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PubMed1981

Reflectance spectrophotometric monitoring of the isolated perfused heart as a method of measuring the oxidation-reduction state of cytochromes and oxygenation of myoglobin.

Reflectance spectrophotometry was assessed as a means of detecting metabolic oxidation-reduction changes in cytochromes and the oxygenation level of myoglobin in isolated perfused rat hearts. The movement artefact due to the heartbeat was largely eliminated by appropriate design of the optical geometry. A considerable myocardial oxygen gradient was detected using myoglobin deoxygenation as an indicator. The oxygenation level of myoglobin oscillated in pace with the contraction/relaxation cycle of the heart, deoxygenation occurring during the systole. The inconsistency in the previous reports on the myoglobin oxygenation and the problems of spectrophotometry of the beating heart are discussed.

Animals↗
PubMed1986

[Oxidation-reduction status of the culture medium during the biosynthesis of amphotericin B].

The possibility of potentiometric estimation of the oxidation-reduction state of the fermentation broth during production of amphotericin B was studied. It was shown that the reduction capacity of the fermentation broth was high and did not change significantly during the antibiotic biosynthesis. It contained electrochemically active compounds in amounts providing stable potentials on the indicator electrodes. Both the platinum and the glass redoxmetric electrodes not sensitive to changes in the level of oxygen dissolved in the fermentation broth might be used for measuring the oxidation potential of the fermentation broth. Investigation of the dynamics of the oxidation potential changing revealed that during the process of amphotericin B biosynthesis the potential changed within wide ranges and every stage of the culture development was characterized by particular direction of the potential changing. This allowed, in combination with other parameters of the process, estimation of physiological activity of the culture at any moment of its growth.

Amphotericin B↗
PubMed1959

Drug resistance in trypanosomes: effects of metabolic inhibitiors, pH and oxidation-reduction potential on normal and resistant Trypanosoma rhodesiense.

A wide variety of metabolic inhibitors tested in vitro for trypanocidal activity on normal and drug-resistant strains of Trypanosoma rhodesiense showed no relation between acquired drug resistance and changes in specific enzymatic function. Oxidation-reduction potential is an important factor in trypanocidal action but is not obviously related to the development of resistance. The dependence on pH of the trypanocidal action of ionizing drugs against both normal and resistant trypanosomes supports the postulate that the development of resistance involves physical changes in cell structures associated with the uptake of drug.

Antimetabolites↗
PubMed2001

Effects of amitriptyline on diurnal variations of oxidation-reduction enzyme activities in rat lymphocytes during experimental desynchronosis.

We studied the effects of amitriptyline on diurnal variations of oxidative-reduction enzyme activities (succinate dehydrogenase, lactate dehydrogenase, and NADPH diaphorase) in rat peripheral blood lymphocytes during experimental desynchronosis. Desynchronosis was induced by constant light exposure for 14 days and manifested in a morning shift of maximum lactate dehydrogenase activity and elevated morning NADPH diaphorase activity. Amitriptyline normalized morning lactate dehydrogenase activity and diurnal variations in NADPH diaphorase activity.

Amitriptyline↗
PubMed1989

Oxidation--reduction midpoint potentials of the flavin, haem and Mo-pterin centres in spinach (Spinacia oleracea L.) nitrate reductase.

Oxidation-reduction midpoint potentials have been determined for the flavin, cytochrome b557 and Mo-pterin prosthetic groups of spinach (Spinacia oleracea L.) assimilatory nitrate reductase using visible, c.d. and room-temperature e.p.r. potentiometric titrations. At pH 7 and 25 degrees C, the midpoint potential for the FAD/FADH2 couple was determined by c.d. potentiometry to be -280 +/- 10 mV (n = 2). The redox potential for reduction of the haem was determined by visible potentiometry to be -123 +/- 10 mV (n = 1), significantly lower than the previously published value of -60 mV [Fido, Hewitt, Notton, Jones & Nasrulhaq-Boyce (1979) FEBS Lett. 99, 180-182]. Potentials for the Mo(VI)/Mo(V) and Mo(V)/Mo(IV) redox couples, determined by room-temperature e.p.r. potentiometry, were found to be +2 +/- 20 and -6 +/- 20 mV respectively. These values are very similar to the values previously determined for the FAD, haem and Mo-pterin centres in assimilatory nitrate reductase isolated from the unicellular green alga Chlorella vulgaris and indicate a close thermodynamic similarity between the two enzymes.

