Time-Resolved ESR Studies on Photosensitized Reaction of Maleic Anhydride in Alcohols: CIDEP Memory Transfer in Spin-Adduct Formation

1992 ◽  
Vol 65 (6) ◽  
pp. 1672-1678 ◽  
Author(s):  
Keishi Ohara ◽  
Hisao Murai ◽  
Keiji Kuwata
Keyword(s):  
Maleic Anhydride ◽  
Adduct Formation ◽  
Spin Adduct ◽  
Memory Transfer ◽  
Time Resolved

Novel Phases in the V-P-O Catalytic System from Oxovanadium Hydrogenphosphate Precursors

1994 ◽  
Vol 346 ◽  
Author(s):  
P. Amoros ◽  
M. D. Marcos ◽  
J. Alamo ◽  
A. Beltran ◽  
P. Beltran
Keyword(s):  
Maleic Anhydride ◽  
High Temperatures ◽  
Catalytic System ◽  
Mild Oxidation ◽  
Time Resolved ◽  
X Ray ◽  
Redox Partners ◽  
Catalytic Cycles ◽  
Diffractometric Study ◽  
New Phase

ABSTRACTSeveral biphasic VOP04/(VO)2P2O7 redox partners seem to be active in the catalytic cycles involved in the mild oxidation of simple hydrocarbons to maleic anhydride. The present X-ray time resolved thermal-diffractometric study reveals the existence of a new anhydrous variety of the oxidized form, ω-VOPO4, which may appear as an intermediate in the formation of the well known β-VOPO4. This new phase only remains well crystallized at relatively high temperatures, and when it is allowed to cool down in wet air VOPO4·2H2O results. In turn, another well defined phase, VOPO4·1.58H2O, can be recognized in the course of the hydration process.

Spin adduct formation from lipophilic EMPO-derived spin traps with various oxygen- and carbon-centered radicals

2005 ◽  
Vol 69 (2) ◽  
pp. 297-305 ◽  
Author(s):  
Klaus Stolze ◽  
Natascha Udilova ◽  
Thomas Rosenau ◽  
Andreas Hofinger ◽  
Hans Nohl
Keyword(s):  
Adduct Formation ◽  
Spin Adduct ◽  
Spin Traps

Luminescent Terbium Complexes with Polymer Ligands

2004 ◽  
Vol 69 (2) ◽  
pp. 309-321 ◽  
Author(s):  
Drahomír Výprachtický ◽  
Věra Cimrová ◽  
Stanislav Kukla ◽  
Luďka Machová
Keyword(s):  
Energy Transfer ◽  
Maleic Anhydride ◽  
Diethyl Maleate ◽  
Time Resolved ◽  
Lanthanide Ion ◽  
Transfer Processes ◽  
Donor Acceptor ◽  
Complexing Properties ◽  
Terbium Complexes ◽  
Polymer Ligands

Alternating and statistical copolymers of 9-vinylcarbazole with diethyl fumarate (1), diethyl maleate (2), methacrylic acid (3), maleic anhydride (4), or maleic acid (5) were synthesized and characterized. These copolymers were tested as polymer ligands, that might be able to suppress the environmental vibronic quenching of a lanthanide ion and, simultaneously, to function as energy donors in the ligand-to-metal energy transfer processes. Time-resolved luminescence of a series of [Tb(III)-ligand] complexes in common and deuterated solvents revealed that the complexing properties of copolymers 3 or 5 are stronger than those of 1 or 2. Consequently, the strong binding affinity decreases the ligand-metal (donor-acceptor) distance and gives rise to an efficient ligand-to-metal energy transfer. Thus, the intensities of the long-lived emission (5D4→7F6, 5D4→7F5, 5D4→7F4, 5D4→7F3) of the [Tb(III)-3], [Tb(III)-5], and [Tb(III)-1] or [Tb(III)-2] complexes were found to be eight times, five times, and less than twice that of uncomplexed Tb3+, respectively.

Vascular NAD(P)H oxidase is distinct from the phagocytic enzyme and modulates vascular reactivity control

2001 ◽  
Vol 280 (2) ◽  
pp. H658-H667 ◽  
Author(s):  
Heraldo P. Souza ◽  
Francisco R. M. Laurindo ◽  
Roy C. Ziegelstein ◽  
Carlos O. Berlowitz ◽  
Jay L. Zweier
Keyword(s):  
Nadph Oxidase ◽  
Vascular Tone ◽  
Vascular Reactivity ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Adduct Formation ◽  
Spin Adduct ◽  
Ros Generation ◽  
Resonance Spectroscopy ◽  
Dependent Manner ◽  
Significant Difference

An NAD(P)H oxidase has been hypothesized to be the main source of reactive oxygen species (ROS) in vessels; however, questions remain about its function and similarity with the neutrophil oxidase. Therefore, vascular superoxide generation was measured by electron paramagnetic resonance spectroscopy using the spin-trap 5,5′-dimethly-pyrroline- N-oxide in aortas from wild-type (WT) and gp91phox-deficient mice (gp91phox−/−), which do not have a functioning neutrophil NADPH oxidase. There was no significant difference between radical adduct formation by WT or gp91phox−/− mouse aortas either at baseline or after stimulation with NADPH or NADH. Also, spin-adduct formation was identical in the 100,000- g pellets obtained from WT and gp91phox−/− mouse aortas. SOD mimetics and the flavoenzyme inhibitor diphenyleneiodonium blocked spin-adduct formation from both intact vessels and particulate fractions. Other pharmacological inhibitors of metabolic pathways involved in ROS generation had no effect on this phenomenon. To examine the role of this enzyme in vascular tone control, aortic rings were suspended in organ chambers and preconstricted with phenylephrine to reach half-maximal contraction. Exposure to NADPH elicited a 20% increase in vascular tone, which was decreased by SOD mimetics in a concentration-dependent manner, suggesting that superoxide was responsible for this phenomenon. NADH had no effect on vascular tone. Thus superoxide is generated in the vessel wall by an NAD(P)H-dependent oxidase, which modulates vascular contractile tone. This enzyme is structurally and genetically distinct from the neutrophil NADPH oxidase.

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