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PubMed1990

Scavenging of singlet molecular oxygen by imidazole compounds: high and sustained activities of carboxy terminal histidine dipeptides and exceptional activity of imidazole-4-acetic acid.

Singlet molecular oxygen was generated by illumination of phenosafranin in phosphate buffer at pH 7.5. Relative efficiencies of various imidazole compounds to form endoperoxides were assayed by following at 25 degrees C the rate of light- and imidazole-dependent bleaching of N,N-dimethyl-4-nitrosoaniline. Of over 30 imidazole compounds tested, imidazole-4-acetic acid, a major catabolite of histamine in mammals, exhibited the highest activity. L-Carnosine (beta-alanyl-L-histidine), a natural dipeptide prevalent in striated muscle of mammals, possessed several properties important for a physiologically significant scavenger of singlet oxygen. On a molar basis, this readily water-soluble C-terminal histidine dipeptide reacted with singlet oxygen two- to four-fold faster than free L-histidine and approximately two-fold faster than the N-terminal L-histidine dipeptides tested. Furthermore scavenging ability of L-carnosine did not appreciably increase or decrease with time of reaction, in contrast to behaviors exhibited by a number of other imidazole compounds that included some other C-terminal L-histidine dipeptides. The fungal metabolite, ergothioneine, blocked singlet oxygen generation by illuminated phenosafranin.

Carnosine↗
PubMed1986

Carotenoid compound crocetin improves cerebral oxygenation in hemorrhaged rats.

The carotenoid compound crocetin has been shown to increase oxygen diffusivity in vitro. In the present study the effect of crocetin on tissue oxygenation was examined in the cerebral cortex of rats subjected to hemorrhage. Twelve male Sprague-Dawley rats were anesthetized with pentobarbital and ventilation was controlled (PaCO2 = 33 mm Hg). A craniotomy was performed and the animals were hemorrhaged (20% of estimated total blood volume). Six of 12 animals then received a bolus of crocetin (2 U in 0.1 ml saline); the remaining animals received saline (0.1 ml i.v.) only. Values for mean arterial pressure. PO2, PCO2, pH, and hematocrit did not differ in rats that received either saline or crocetin. Tissue oxygen tension (PtO2) was measured at approximately 170 locations in the parietal cerebral cortex of each rat by a platinum-oxygen microelectrode technique. Results were compared by PtO2 frequency histograms. Crocetin as compared with saline treatment resulted in a right shift of the PtO2 frequency distribution and a significant decrease in the frequency of occurrence of low PtO2 values. The average of individual median PtO2 values was significantly greater in crocetin-treated animals as compared with those receiving saline (7.6 +/- 1.7 vs. 3.2 +/- 1.2 mm Hg, respectively). The results suggest that the carotenoid compound crocetin improves tissue oxygenation in the cerebral cortex of hemorrhaged rats.

Animals↗
PubMed1978

Influence of oxygen tension, sulfhydryl compounds, and serum on the motility and virulence of Treponema pallidum (Nichols strain) in a cell-free system.

The motility and virulence of Treponema pallidum (Nichols strain) were monitored during incubation in a modified tissue culture medium to study the effects of oxygen tension and medium composition on survival of the organism. A basal medium of Eagle minimal essential medium with 50% fresh, heat-inactivated normal rabbit serum was used inasmuch as better survival occurred with 50% normal rabbit serum than with lower concentrations. Addition of 0.5 to 2.0 mM dithiothreitol or 2.0 mM dithioerythritol to the basal medium led to significantly longer retention of T. pallidum viability in the presence of 3% oxygen than under aerobic or anaerobic conditions. The results of this investigation lend support to the classification of T. pallidum as a microaerophilic organism and provide direction for the design of potentially successful culture systems, with or without tissue culture cells.

Blood↗
PubMed2003

4H-1,2-benzoxazines with electron-withdrawing substituents on the benzene ring: synthesis and application as potent intermediates for oxygen-functionalized aromatic compounds.

A new general method for synthesizing functionalized 4H-1,2-benzoxazine derivatives is described. Although 4H-1,2-benzoxazine is one of the fundamental structure of the oxazine group, no general synthetic method for the heterocycle has been established. We found that 3-methoxycarbonyl-4H-1,2-benzoxazine was obtained in good yield when methyl 2-nitro-3-phenylpropionate was treated with an excess amount of trifluoromethanesulfonic acid. This methodology was also applicable for the synthesis of 4H-1,2-benzoxazine rings functionalized with various electron-withdrawing substituents on the benzene ring. Furthermore, we also show that the resulting 4H-1,2-benzoxazines can be used as precursors of functionalized o-quinone methides and multisubstituted phenols. This type of heterocycle can be a potent intermediate to oxygen-fuctionalized aromatic compounds.