Bacterial Proteins↗
PubMed1982

Dielectric constant dependence of biological oxidation-reduction. 1. A model of polarity-dependent ferrocytochrome c oxidation.

A theoretical model for the effect of the dielectric constant (c) of the solvent medium on ferrocytochrome c oxidation by ferricyanide is developed to account for the observed variations of the rate constant (k) of reactions in aqueous binary mixtures with alcohols (less than 5-10 mol% ethanol and propranolol). A correlation between k and c is found if ln k is expressed as a function of the Kirkwood parameter (c-1)(2c+1). The results of calculations indicate that the use of the 'overall dipole moment' of cytochrome c in oxidoreduction studies is likely to be unreliable. Instead, the decrease in k in alcohol/water mixtures is best explained--in conformity with Onsager's theory of the reaction field--by a polarity effect on the dipole moment of the cytochrome c heme upon diffusion of the polar solvent molecules into the low dielectric constant heme crevice.

Alcohols↗
PubMed1985

Nitrous oxide reduction by members of the family Rhodospirillaceae and the nitrous oxide reductase of Rhodopseudomonas capsulata.

After growth in the absence of nitrogenous oxides under anaerobic phototrophic conditions, several strains of Rhodopseudomonas capsulata were shown to possess a nitrous oxide reductase activity. The enzyme responsible for this activity had a periplasmic location and resembled a nitrous oxide reductase purified from Pseudomonas perfectomarinus. Electron flow to nitrous oxide reductase was coupled to generation of a membrane potential and inhibited by rotenone but not antimycin. It is suggested that electron flow to nitrous oxide reductase branches at the level of ubiquinone from the previously characterized electron transfer components of R. capsulata. This pathway of electron transport could include cytochrome c', a component hitherto without a recognized function. R. capsulata grew under dark anaerobic conditions in the presence of malate as carbon source and nitrous oxide as electron acceptor. This confirms that nitrous oxide respiration is linked to ATP synthesis. Phototrophically and anaerobically grown cultures of nondenitrifying strains of Rhodopseudomonas sphaeroides, Rhodopseudomonas palustris, and Rhodospirillum rubrum also possessed nitrous oxide reductase activity.

Acetylene↗
PubMed2004

Oxidation-reduction potential regulates RpoS levels in Salmonella Typhimurium.

AIMS: The aim of this work was to investigate the connection between oxidation-reduction (redox) potential and stationary phase induction of RpoS in Salmonella Typhimurium. METHODS AND RESULTS: A lux-based reporter was used to evaluate RpoS activity in S. Typhimurium pure cultures. During growth of S. Typhimurium, a drop in the redox potential of the growth medium occurred at the same time as RpoS induction and entry into stationary phase. An artificially induced decrease in redox potential earlier during growth reduced the time to RpoS induction and Salmonella entered the stationary phase prematurely. In contrast, under high redox conditions, Salmonella grew unaffected and entered the stationary growth phase as normal, although RpoS induction did not occur. As a consequence, stationary phase cells grown in the high redox environment were significantly more heat sensitive (P < 0.05) than those grown under normal conditions. CONCLUSIONS: This work suggests that redox potential can regulate RpoS levels in S. Typhimurium and can thus, control the expression of genes responsible for thermal resistance. SIGNIFICANCE AND IMPACT OF THE STUDY: The ability to manipulate RpoS induction and control stationary phase gene expression can have important implications in food safety. Early RpoS induction under low redox potential conditions can lead to enhanced resistance in low cell concentrations to inimical processes such as heat stress. Inhibition of RpoS induction would abolish stationary phase protective properties making cells more sensitive to common food control measures.

Bacterial Proteins↗
PubMed2004

Synthesis of imidazolo analogues of the oxidation-reduction cofactor pyrroloquinoline quinone (PQQ).

