Radicals ◽  
Paramagnetic Resonance ◽  
A Value ◽  
Butanedione Monoxime ◽  
Structure Formula ◽  
Electron Paramagnetic

The addition of hydroxyl radicals to each of the oximes, acetaldoxime, acetoxime, and 2,3-butanedione monoxime, has been studied by mixing titanous chloride, hydrogen peroxide, and the oxime in an aqueous continuous-flow system. In each case a β-hydroxy nitroxide (functional structure [Formula: see text] is formed. In confirmation of these results, amino and hydroxymethyl radicals were added to the oximes using similar procedures to give in each case the radicals of functional structure [Formula: see text] and [Formula: see text], respectively. Attempts to add methyl radicals, prepared by the reaction between titanous chloride and t-butyl hydroperoxide, to these oximes gave no observable products save the methyl radicals. However, use of titanous chloride and peracetic acid gave results consistent with the addition of hydroxyl radicals. The addition of hydroxyl radicals to the oxime-O-methyl ethers of acetaldehyde and acetone gave radicals of functional structure [Formula: see text][Formula: see text] which have not previously been identified unambiguously. On the assumption that |QN| = |QHNH| = 23 G in all these radicals, ρNπ has been calculated and used to obtain a value for [Formula: see text] of ca. 11 G which is within the range of other estimates in the literature.

On The EPR Parameters of Divalent Cobalt in ZnX (X = S, Se, Te) And CdTe

2004 ◽  
Vol 59 (12) ◽  
pp. 938-942 ◽  
Author(s):  
Shao-Yi Wu ◽  
Hui-Ning Dong
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Charge Transfer ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Paramagnetic Resonance ◽  
A Value ◽  
Epr Parameters ◽  
Divalent Cobalt ◽  
Structure Constants ◽  
Electron Paramagnetic

The electron paramagnetic resonance (EPR) parameters g and the hyperfine structure constants A of Co2+ in ZnX (X = S, Se, Te) and CdTe are studied, using the perturbation formulas of the EPR parameters for a 3d7 ion in tetrahedra based on two mechanism models. In these formulas, both the contributions from the conventional crystal-field (CF) mechanism and those from the charge-transfer (CT) mechanism are taken into account. According to the investigations, the sign of the g-shift ΔgCT from the CT mechanism is the same as ΔgCF from the CF mechanism, whereas the contributions to the A value from the CF and CT mechanisms have opposite signs. Particularly, the contributions to the EPR parameters from the CT mechanism increase rapidly with increase of the spin-orbit coupling coefficient of the ligand and the covalency effect of the systems, i. e. S2− < Se2− < Te2−.

An EPR/ENDOR study of aminoxyls (nitroxides) capable of intramolecular bonding: hydroxyalkyl radical spin adducts of nitrones

1988 ◽  
Vol 66 (8) ◽  
pp. 1901-1911 ◽  
Author(s):  
D. Larry Haire ◽  
Yashige Kotake ◽  
Edward G. Janzen
Keyword(s):  
Hydroxyl Radicals ◽  
Spectroscopic Method ◽  
Paramagnetic Resonance ◽  
Endor Spectroscopy ◽  
Hydroxyalkyl Radical ◽  
Close Proximity ◽  
Carbon Centered Radical ◽  
Intramolecular Bonding ◽  
Hyperfine Splittings ◽  
Electron Paramagnetic

A comparison of the effect of solvent and 13C labeling (of the radical addend) on the EPR (electron paramagnetic resonance) spectra of hydroxyalkyl vs. alkyl radical adducts of α-phenyl-N-tert-butyl nitrone (PBN) and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) has been investigated. The solution ENDOR spectra in toluene and in ethanol are the first examples studied of aminoxyls with hydroxyl substituents in close proximity to the free radical centre. Diastereomeric mixtures of hydroxyalkyl radical adducts are clearly resolved by ENDOR spectroscopy. Conformations of these radicals have been assigned based on the 1H and 13C hyperfine splittings (HFS's) and by differential optimum ENDOR temperatures. Definitive assignments of carbon-centered radical adducts of DMPO and PBN are shown to be feasible by monitoring the β-13C HFS's of the radical addend. Long-range γ-H HFS's from the added radical group can be observed when the deuterated spin trap PBN-d14 is used. The production of 13C labeled hydroxyalkyl adducts of nitrones (e.g., DMPO–13CH2OH, from the reaction of hydroxyl radicals with added 13CH3OH) is shown to be useful as an improved EPR spectroscopic method for the verification of the presence of hydroxyl radicals.