Journal Article↗
PubMed1992

Structural studies of oxygen-bridged iron compounds.

Compound (I): cis-dichloro[mu-[bis[mu-[[2,6-diacetylpyridine dioximato](2-)-O:O']]dihydroxodiphenyl-diborato](3-)]- mu- mithoxydiiron, [Fe2(C30H29B2N6-O6)Cl2(CH3O)], M(r) = 804.9, monoclinic, Cc, a = 21.228 (6), b = 8.020 (2), c = 20.865 (5) A, beta = 105.2 (1) degrees, V = 3428 (2) A3, Z = 4, Dx = 1.56 g cm-3, lambda(Mo K alpha) = 0.7107 A, mu = 10.6 cm-1, F(000) = 1648, T = 275 K, R = 0.055 for 3018 unique reflections. Compound (I) contains a pseudo-twofold axis relating the two pyridine dioxime groups bound to the Fe atoms. In addition, two O atoms from the phenylborate moieties bridge the iron atoms, as does a methoxide. The two Cl atoms are bound to the seven coordinate metals axial to the methoxide. Compound (II): cis-dichloro[mu-[bis[mu-[[2,6-diacetylpyridine dioximato](2-)-O:O']]dihydroxodiphenyldiborato](3-)]-mu- hydroxodiiron, [Fe2(C30H29B2N6-O6)Cl2(OH)].H2O.2C2H3N, M(r) = 891.0, monoclinic, P2(1)/n, a = 11.860 (2), b = 20.911 (5), c = 16.175 (3) A, beta = 92.88 (1) degrees, V = 4006 (3) A3, Z = 4, Dx = 1.48 g cm-3, lambda(Mo K alpha) = 0.7107 A, mu = 9.1 cm-1, F(000) = 1832, T = 275 K, R = 0.051 for 7034 unique reflections. Compound (II) contains a hydroxide group replacing the methoxide in compound (I). The crystals also contain two acetonitriles of solvation. The bond lengths in the complex and the hydrogen-bonding pattern in the crystals are consistent with one of the bridging borate O atoms being protonated.(ABSTRACT TRUNCATED AT 250 WORDS)

Bridged-Ring Compounds↗
PubMed1987

Energy barriers in binding of carbon monoxide and oxygen to heme model compounds.

Binding of carbon monoxide and oxygen to sterically protected heme model compounds (basket-handle porphyrins) was investigated in liquid toluene at temperatures from 180 to 300 K by laser flash photolysis. Only a single exponential rebinding process from the solvent could be seen in the time range of 20 nsec to milliseconds. The fraction of ligands that initially escaped into the solvent decreased when the temperature was lowered, and the Arrhenius plots for the rebinding rate coefficients were found to deviate significantly from linearity. These findings suggest that protected heme model compounds might react according to a double energy-barrier scheme. In contrast, the reaction of an unprotected porphyrin can be described by a single energy barrier.

Carbon Monoxide↗
PubMed1990

Quantitative structure-retention relationship studies of odor-active aliphatic compounds with oxygen-containing functional groups.

High-quality regression equations (R greater than 0.996) modeling the gas chromatographic retention indices of 115 odor-active compounds on stationary phases of different polarity are generated by using the ADAPT software system. Multiple linear regression techniques are used to describe the statistical relationship between the Kováts retention indices and structure-based molecular descriptors. These descriptors encode topological, geometrical, and electronic features of the molecules. The utility of several new descriptors encoding functions of partial atomic charge and solvent accessible surface area is demonstrated. Quantitative predictions of odor threshold values for a subset of these compounds containing the alcohol functional group are also calculated by using a similar methodology.

Hydrocarbons↗
PubMed2004

The direct amino acid-catalyzed asymmetric incorporation of molecular oxygen to organic compounds.

We have disclosed the direct catalytic incorporation of 1O2 to aldehydes. The unprecedented amino acid-catalyzed asymmetric alpha-oxidation of aldehydes with molecular oxygen or air proceeded with high chemoselectivity and was a direct entry for the synthesis of both enantiomers of terminal diols. The results demonstrated that simple amino acids accomplished catalytic asymmetric oxidations with molecular oxygen or air, which has previously been considered to be in the domain of enzymes and chiral transition-metal complexes. The efficiency of the catalytic process may warrant the existence of an ancient pathway for the synthesis of hydroxylated organic compounds.

Journal Article↗
PubMed2005

Simultaneous anaerobic-aerobic biodegradation of halogenated phenolic compound under oxygen-limited conditions.