Parallel syntheses of 2-hydro-, 2-methyl-, and 2-methoxycarbonylimidazo-7,9-dimethoxycarbonyl analogues of the oxidation-reduction cofactor pyrroloquinoline quinone [4,5-dihydro-4,5-dioxo-1H-pyrrolo[2,3-f]quinoline-2,7,9-tricarboxylic acid] have been developed. The properties of the imidazolo analogues in relation to the corresponding pyrrole analogues will be important in assessing the origins of catalysis and biological activity in the cofactor, which has recently been shown to be a vitamin.

Catalysis↗
PubMed1986

Determination of sialic acid residues in transferrin by oxidative-reductive immunoassay.

A method is described for the determination of sialic acid residues in glycoproteins displaying microheterogeneity in the sugar residue. The new method is based on combining an oxidative-reductive step with binding of the glycoprotein to an immunoadsorbent. After a mild oxidation with sodium metaperiodate the sugar is reduced with labeled sodiumborotritide. The chemical modification of the sugar residues does not seem to impair the binding of glycoprotein to the immunoadsorbent. The procedure, which has been elaborated for human transferrin, can be carried out in the presence of other substances in body fluids.

Antigen-Antibody Complex↗
PubMed1997

[Activity of oxidation-reduction enzymes in endotheliocytes of the intestinal hemomicrocirculatory bed under normal conditions and in portal hypertension].

An original quantitative examination of oxidation-reduction enzymes activity in endotheliocytes of hemomicroclrculatory vessels of jejunum and rectum submucosal base in normal state and in portal hypertension was performed by the authors. Comparative analysis of the activity of the enzymes studied revealed different metabolic processes intensity in these organs, dependent on current hemodynamic conditions. Cytochemical changes in hemomicrocirculatory bed are consistent with structural reorganizations that arise in the wall of vessels studied, consist of several phases and may be used as an assessment criterion for defining the portal hypertension stage.

Animals↗
PubMed1990

Oxidation-reduction potentials of cytochromes in Ascaris muscle mitochondria: high-redox-potential cytochrome b558 in complex II (succinate-ubiquinone reductase).

Oxidation-reduction midpoint potentials (Ems) were determined at pH 7.0 for cytochromes in the anaerobic respiratory chain of Ascaris mitochondria by redox titration techniques. Cytochrome b558, which is associated with complex II that functions as fumarate reductase in the terminal step of the respiratory chain, was shown to have an Em of -34 mV in the isolated complex II and -54 mV in mitochondria. These values are much higher than the value of Ascaris cytochrome b558. In contrast, Ems of cytochromes C + C1 and cytochrome b559.5 were determined in situ to be 235 mV and 78 mV, respectively, which are comparable to those of their mammalian counterparts.

Animals↗
PubMed1989

Role of arginine-38 in regulation of the cytochrome c oxidation-reduction equilibrium.

Arg-38 is an internal residue of mitochondrial cytochrome c that is close to heme propionate-7. Previous work comparing the behavior of cytochromes c from several species [Moore, G. R., Harris, D. E., Leitch, F. A., & Pettigrew, G. W. (1984) Biochim. Biophys. Acta 764, 331-342] has suggested that Arg-38 lowers the pKa of this propionate group and thereby accounts for the relative pH independence of the cytochrome c reduction potential from pH 5 to pH 8. The influence of Arg-38 on the oxidation-reduction equilibrium of yeast iso-1-cytochrome c has now been investigated by electrochemical, NMR, and theoretical analysis of six specifically mutated forms of this protein in which Arg has been replaced by Lys, His, Gln, Asn, Leu, or Ala. As the electron-withdrawing character of the residue at position 38 decreases, the reduction potential of the protein also decreases, with the largest decrease (ca. 50 mV) observed for the Ala variant. However, the variation in the reduction potentials of the mutants as a function of pH was similar to that observed for the wild-type protein. The effects of some of these mutations on the pKa values of His-33 and His-39 have been determined by NMR spectroscopy and found to be minimal. Calculations of the electrostatic free energy for the Leu-38 variant predict a decrease in the reduction potential of this mutant that is remarkably close to that observed experimentally. This work establishes that while Arg-38 contributes to the relatively high reduction potential of cytochrome c, this residue does not appear to be the sole functionality responsible for lowering the heme propionate-7 pKa.

