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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The photoinduced electron transfer at low temperatures in phospholipide membranes (liposomes) containing chlorophyll and 3 X 10-docsilpalmitate has been investigated. The reduction of 3 X 10-docsilpalmitate was estimated by ESR spectrometry. When diffusion movement of the molecules in membranes was blocked by low temperatures the photoinduced electron transfer has been found. The mechanism of these phenomena were analyzed on the base of donor-acceptor interaction through sigma bonds in hydrocarbon bridged donor-acceptor complexes. The separation of charges in these complexes is regarded as occurs by the migration of a hole along the hydrocarbon system. An approximate estimate of the charge mobility in the saturated hydrocarbon side chain of chlorophyll and activation energy of these movement was obtained.
Mol Biol (Mosk)
PMID:[Photoinduced electron transfer through the hydrocarbon zone of membranes at low temperatures]. 631 19

Rat thymocytes, spleen lymphocytes and isolated nuclei were incubated with fatty acids and then labelled with 5-doxylstearic acid and 12-doxylstearic acid. The ESR spectra only in the case of 5-doxylstearic acid showed changes which were demonstrable only under those conditions which resulted in cytolysis. Thymocytes in medium with 10% serum showed the effect at 10 microM, splenic lymphocytes at 100 microM. The effect was maximal at 2 min and was not enhanced by higher concentrations. The uptake of fatty acid by spleen cells required to cause this change was determined using 14C-oleic acid, to be 0.6 mumol/g tissue. This quantity is less than that required (label:lipid ratio less than 1:10) to produce major perturbations in membranes. Free fatty acids of C-8 to C-18 produced the effect, but not esters or amides. It was concluded that free fatty acids induce changes proximal to the polar region of membrane lipids which, if not progressive and essential to the ultimate process of lysis, are at least indicative of impending cell death at an early time.
Mol Cell Biochem 1983
PMID:Spin labelling studies of cytolysis induced by fatty acids. 668 30

The fluoride, chloride and bromide complexes of horseradish peroxidase were investigated by optical methods, NMR and ESR. The galide binding may be increased or reduced by means of enzyme-substrate complex formation of horseradish peroxidase with aromatic donors. Both sign and magnitude of the effect depends on galide ligand properties and structure of the donor's molecule. The maximum of the galide complex optical density removes redwise with the galide weight increasing. Cloride and bromide binding leads to the appreciable decrease of the high-spin portion in ferriheme spin equilibrium. The cloride complex of horseradish peroxidase demonstrates a low symmetry of the ligand field, in comparison of the fluoride complex.
Mol Biol (Mosk)
PMID:[Properties of the halide complexes of horseradish peroxidase in the presence of aromatic substrates]. 685 60

ESR spin trapping was utilized to study the singlet oxygen (1O2) generation in the reaction of superoxide (O2) with H2O2. The spin trap used was 2,2,6,6-tetramethyl-4-piperdone. Incubation of xanthine, xanthine oxidase and H2O2 generated 1O2 spin adduct signal. Omission of xanthine, xanthine oxidase or H2O2 caused a sharp decrease in 1O2 generation. 1O2 scavenger, sodium azide, inhibited 1O2 generation while .OH scavenger, ethanol, only slightly decreased the signal intensity. Potassium superoxide (KO2) decomposition generated 1O2. Catalase and sodium azide inhibited 1O2 generation and H2O2 enhanced it. The results demonstrate that O2 is capable of generating 1O2 upon reaction with H2O2.
Biochem Mol Biol Int 1995 May
PMID:Singlet oxygen generation in the superoxide reaction. 766 19

The generation of free radicals by Cr(IV) from lipid hydroperoxides was investigated by ESR spin trapping. The spin trap used was 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Reaction of Cr(VI) with ascorbate was used as a source of Cr(IV). Incubation of Cr(VI) with ascorbate generated Cr(IV) and Cr(V). Addition of cumene hydroperoxide generated DMPO/R adduct with an enhancement of Cr(V) signal. Addition of Mn(II), whose function is to remove Cr(IV), caused dose-dependent inhibition of DMPO/R formation. Similar results were obtained using t-butyl hydroperoxide. Metal ion chelators, deferoxamine, 1,10-phenanthroline and diethylenetriaminepentaacetic acid inhibited DMPO/R formation in the order of deferoxamine > 1,10-phenanthroline > diethylenetriaminepentaacetic acid. The results suggest the possible role of Cr(IV) and its mediated free radical generation from lipid hydroperoxides in the mechanism of Cr(VI) carcinogenesis.
Biochem Mol Biol Int 1995 Jun
PMID:Generation of free radicals by Cr(IV) from lipid hydroperoxides and its inhibition by chelators. 766 36

The interaction between ubiquinones and vitamin E was studied in the inner membranes of rat liver mitochondria, liposomes and human erythrocyte plasma membranes. Free radicals were produced by addition of exogenous oxidants, and their reaction with chromanols and ubiquinone was followed by ESR and HPLC. Membranes were made deficient in ubiquinone but sufficient in alpha-tocopherol and were reconstituted with added ubiquinone. With these membrane preparations it was shown that (i) in the inner mitochondrial membranes there is a requirements for ubiquinone in the enzymatic recycling of vitamin E; (ii) succinate-ubiquinone reductase incorporated in liposomes cannot protect vitamin E in the absence of ubiquinone and (iii) in human erythrocyte plasma membranes protection against the loss of vitamin E can be provided by NADH-cytochrome-b5-dependent enzymatic recycling. We conclude that ubiquinonols (ubisemiquinones) reduce vitamin E through electron transport.
Mol Aspects Med 1994
PMID:Interactions between ubiquinones and vitamins in membranes and cells. 775 45

