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At least 433 records · Page 24Linked to original sources
PubMed1998

The role of structural factors of anthraquinone compounds and their quinone-modified analogues in NADH dehydrogenase-catalysed oxygen radical formation.

Anthraquinone compounds belong to the most important class of clinical antitumour agents. However, their use is limited by their peroxidating activity, being the consequence of free radical formation initiated by three oxyreductases. This activity is considered to be the main cause of cardiotoxic effects. The affinity of anthraquinone compounds to these enzymes is an essential factor governing the rate of one-electron transfer and the generation of oxygen radicals. A series of novel derivatives and analogues of natural and synthetic anthraquinones has been examined with the aim of identifying the structural factors essential for the ability to stimulate oxygen radical formation catalysed by NADH dehydrogenase. Functional groups and moieties favouring or disfavouring the interaction of the compounds with the enzyme have been determined. The quinonoid moiety as well as at least two phenolic groups in peri positions favoured the affinity of these compounds for NADH dehydrogenase. The modification of the quinonoid structure to iminoquinonoid or carboquinonoid forms dramatically decreased interaction with the enzyme. The O'-substitution by a bulky group in the sugar moiety of daunorubicin decreased the ability of the derivatives to stimulate oxygen radical formation. It has also been shown that the presence of an ionizable amino group on the sugar moiety of daunorubicin favours interaction with the NADH dehydrogenase. However, its location is not essential for this effect.

Anthraquinones↗
PubMedDate not supplied

Biotransformations and plasma-level curves of chiral 1,4-benzodiazepine-2-ones.

Biotransformations of chiral 1,4-benzodiazepine-2-ones, (S)- and (R)-1 (7-chloro-1,3-dihydro-3 (S and R)-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one) in untreated and phenobarbital-pretreated rats were investigated. In urine, a 4'-oxygenated metabolite (compound 2) was identified as the biotransformation product from both enantiomers, (S)-2 being present in much higher amounts than (R)-2. Unchanged parent compounds were not found in urine. In plasma, 3'- and 4'-oxygenated metabolites were identified after administration of (S)-1 and (R)-1, respectively. The metabolite possessing an R-configuration was present in much lower amounts. The maximum concentrations of (R)-1 in plasma, following a single dose, was about 6 time as high as the maximum plasma concentration of (S)-1. Faster biotransformation and elimination of (S)-1 is assumed to be the explanation of these findings.

Animals↗
PubMed2003

Process monitoring of anaerobic azo dye degradation by high-performance liquid chromatography-diode array detection continuously coupled to membrane filtration sampling modules.

Process integrated microfiltration and ultrafiltration based membrane sampling modules were compared by means of HPLC with diode array detection based monitoring of an anaerobic azodye biodegradation process. The sampling matrix consisted of anaerobic sludge from a municipal wastewater treatment plant. The hydrolysed azo dye Reactive Black 5 (RB5-H) and three products (ionic and nonionic) released from reductive cleavage under anaerobic conditions were continuously monitored by simultaneously separation by ion-pair chromatography. Microfiltration membrane-based sampling showed no retention for any compound observed. Sampling by ultrafiltration significantly retained the observed ionic compounds between 58 and 83% whereas a nonionic compound was not retained. On-line monitoring of an oxygen-sensitive compound was possible whereas off-line detection failed. Robust long time monitoring could be performed for up to 1 week without cleaning the membrane.

Anaerobiosis↗
PubMed2006

Kinetics of nitrogen removal from sanitary landfill leachate.

Leachates from municipal landfill 'Lublinek' in Lodz city (Poland) were treated in two-sludge sequence batch reactor systems (type ND). The external carbon source--sodium acetate was used in denitrification. Two versions were tested--with and without supernatant recirculation from D-SBR to N-SBR. The 99% removal of inorganic nitrogen compounds was achieved in both versions. Due to recirculation, the buffering (by means of sodium bicarbonate) was not necessary. Kinetic models for nitrification and denitrification processes were proposed. Kinetic parameters of the models were estimated by the optimization method. The experimental results of both nitrification steps (oxidation of ammonia to nitrites and nitrites to nitrates) were best fitted with the interactive limitation model of nitrogen compounds and oxygen. The denitrification process was limited only by the concentration of nitrogen compounds.

Bioreactors↗
PubMed1991

The antioxidant properties of a novel zinc-carnosine chelate compound, N-(3-aminopropionyl)-L-histidinato zinc.

