Ubiquinol

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Bernard L. Trumpower - One of the best experts on this subject based on the ideXlab platform.

  • mutational analysis of cytochrome b at the Ubiquinol oxidation site of yeast complex iii
    Journal of Biological Chemistry, 2006
    Co-Authors: Tina Wenz, Bernard L. Trumpower, Raul Covian, Petra Hellwig, Fraser Macmillan, Brigitte Meunier, Carola Hunte
    Abstract:

    Abstract The cytochrome bc1 complex is a dimeric enzyme of the inner mitochondrial membrane that links electron transfer from Ubiquinol to cytochrome c by a protonmotive Q cycle mechanism in which Ubiquinol is oxidized at one center in the enzyme, referred to as center P, and ubiquinone is rereduced at a second center, referred to as center N. To better understand the mechanism of Ubiquinol oxidation, we have examined catalytic activities and pre-steady-state reduction kinetics of yeast cytochrome bc1 complexes with mutations in cytochrome b that we expected would affect oxidation of Ubiquinol. We mutated two residues thought to be involved in proton conduction linked to Ubiquinol oxidation, Tyr132 and Glu272, and two residues proposed to be involved in docking Ubiquinol into the center P pocket, Phe129 and Tyr279. Substitution of Phe129 by lysine or arginine yielded a respiration-deficient phenotype and lipid-dependent catalytic activity. Increased bypass reactions were detectable for both variants, with F129K showing the more severe effects. Substitution with lysine leads to a disturbed coordination of a b heme as deduced from changes in the midpoint potential and the EPR signature. Removal of the aromatic side chain in position Tyr279 lowers the catalytic activity accompanied by a low level of bypass reactions. Pre-steady-state kinetics of the enzymes modified at Glu272 and Tyr132 confirmed the importance of their functional groups for electron transfer. Altered center N kinetics and activation of Ubiquinol oxidation by binding of cytochrome c in the Y132F and E272D enzymes indicate long range effects of these mutations.

  • A concerted, alternating sites mechanism of Ubiquinol oxidation by the dimeric cytochrome bc(1) complex.
    Biochimica et biophysica acta, 2002
    Co-Authors: Bernard L. Trumpower
    Abstract:

    A refinement of the protonmotive Q cycle mechanism is proposed in which oxidation of Ubiquinol is a concerted reaction and occurs by an alternating, half-of-the-sites mechanism. A concerted mechanism of Ubiquinol oxidation is inferred from the finding that there is reciprocal control between the high potential and low potential redox components involved in Ubiquinol oxidation. The potential of the Rieske iron-sulfur protein controls the rate of reduction of the b cytochromes, and the potential of the b cytochromes controls the rate of reduction of the Rieske protein and cytochrome c(1). A concerted mechanism of Ubiquinol oxidation reconciles the findings that the Ubiquinol-cytochrome c reductase kinetics of the bc(1) complex include both a pH dependence and a dependence on Rieske iron-sulfur protein midpoint potential.An alternating, half-of-the-sites mechanism for Ubiquinol oxidation is inferred from the finding that some inhibitory analogs of Ubiquinol that block Ubiquinol oxidation by binding to the Ubiquinol oxidation site in the bc(1) complex inhibit the yeast enzyme with a stoichiometry of 0.5 per bc(1) complex. One molecule of inhibitor is sufficient to fully inhibit the dimeric enzyme, and the binding is anti-cooperative, in that a second molecule of inhibitor binds with much lower affinity to a dimer in which an inhibitor molecule is already bound. An alternating, half-of-the-sites mechanism implies that, at least under some conditions, only half of the sites in the dimeric enzyme are reactive at any one time. This provides a raison d'être for the dimeric structure of the enzyme, in that bc(1) activity may be regulated and capable of switching between a half-of-the-sites active and a fully active enzyme.