Spin-label studies of lipid-protein interactions with reconstituted band 3, the human erythrocyte chloride-bicarbonate exchanger

1998 ◽  
Vol 76 (5) ◽  
pp. 815-822 ◽  
Author(s):  
Andrew M Taylor ◽  
Anthony Watts
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Protein Interactions ◽  
Spin Label ◽  
Acyl Chain ◽  
Lateral Diffusion ◽  
Band 3 ◽  
Paramagnetic Resonance ◽  
A Value ◽  
Lipid Protein Interactions ◽  
Electron Paramagnetic

Lipid-protein interactions in reconstituted band 3 preparations were investigated by using spin-labeled lipids in conjunction with electron paramagnetic resonance (EPR) spectroscopy. Purified erythrocyte band 3 was reconstituted into egg phosphatidylcholine liposomes at high protein density with preservation predominantly of the dimeric state. Lipid-protein associations were revealed by the presence of a component in the EPR spectra that, when compared to spectra obtained from protein-free bilayers, indicated that lipid chain motions are restricted by interactions with the protein. From the fraction of the motionally restricted component obtained from the phosphatidylcholine spin-label, a value of 64 ± 14 annular lipids per band 3 dimer was obtained. This agrees with a value of 62 for the number of lipids that may be accommodated around the electron density map of a band 3 dimer. Selectivity of various spin-labeled lipids for the protein revealed that androstanol had a lower affinity for the band 3 interface, whereas a distinct preference was observed for the negatively charged lipids phosphatidylglycerol and stearic acid over phosphatidylcholine. This preference for negatively charged lipids could not be screened by 1-M salt, indicating that electrostatic lipid-protein interactions are not dominant. Estimates of annular lipid exchange rates from measured acyl chain segmental motions suggested that the rate of exchange between bilayer and boundary lipids was ~106 s-1, at least an order of magnitude slower than the rate of lipid lateral diffusion in protein-free bilayers.Key words: band 3, reconstitution, electron paramagnetic resonance, lipid-protein interactions.

scholarly journals Chimeric Lactase Capable of Spontaneous and Strong Immobilization on Cellulose and Development of a Continuous-Flow System for Lactose Hydrolysis at High Temperatures

2010 ◽  
Vol 76 (24) ◽  
pp. 8071-8075 ◽  
Author(s):  
G. A. Velikodvorskaya ◽  
T. V. Tikhonova ◽  
I. D. Gurvits ◽  
A. S. Karyagina ◽  
N. V. Lavrova ◽  
...  
Keyword(s):  
Continuous Flow ◽  
Fusion Proteins ◽  
Flow System ◽  
Thermophilic Bacterium ◽  
Hydrolysis Rate ◽  
Lactose Hydrolysis ◽  
Lactase Activity ◽  
Thermoanaerobacter Ethanolicus ◽  
A Value ◽  
Cellulose Binding

ABSTRACT Recombinant plasmids containing fusion proteins composed of two different modules were constructed and expressed in Escherichia coli. The modules encoded the lactase LacA (LacZ) from the thermophilic bacterium Thermoanaerobacter ethanolicus and the cellulase CelD, a cellulose-binding module (CBM) from Anaerocellum thermophilum. The CelD CBM provides a spontaneous and strong sorption of the fusion proteins onto a cellulose carrier. The enzymatic activities of both the free LacA protein and LacA-CelD CBM fusion proteins immobilized onto the cellulose carrier were assessed. The LacA activity of the fusion protein was dependent upon its position with respect to the CBM. The highest level of lactase activity and stability was observed when the lactase domain was localized at its N terminus. A continuous-flow column reactor of lactase immobilized on a cellulose carrier was constructed, and its activity was assessed. The lactose hydrolysis rate for a 150 mM (5%) solution at a flow rate of 1 reactor volume per min was 75%, which is a value optimal for further whey transformation into glucose/galactose syrup.

Electron Paramagnetic Resonance of Methyl Radicals on Porous Glass Surface

Science ◽  
1966 ◽  
Vol 154 (3747) ◽  
pp. 381-382 ◽  
Author(s):  
M. Fujimoto ◽  
H. D. Gesser ◽  
B. Garbutt ◽  
A. Cohen
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Porous Glass ◽  
Glass Surface ◽  
Methyl Radicals ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic
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