2-Methyl-2-nitrosopropane (MNP) has long been known to undergo photochemical and thermal decomposition, generating di-tert-butyl nitroxide, in organic solvent. The present study was undertaken to demonstrate that MNP can be used as a caged-nitric oxide (NO), which can liberate NO upon illumination. Photolysis of MNP leads to the generation of tert-butyl radical and NO, as detected by spin-trapping/ESR spectroscopy and by oxyhemoglobin/visible spectroscopy, respectively. Using soluble guanylate cyclase in neuroblastoma N1E-115 cells as an NO target, we found that MNP in the presence of light caused a dose- and time-dependent increase in cGMP. Finally, illumination of a solution of MNP was also found to induce relaxation of preconstricted isolated rat pulmonary artery rings. These studies demonstrated that MNP can be useful biochemical research tool for delivering NO in a controlled manner, by using light.
Mol Pharmacol 1994 Oct
PMID:Biological studies of a nitroso compound that releases nitric oxide upon illumination. 796 50

The conversion of the closed circular double stranded supercoiled DNA (pBR322) to the nicked circular form and linear form was used to investigate DNA nicking induced by the reactions of Cu(II) complexes with hydrogen peroxide (H2O2). As a result, the dose-response curve for the CuII(en) (en:ethylenediamine) mediated H2O2 dependent DNA nicking was observed. For a fixed concentration of CuII(en)2 (1 mM), the concentration of H2O2 producing a maximum extent of DNA nicking was 100 mM. On the other hand, for a fixed concentration of H2O2 (100 mM), the concentration of CuII(en)2 was 1 mM. That is, when the concentration ratio of H2O2 to CuII(en)2 was 100, a maximum extent of DNA nicking was observed. This result is a good accordance with that observed by thiobarbituric acid (TBA) and ESR-spin trapping methods. This result gives first experimental evidence that Cu(II) complex did cause the DNA damage in the presence of H2O2. On the other hand, CuII(edta) (edta: ethylenediaminetetraacetic acid) did not cause the DNA strand breaks with the reaction of H2O2, but it was activated by addition of the biological reductant such as ascorbic acid in the presence of H2O2 to cause the DNA strand breaks.
Biochem Mol Biol Int 1993 Nov
PMID:DNA single strand breakage by copper(II) complexes and hydrogen peroxide at physiological conditions. 811 20

The fluidity of isolated chicken ventricular plasma membranes was investigated by ESR spectroscopy, using three doxylstearic spin labels (5-SASL, 10-SASL and 16-SASL), and by fluorescence anisotropy measurements, using DPH probe. The analysis of 2T1 splitting constant and rotational correlation frequency have shown differences, during in-ovo development, characterized by a rigidification phase with a maximum at 19 days of development, just before hatching, followed by a fluidification phase after birth. These phenomena were also improved by DPH fluorescence and dynamical analysis of the hydrophobic 16-SASL probe.
J Mol Cell Cardiol 1993 Dec
PMID:Fluidity of chicken ventricular plasma membranes during development in-ovo and after birth: spin labelling and fluorescence studies. 815 63

Oxidation of vanadyl sulfate by H2O2 involves multiple reactions at neutral pH conditions. The primary reaction was found to be oxidation of V(IV) to V(V) using 0.5 equivalent of H2O2, based on the loss of blue color and the visible spectrum. The loss of V(IV) and formation V(V) compounds were confirmed by ESR and 51V-NMR spectra, respectively. In the presence of excess H2O2 (more than two equivalents), the V(V) was converted into diperoxovanadate, the major end-product of these reactions, identified by changes in absorbance in ultraviolet region and by the specific chemical shift in NMR spectrum. The stoichiometric studies on the H2O2 consumed in this reaction support the occurrence of reactions of two-electron oxidation followed by complexing two molecules of H2O2. Addition of a variety of compounds--Tris, ethanol, mannitol, benzoate, formate (hydroxyl radical quenching), histidine, imidazole (singlet oxygen-consumption that also used V(IV) as the reducing source. This reaction requires concomitant oxidation of vanadyl by H2O2, favoured at low H2O2:V(IV) ratio. Another secondary reaction of oxygen release was found to occur during vanadyl oxidation by H2O2 in acidic medium in which the end-product was not diperoxovanadate but appears to be a mixture of VO3+ (-546 ppm), VO3+ (-531 ppm) and VO2+ (-512 ppm), as shown by the 51V-NMR spectrum. This reaction also occurred in phosphate-buffered medium but only on second addition of vanadyl. The compounds that stimulated the oxygen-consumption reaction were found to inhibit the oxygen-release reaction. A combination of these reactions occur depending on the proportion of the reactants (vanadyl and H2O2), the pH of the medium and the presence of some compounds that affect the secondary reactions.
Mol Cell Biochem 1993 Dec 08
PMID:Multiple reactions in vanadyl-V(IV) oxidation by H2O2. 817 31


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