  • A concerted, alternating sites mechanism of Ubiquinol oxidation by the dimeric cytochrome bc1 complex
    Biochimica et Biophysica Acta, 2002
    Co-Authors: Bernard L. Trumpower
    Abstract:

    Abstract A refinement of the protonmotive Q cycle mechanism is proposed in which oxidation of Ubiquinol is a concerted reaction and occurs by an alternating, half-of-the-sites mechanism. A concerted mechanism of Ubiquinol oxidation is inferred from the finding that there is reciprocal control between the high potential and low potential redox components involved in Ubiquinol oxidation. The potential of the Rieske iron–sulfur protein controls the rate of reduction of the b cytochromes, and the potential of the b cytochromes controls the rate of reduction of the Rieske protein and cytochrome c 1 . A concerted mechanism of Ubiquinol oxidation reconciles the findings that the Ubiquinol–cytochrome c reductase kinetics of the bc 1 complex include both a pH dependence and a dependence on Rieske iron–sulfur protein midpoint potential. An alternating, half-of-the-sites mechanism for Ubiquinol oxidation is inferred from the finding that some inhibitory analogs of Ubiquinol that block Ubiquinol oxidation by binding to the Ubiquinol oxidation site in the bc 1 complex inhibit the yeast enzyme with a stoichiometry of 0.5 per bc 1 complex. One molecule of inhibitor is sufficient to fully inhibit the dimeric enzyme, and the binding is anti-cooperative, in that a second molecule of inhibitor binds with much lower affinity to a dimer in which an inhibitor molecule is already bound. An alternating, half-of-the-sites mechanism implies that, at least under some conditions, only half of the sites in the dimeric enzyme are reactive at any one time. This provides a raison d'etre for the dimeric structure of the enzyme, in that bc 1 activity may be regulated and capable of switching between a half-of-the-sites active and a fully active enzyme.

  • A concerted, alternating sites mechanism of Ubiquinol oxidation by the dimeric cytochrome bc1 complex
    Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2002
    Co-Authors: Bernard L. Trumpower
    Abstract:

    AbstractA refinement of the protonmotive Q cycle mechanism is proposed in which oxidation of Ubiquinol is a concerted reaction and occurs by an alternating, half-of-the-sites mechanism. A concerted mechanism of Ubiquinol oxidation is inferred from the finding that there is reciprocal control between the high potential and low potential redox components involved in Ubiquinol oxidation. The potential of the Rieske iron–sulfur protein controls the rate of reduction of the b cytochromes, and the potential of the b cytochromes controls the rate of reduction of the Rieske protein and cytochrome c1. A concerted mechanism of Ubiquinol oxidation reconciles the findings that the Ubiquinol–cytochrome c reductase kinetics of the bc1 complex include both a pH dependence and a dependence on Rieske iron–sulfur protein midpoint potential.An alternating, half-of-the-sites mechanism for Ubiquinol oxidation is inferred from the finding that some inhibitory analogs of Ubiquinol that block Ubiquinol oxidation by binding to the Ubiquinol oxidation site in the bc1 complex inhibit the yeast enzyme with a stoichiometry of 0.5 per bc1 complex. One molecule of inhibitor is sufficient to fully inhibit the dimeric enzyme, and the binding is anti-cooperative, in that a second molecule of inhibitor binds with much lower affinity to a dimer in which an inhibitor molecule is already bound.An alternating, half-of-the-sites mechanism implies that, at least under some conditions, only half of the sites in the dimeric enzyme are reactive at any one time. This provides a raison d'être for the dimeric structure of the enzyme, in that bc1 activity may be regulated and capable of switching between a half-of-the-sites active and a fully active enzyme

  • Inhibitory Analogs of Ubiquinol Act Anti-cooperatively on the Yeast Cytochrome bc 1 Complex
    2002
    Co-Authors: Emma Berta Gutierrez-cirlos, Bernard L. Trumpower
    Abstract:

    The cytochrome bc1 complex is a dimeric enzyme that links electron transfer from Ubiquinol to cytochrome c by a protonmotive Q cycle mechanism in which Ubiquinol is oxidized at one center in the enzyme, referred to as center P, and ubiquinone is re-reduced at a second center, referred to as center N. To understand better the mechanism of Ubiquinol oxidation, we have examined the interaction of several inhibitory analogs of Ubiquinol with the yeast cytochrome bc1 complex. Stigmatellin and methoxyacrylate stilbene, two inhibitors that block Ubiquinol oxidation at center P, inhibit the yeast enzyme with a stoichiometry of 0.5 per bc1 complex, indicating that one molecule of inhibitor is sufficient to fully inhibit the dimeric enzyme. This stoichiometry was obtained when the inhibitors were titrated in cytochrome c reductase assays and in reactions of quinol with enzyme in which the inhibitors block pre-steady state reduction of cytochrome b. As an independent measure of inhibitor binding, we titrated the red shift in the optical spectrum of ferrocytochrome b with methoxyacrylate stilbene and thus confirmed the results of the inhibition of activity titrations. The titration curves also indicate that the binding is anti-cooperative, in that a second molecule of inhibitor binds with much lower affinity to a dimer in which an inhibitor molecule is already bound. Because these inhibitors bind to the Ubiquinol oxidation site in the bc1 complex, we propose that the yeast cytochrome bc1 complex oxidizes Ubiquinol by an alternating, half-of-the-sites mechanism.

