SEARCH · PubMed Health

Results for “Murexide”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1975

Murexide for determination of free and protein-bound calcium in model systems.

The determination with murexide of free and protein-bound calcium in model systems of known composition, ionic strength, and pH was investigated. The spectra of calcium murexide in the presence of varying amounts of calcium ions indicated that the absorption maximum fo calcium murexide complex occurs at 480 nm while that of murexide ion is at 520 nm. The absorbance at 509 nm is independent of calcium ion concentration and, therefore, could be used to measure the total dye. The spectra are pH dependent but constant in the range 6.5 to 7.0. The apparent dissociation constant of calcium murexide is dependent upon ionic environment, ionic strength, and free calcium ion concentration. The relationship between the apparent dissociation constant and free calcium concentration was established. Whole casein had no effect on the absorption spectra of calcium murexide and no affinity for calcium murexide complex or murexide ion. Beta-casein, at the concentrations employed, did not influence the dissociation fo calcium murexide. At pH 7.0, ionic strength .1, and 2 C, Beta-casein bound calcium as if there were 8.65 binding sites per molecule, each of pK 2.23, corresponding to an intrinsic association constant of 168.9 liters per mole.

Barbiturates↗

PubMed1986

Reduction of the metallochromic indicators murexide and tetramethylmurexide to their free radical metabolites by cytoplasmic enzymes and reducing agents.

Murexide underwent reduction by rat liver cytosolic fraction or a hypoxanthine-xanthine oxidase system to produce a free radical metabolite. Reduction of murexide by the freshly prepared cytosolic fraction depended upon the presence of ascorbic acid. N1-Methylnicotinamide, xanthine or hypoxanthine, in that order, could also serve as a source of reducing equivalents for the production of that free radical by the cytosolic fraction. Several thiol compounds (GSH, cysteine, and cysteamine), pyridine nucleotides (NADH, NADPH) and ascorbic acid were also effective in generating the murexide-derived free radical. Tetramethyl murexide was also reduced to its free radical derivative by a hypoxanthine-xanthine oxidase system.

Animals↗

PubMedDate not supplied

Murexide bleaching: a new direct assay method for characterizing reactive oxygen species.

The murexide (5,5'-nitrilodibarbituric acid, monoammonium salt) is an efficient scavenger for superoxide and hydroxyl radicals. When exposed to oxygen radicals, murexide is converted to a colorless alloxan derivative and its absorbance at 520 nm decreases in proportion to the radicals produced. It is used to detect these reactive oxygen species in biochemical systems such as acetaldehyde oxidation by xanthine oxidase and the respiratory burst of polymorphonuclear leukocytes induced by phorbol 12-myristate, 13-acetate. The method was sensitive enough to allow direct monitoring of the production of superoxides from 10(6) phorbol 12-myristate, 13-acetate polymorphonuclear leukocyte-stimulated cells. Moreover, murexide bleaching is inhibited in the presence of radical scavengers, allowing a comparison of their scavenging activities.

Barbiturates↗

PubMed1983

Generation of free radical metabolites and superoxide anion by the calcium indicators arsenazo III, antipyrylazo III, and murexide in rat liver microsomes.

At the concentrations usually employed as a Ca2+ indicator, arsenazo III undergoes a one-electron reduction by rat liver microsomes to produce an azo anion radical as demonstrated by electron spin resonance spectroscopy. Either NADH or NADPH can serve as a source of reducing equivalents for the production of this free radical by rat liver microsomes. The steady state concentration of the azo anion radical is proportional to the square root of the protein concentration, suggesting that the radical decays through a nonenzymatic second order process. The steady state concentration of the azo anion radical is not altered in the presence of metyrapone or CO, and is decreased in the presence of NADP+ or p-hydroxymercuribenzoate. These observations suggest that the formation of arsenazo III anion radical is mediated through NADPH-cytochrome P-450 reductase and not by cytochrome P-450. Under aerobic conditions, addition of arsenazo III to rat liver microsomes produces an increase in electron flow from NAD(P)H to molecular oxygen, generating both superoxide anion and hydrogen peroxide. The steady state concentration of the azo anion radical, but neither oxygen consumption nor superoxide anion formation, is enhanced by calcium and magnesium, suggesting an enhanced azo anion radical-stabilization by complexation with the metal ions. Accordingly, the arsenazo III anion radical signal is abolished in the presence of paramagnetic metal ions (Fe3+, Gd3+, and Ni2+) and enhanced in the presence of other diamagnetic metal ions (La3+). Antipyrylazo III is less effective than arsenazo III in increasing superoxide anion formation by rat liver microsomes, and gives a much weaker ESR spectrum of an azo anion radical. Murexide is reduced to the monodehydro-5,5'-iminobarbituric acid radical by rat liver microsomes, and its efficiency as a superoxide anion generator is intermediate between arsenazo III and antipyrylazo III.

Arsenazo III↗

PubMed1963