The successful application of co-immobilized aerobic-anaerobic biomass under limited aeration in wastewater treatment systems would eliminate the problems associated with the intermediates mono-chlorophenol (MCP) and di-chlorophenol(DCP) accumulations. With low initial pentachlorophenol (PCP) concentration, all PCP could be completely removed under oxygen-limited strict anaerobic conditions, and the removal efficiencies with different initial headspace oxygen percentage (IHOP) were not obviously different from each other. While at high initial PCP concentration, under strictly anaerobic conditions PCP and their intermediates were clearly higher than that under other conditions, and produced obvious accumulation, the highest PCP reduction was achieved by the system receiving 30 IHOP, oxygen-limited system also exhibited lower residual TOC concentration and lower concentration of metabolic intermediates MCP and DCP. These results suggested that under strictly anaerobic condition the reductive dechlorination of low chlorinated compounds became rate limiting in the reductive dechlorination pathway, less chlorinated compounds be more amenable to aerobic degradation, and the aerobes of outer layers could function under limited oxygen. The co-immobilized aerobic-anaerobic biomass for methanogenesis under limited-aeration for chlorophenol degradation might be an attractive and efficient alternative for the sequential anaerobic/aerobic system to achieve mineralization of a broad range of recalcitrance highly chlorinated organics and low final TOC concentrations.

Anaerobiosis↗
PubMed1992

[Role of sulfhydryl compounds in the oxygen radical induced injury of isolated gastric mucosal cells].

Gastric mucosal cells were separated by pronase-EDTA method and cultured. The cellular injury was produced by oxygen radicals provided by xanthine oxidase(XO)-xanthine(X) system. When the cells were subjected to the action of XO-X system, the cellular viability was decreased and leakage of lactate dehydrogenase (LDH) from the cells was significantly increased. In addition, the cellular contents of nonprotein sulfhydryls (NPSH) and protein sulfhydryls (PSH) were decreased. When the intracellular sulfhydryl content was decreased by N-ethylmaleimide (NEM, a depletor of endogenous sulfhydryls), the cell mortality and LDH leakage were increased in a time-dependent and dose-dependent manner. If glutathione or cysteamine (compounds containing-SH) was administered into the media, the cellular injury induced by XO-X system was notably inhibited, also in a dose-dependent manner. The above results suggest that sulfhydryls may play an important role in the cell defending mechanism against injury of gastric mucosal cells by oxygen radicals.

Animals↗
PubMed1996

Reactions of Singlet Oxygen with Organometallic Compounds. 4. Photooxidation of Cationic Iridium(I) and Rhodium(I) Complexes with Weakly Bonded Ligands.

Cationic complexes of the type [M(CO)S(PPh(3))(2)](+) (M = Ir, Rh; S = CH(3)CN) react with singlet oxygen to form the corresponding peroxo complexes [M(CO)S(PPh(3))(2)(O(2))](+). The solvent molecule remains coordinated to the metal in the oxygen adducts. The novel cationic iridium-peroxo complex is stable at room temperature, while the rhodium-peroxo complex is only stable below 0 degrees C. Rate constants for physical and chemical interaction of the complexes with singlet oxygen are somewhat smaller than those for related neutral complexes. Upon addition of alkenes (tetramethylethylene or 1-octene) to the peroxo complexes, neither oxidation of the olefins nor substitution of the acetonitrile ligand was observed. 1-Octene was isomerized to give mostly 2- and 3-octene by the cationic rhodium(I) complex. A cationic iridium complex which already possesses a coordinated diene ligand ([Ir(COD)(PPh(3))(2)](+)) did not react with or quench singlet oxygen.

Journal Article↗
PubMed1999

The oxygenase component of the 2-aminobenzenesulfonate dioxygenase system from Alcaligenes sp. strain O-1.

Growth of Alcaligenes sp. strain O-1 with 2-aminobenzenesulfonate (ABS; orthanilate) as sole source of carbon and energy requires expression of the soluble, multicomponent 2-aminobenzenesulfonate 2,3-dioxygenase system (deaminating) (ABSDOS) which is plasmid-encoded. ABSDOS was separated by anion-exchange chromatography to yield a flavin-dependent reductase component and an iron-dependent oxygenase component. The oxygenase component was purified to about 98% homogeneity and an alpha2beta2 subunit structure was deduced from the molecular masses of 134,45 and 16 kDa for the native complex, and the alpha and beta subunits, respectively. Analysis of the amount of acid labile sulfur and total iron, and the UV spectrum of the purified oxygenase component indicated one [2Fe-2S] Rieske centre per alpha subunit. The inhibition of activity by the iron-specific chelator o-phenanthroline indicated the presence of an additional iron-binding site. Recovery of active protein required strictly anoxic conditions during all purification steps. The FAD-containing reductase could not be purified. ABSDOS oxygenated nine sulfonated compounds; no oxygen uptake was detected with carboxylated aromatic compounds or with aliphatic sulfonated compounds. Km values of 29, 18 and 108 microM and Vmax values of 140, 110 and 72 pkat for ABS, benzenesulfonate and 4-toluenesulfonate, respectively, were observed. The N-terminal amino acid sequences of the alpha- and beta-subunits of the oxygenase component allowed PCR primers to be deduced and the DNA sequence of the alpha-subunit was thereafter determined. Both redox centres were detected in the deduced amino acid sequence. Sequence data and biochemical properties of the enzyme system indicate a novel member of the class IB ring-hydroxylating dioxygenases.