A zinc-carnosine chelate compound, Z-103, attenuates gastric mucosal injuries and inhibits the increase of lipid peroxide in the gastric mucosa induced by burn shock or ischemia-reperfusion. However, the exact mechanism of the antioxidative effect of Z-103 is not clear. The antioxidant properties of a novel anti-peptic ulcer agent Z-103 in vitro were compared with those of zinc ion and L-carnosine. Z-103 scavenged superoxide anion radicals. Z-103 and ZnSO4, but not L-carnosine, inhibited the superoxide generation from polymorphonuclear leukocytes stimulated by opsonized zymosan, and also inhibited the generation of hydroxyl radicals by the Fenton reaction. The increase of lipid peroxides produced by rat brain homogenates and liver microsomes was also inhibited by Z-103 and ZnSO4. These findings indicate that the strong anti-ulcer and antioxidative actions of Z-103 in vivo are due to a combination of these antioxidant actions in vitro.

Anti-Ulcer Agents↗
PubMed1974

Inhibition and uncoupling of photophosphorylation in isolated chloroplasts by organotin, organomercury and diphenyleneiodonium compounds.

1. Trialkyltin, triphenyltin and diphenyleneiodonium compounds inhibited ADP-stimulated O(2) evolution by isolated pea chloroplasts in the presence of phosphate or arsenate. Tributyltin and triphenyltin were the most effective inhibitors, which suggests a highly hydrophobic site of action. Phenylmercuric acetate was a poor inhibitor of photophosphorylation, which suggests that thiol groups are not involved. 2. Triethyltin was a potent uncoupler of photophosphorylation by isolated chloroplasts in media containing Cl(-), but had little uncoupling activity when Cl(-) was replaced by NO(3) (-) or SO(4) (2-), which are inactive in the anion-hydroxide exchange. It is suggested that uncoupling by triethyltin is a result of the Cl(-)-OH(-) exchange together with a natural uniport of Cl(-). Tributyltin, triphenyltin and phenylmercuric acetate had low uncoupling activity, probably because in these compounds the uncoupling activity is partially masked by inhibitory effects. 3. At high concentrations the organotin compounds caused inhibition of electron transport uncoupled by carbonyl cyanide m-chlorophenylhydrazone or NH(4)Cl. At these high concentrations the organotin compounds may be producing a detergent-like disorganization of the membrane structure. In contrast, diphenyleneiodonium sulphate inhibited uncoupled electron transport at low concentrations; however, this inhibition is less than the inhibition of photophosphorylation, which suggests that the compound also inhibits the phosphorylation reactions as well as electron transport. 4. The effects of these compounds on basal electron transport were complex and depended on the pH of the reaction media. However, they can be explained on the basis of three actions: inhibition of the phosphorylation reactions, uncoupling and direct inhibition of electron transport. 5. The inhibition of cyclic photophosphorylation in the presence of phenazine methosulphate by diphenyleneiodonium sulphate shows that it inhibits in the region of photosystem 1.

Adenosine Diphosphate↗
PubMed1994

Degradation of morpholine by Mycobacterium aurum MO1.

When Mycobacterium aurum MO1 was grown with morpholine, the release of ammonia into the supernatant was proportional to the disappearance of morpholine, showing that this compound was mineralized. MO1 was able to grow in high concentrations of morpholine but accumulation of ammonia inhibited growth and degradation of morpholine. Immobilization of bacterial cells in carrageenan gel beads showed that morpholine degradation in these conditions began earlier and was faster than in free culture. One of the two branches of the lower pathway of morpholine biodegradation was induced while the other branch was inhibited in the presence of morpholine. Strain MO1 grew on heterocyclic compounds similar to morpholine, demonstrating that MO1 is able to degrade heterocyclic compounds containing nitrogen atoms (piperidine and pyrrolidine). Compounds containing sulphur or oxygen atoms or compounds with double bonds were not degraded.

Ammonia↗
PubMed2001

[IR characteristics of oxide].

In this paper the chief IR characteristics of oxide was summarized. The relationship between the IR characteristics of oxide and the structures of oxide was discussed. The results show that the organic compound and inorganic compound have great infrared activity, and have intense and wide absorption peaks. This provides the strong basis on which we can distinguish the oxide from the compound.

Inorganic Chemicals↗
PubMed1997

Binding of nitric oxide to thiols and hemes in hemoglobin H: implications for alpha-thalassemia and hypertension.

Our earlier studies suggested an association between alpha-thalassemia and hypertension. We postulated that this association might involve trapping of the vasodilator nitric oxide (NO) by hemoglobin (Hb). Hb A has recently been shown to carry NO on its sulfhydryl groups in addition to its hemes. In this report we studied the interaction of purified Hb H as well as Hb A with NO. The number of reactive sulfhydryls were determined spectrophotometrically with bis-dithionitrobenzoate. Spectral studies and nitrosothiol measurements after treatment with NO or nitrosothiols indicated that all eight reactive sulfhydryls of Hb H were capable of binding NO. Hb A, however, was only able to bind and transfer two molecules of NO per tetramer. These findings support the biochemical basis for the association between alpha-thalassemia and hypertension.

Dithionitrobenzoic Acid↗