Amino Acids↗
PubMed1986

Thermodynamic properties of oxidation-reduction reactions of bacterial, microsomal, and mitochondrial cytochromes P-450: an entropy-enthalpy compensation effect.

An optically transparent thin-layer electrode cell with a very small volume was used for determination of the formal reduction potentials of bacterial, microsomal, and mitochondrial cytochromes P-450. At an extrapolated zero concentration of dye, the bacterial cytochrome from Pseudomonas putida catalyzing the hydroxylation of camphor and the adrenal mitochondrial cytochrome catalyzing the cholesterol side-chain cleavage reaction had formal reduction potentials of -168 and -285 mV (pH 7.5 and 25 degrees C), respectively. The oxidation-reduction potentials for the rabbit liver microsomal cytochrome P-450 induced by 3-methylcholanthrene and the mitochondrial cytochrome for steroid 11 beta-hydroxylation were found as -360 and -286 mV, respectively. Potential measurements at different temperatures allowed documentation of the standard thermodynamic parameters for cytochrome P-450 reduction for the first time. All cytochromes tested were found to have a relatively large negative entropy change upon reduction. The extent of these changes is comparable to that observed for the ferric-ferrous couple of cytochrome c. An entropy-enthalpy compensation effect was observed among the four cytochromes P-450 examined although the correlation is weaker than that observed with cytochrome c isolated from various sources.

Adrenal Cortex↗
PubMed1982

Intracellular oxidation-reduction state measured in situ by a multichannel fiber-optic surface fluorometer.

The principles of the measurement in vivo of the oxidation-reduction state of intramitochrondrial pyridine nucleotides were used in establishing a multichannel fluorometer-reflectometer. This approach made possible the study of changes of mitochrondrial redox states in four different organs (brain, liver, kidney, and testis) of the same animal, as well as the monitoring of four different cortical areas of the same brain hemisphere. In the measurement of reduced nicotinamide adenine dinucleotide fluorescence, oximetric and movement artifacts are negligible, but blood volume changes and tissue absorption properties are a source of error. The corrected fluorescence is obtained by subtracting the reflectance from the fluorescence signed in 1:1 ratio., During graded hypoxia, the corrected fluorescence showed a gradual increase and was maximal during anoxia in all four organs tested.

Animals↗
PubMed1981

Binding of protoporphyrin to melanin and oxidation-reduction properties of melanin-protoporphyrin complex.

The binding of protoporphyrin to melanin and the effect of the binding of protoporphyrin to melanin on the oxidation-reduction properties of melanin were studied. Various concentrations of protoporphyrin were incubated with melanin suspensions. The amounts of protoporphyrin remaining in the supernatant after sedimentation of the melanin were determined. The amount of bound protoporphyrin was determined by extraction with 3 M HCl. The results showed that when the initial concentration of protoporphyrin was varied, the amounts of protoporphyrin bound were in accordance with Langmuir's isotherm. From these results it was calculated that at infinite concentration of protoporphyrin 7.62 +/- 0.38 microgram protoporphyrin would be bound to 1 mg melanin. The activity to catalyze the coupled oxidation of NADH and reduction of ferricyanide was less in the case of the melanin-protoporphyrin complex than the free melanin. It is suggested that the binding of a naturally occurring photosensitizer such as protoporphyrin to melanin may have significant biological effects viz (i) photosensitivity due to protoporphyrin, (ii) the chemical reactivity of melanin in internal organs, and (iii) protective action of melanin in skin against ultraviolet radiation.

Ferricyanides↗
PubMed1995

Selective inhibition of the mitochondrial permeability transition pore at the oxidation-reduction sensitive dithiol by monobromobimane.

In this paper we introduce monobromobimane, a thiol reagent, as a selective blocker of the recently identified dithiol whose oxidation-reduction status modifies voltage sensing by the mitochondrial permeability transition pore, a cyclosporin A-sensitive channel. Monobromobimane does not inhibit the phosphate carrier, nor does it interfere with Ca2+ transport, energy coupling or ATP production and transport. We show that monobromobimane selectively prevents the shift in pore gating potential caused by some dithiol oxidants or crosslinkers but not by increasing [Ca2+], allowing a clear distinction of the pore agonists which act at this site.

Adenosine Triphosphate↗