Alcaligenes↗
PubMed1989

Role of lipid peroxidation and oxygen radicals in compound 48/80-induced gastric mucosal injury in rats.

Repeated administration of a small dose of compound 48/80 induced acute gastric mucosal injury in rats. Thiobarbituric acid (TBA) reactants in the gastric mucosa were significantly increased and serum alpha-tocopherol was significantly decreased after the treatment. The total area of gastric lesions and the increase in TBA reactants in the gastric mucosa were significantly reduced by pretreatment with superoxide dismutase (SOD) and/or catalase, allopurinol and anti-rat polymorphonuclear leukocytes (PMN) antibody. Lipid peroxidation and oxygen radicals derived from both the xanthine-xanthine oxidase system and PMN may be involved in the pathogenesis of compound 48/80-induced gastric mucosal injury.

Animals↗
PubMed1996

Guanidino compounds generate reactive oxygen species.

Methylguanidine, guanidinoacetic acid and guanidinosuccinic acid are endogenous substances in body tissues. Extremely high levels of these substances are known to be related to the pathogenesis of epilepsy and renal failure such as uremia. In this study it was demonstrated that methylguanidine, guanidinoacetic acid and guanidinosuccinic acid, and arginine generate hydroxyl radicals in aqueous solution. These findings suggest that a high level of guanidino compounds accumulating near or within cells such as neurons (in an epileptogenic focus) or nephrons (in uremic patients) may cause free radical damage leading to these clinical disorders. Arginine may have a similar role in the pathogenesis of hyperarginemia.

Electron Spin Resonance Spectroscopy↗
PubMed1992

Protection by beta-carotene and related compounds against oxygen-mediated cytotoxicity and genotoxicity: implications for carcinogenesis and anticarcinogenesis.

beta-Carotene protects against photooxidative dermatitis in porphyric humans and mice by quenching of photoactivated species. Other actions of beta-carotene in vivo are explained on the basis of its ability to scavenge free radicals in vitro. For example, in guinea pigs treated with CCl4, beta-carotene decreases pentane and ethane production. Epidemiological studies link low serum beta-carotene levels to elevated risk of lung and other cancers, and in intervention trials, beta-carotene diminishes preneoplastic lesions. However, the dose/response relationships are not well established, and antineoplastic mechanisms await clarification. Given a radical quenching mechanism, beta-carotene should block tumor promotion, but more typically the site of action is progression and an even later role in invasion has not been ruled out. Some antineoplastic actions of carotenoids (such as increased rejection of fibrosarcomas in mice) are attributed to immunoenhancement; others may reflect conversion to retinoids and subsequent gene regulation. Carotenoids other than beta-carotene may act at an earlier stage of carcinogenesis or be more effective as anticarcinogens at certain target sites. As scavengers of hydroxyl radicals, canthaxanthin and astaxanthin are more effective than beta-carotene. Canthaxanthin is sometimes more effective than beta-carotene in chemoprevention, but it is sometimes completely ineffective. Lycopene quenches singlet oxygen more than twice as effectively as beta-carotene. However, the antineoplastic actions of lycopene or astaxanthin remain untested. Explorations of the interactions of carotenoids with other nutrients are just beginning. Dietary fat increases absorption of carotene but decreases antineoplastic effectiveness. Research is hampered by technical problems, including the unavailability of rigorous controls, the instability of carotenoids, and the heterogeneous phase structure induced by hydrophobic compounds in aqueous media. Areas of current controversy and promising approaches for future research are identified.

Animals↗
PubMed1984

Epoxidation of olefins by cytochrome P-450 model compounds: mechanism of oxygen atom transfer.

The mechanism of the Mn(III) porphyrin-catalyzed epoxidation of olefins by lithium hypochlorite is examined. The active oxidant is thought to be a high-valent manganese-oxo complex. It is shown that a relatively stable intermediate is reversibly formed upon interaction of the olefin and the oxo complex. The decomposition of this intermediate to Mn(III) porphyrin and epoxide is the rate-determining step of the catalytic cycle. Some analogies to the biochemical epoxidation of olefins catalyzed by cytochrome P-450 are discussed.

Alkenes↗