Lester Packer - One of the best experts on this subject based on the ideXlab platform.

  • Assay of ubiquinones and Ubiquinols as antioxidants.
    Methods in Enzymology, 2004
    Co-Authors: Valerian E. Kagan, Elena Serbinova, Detcho A. Stoyanovsky, Sadie Khwaja, Lester Packer
    Abstract:

    Publisher Summary A diverse range of biological electron-transfer membranes are known to contain a complement of ubiquinones that can undergo redox changes. In membranes of animals, the role of ubiquinones in electron transport is unclear with the notable exception of ubiquinones in mitochondria. In mitochondria, ubiquinones act as mobile distributors of reducing equivalents among the NADH dehydrogenase, succinate dehydrogenase, and cytochrome b–c1 segment of the electron transport chain and as participants of the protonmotive Q cycle. Ubiquinones are stoichiometrically in excess of electron-transfer chains, additionally, ubiquinones in their reduced form, Ubiquinols, may act as free radical scavengers. In chemical systems, vitamin E (α-tocopherol) has a higher reactivity toward peroxyl radicals than Ubiquinols. The ubiquinone/Ubiquinol redox couple may act efficiently as a mediator in the regeneration of vitamin E by electron transport in cellular membranes. Ubiquinols may be necessary for reducing the vitamin E phenoxyl radical to prevent prooxidant effects of vitamin E in low density lipoproteins (LDL).

  • sensitive high performance liquid chromatography techniques for simultaneous determination of tocopherols tocotrienols Ubiquinols and ubiquinones in biological samples
    Methods in Enzymology, 1999
    Co-Authors: Maurizio Podda, R Milbradt, Maret G Traber, Christine Weber, Lester Packer
    Abstract:

    Publisher Summary Lipophilic antioxidants are responsible for the protection of cell membranes against lipid peroxidation. Vitamin E is the major lipophilic antioxidant in plasma, membranes, and tissues and is the collective name for the eight naturally occurring molecules (four tocopherols and four tocotrienols) that exhibit α-tocopherol activity. This chapter discusses the sensitive high-performance liquid chromatography techniques for simultaneous determination of tocopherols, tocotrienols, Ubiquinols, and ubiquinones in biological samples. The method described in this chapter allows the extraction and detection of the various vitamin E forms along with Ubiquinol/ubiquinone in a single aliquot of tissue. The unexpected distribution of vitamin E forms in different tissues exemplifies that the selective determination of the major lipophilic antioxidants is important for understanding the relationship among diet, oxidative stress, and cellular regulatory processes.

  • simultaneous determination of tissue tocopherols tocotrienols Ubiquinols and ubiquinones
    Journal of Lipid Research, 1996
    Co-Authors: Maurizio Podda, Maret G Traber, Christine Weber, Lester Packer
    Abstract:

    A tissue-specific distribution of the various vitamin E forms, tocotrienols and tocopherols, has been found, sug- gesting that these forms have unique roles in cellular func- tions. A sensitive procedure is described for the simultaneous determination of individual tocopherols, tocotrienols, ubiqui- nols, and ubiquinones using gradient high pressure liquid chromatography (HPLC) and electrochemical detection for vitamin E homologues and Ubiquinols, and in-line W detec- tion for ubiquinones. Using this method, the lipophilic anti- oxidant complement of a variety of hairless mouse tissues was analyzed. Of the vitamin E forms, brain contained virtually only a-tocopherol (5.4 k 0.1 nmol/g; 99.8%) and no detect- able tocotrienols were found. By contrast, skin contained nearly 15% tocotrienols and 1% y-tocopherol. In other tissues, the a-tocopherol content was higher (20 nmol/g), while each of the other forms represented about 1% of the total (ptoco- phero10.2 to 0.4 nmol/g, a-tocotrienol 0.1, ptocotrienolO.2). Ubiquinol-9 concentrations were highest in kidney (81 nmol/g) and in liver (42 nmol/g), while the highest ubiqui- none-9 concentrations were found in kidney (301 k 123 nmol/g) and heart (244 & 22 nmol/g). Liver contained nearly identical concentrations of each of the redox couple (ubiqui- nol-9 (41 k 16 nmovg) and ubiquinone-9 (46 k 18 nmol/g). I The unique distribution of these various antioxidants in the tissues measured suggests their distribution may be de- pendent upon selective mechanisms for maintaining antioxi- dant defenses in each tissue.-Podda, M., C. Weber, M. G. Traber, and L. Packer. Simultaneous determination of tissue tocopherol, tocotrienols, Ubiquinols, and ubiquinones. J. Lipid Res. 1996. 37: 893-901. Supplementary key words vitamin E coenzyme Q 0 HPLC 0 electrochemical detection tissue method

  • Simultaneous determination of tissue tocopherols, tocotrienols, Ubiquinols, and ubiquinones
    Journal of lipid research, 1996
    Co-Authors: Maurizio Podda, Maret G Traber, Christine Weber, Lester Packer
    Abstract:

    A tissue-specific distribution of the various vitamin E forms, tocotrienols and tocopherols, has been found, suggesting that these forms have unique roles in cellular functions. A sensitive procedure is described for the simultaneous determination of individual tocopherols, tocotrienols, Ubiquinols, and ubiquinones using gradient high pressure liquid chromatography (HPLC) and electrochemical detection for vitamin E homologues and Ubiquinols, and in-line UV detection for ubiquinones. Using this method, the lipophilic antioxidant complement of a variety of hairless mouse tissues was analyzed. Of the vitamin E forms, brain contained virtually only alpha-tocopherol (5.4 +/- 0.1 nmol/g; 99.8%) and no detectable tocotrienols were found. By contrast, skin contained nearly 15% tocotrienols and 1% gamma-tocopherol. In other tissues, the alpha-tocopherol content was higher (20 nmol/g), while each of the other forms represented about 1% of the total (gamma-tocopherol 0.2 to 0.4 nmol/g, alpha-tocotrienol 0.1, gamma-tocotrienol 0.2). Ubiquinol-9 concentrations were highest in kidney (81 nmol/g) and in liver (42 nmol/g), while the highest ubiquinone-9 concentrations were found in kidney (301 +/- 123 nmol/g) and heart (244 +/- 22 nmol/g). Liver contained nearly identical concentrations of each of the redox couple (Ubiquinol-9 (41 +/- 16 nmol/g) and ubiquinone-9 (46 +/- 18 nmol/g). The unique distribution of these various antioxidants in the tissues measured suggests their distribution may be dependent upon selective mechanisms for maintaining antioxidant defenses in each tissue.

  • Antioxidant action of Ubiquinol homologues with different isoprenoid chain length in biomembranes
    Free radical biology & medicine, 1990
    Co-Authors: Valerian E. Kagan, Elena Serbinova, Ginka M. Koynova, Stefka A. Kitanova, Vladimir A. Tyurin, Tsanko S. Stoytchev, Peter J. Quinn, Lester Packer
    Abstract:

    Ubiquinones (CoQn) are intrinsic lipid components of many membranes. Besides their role in electron-transfer reactions they may act as free radical scavengers, yet their antioxidant function has received relatively little study. The efficiency of Ubiquinols of varying isoprenoid chain length (from Q0 to Q10) in preventing (Fe2+ + ascorbate)-dependent or (Fe2+ + NADPH)-dependent lipid peroxidation was investigated in rat liver microsomes and brain synaptosomes and mitochondria. Ubiquinols, the reduced forms of CoQn, possess much greater antioxidant activity than the oxidized ubiquinone forms. In homogenous solution the radical scavenging activity of Ubiquinol homologues does not depend on the length of their isoprenoid chain. However in membranes Ubiquinols with short isoprenoid chains (Q1–Q4) are much more potent inhibitors of lipid peroxidation than the longer chain homologues (Q5–Q10). It is found that: i) the inhibitory action, that is, antioxidant efficiency of short-chain Ubiquinols decreases in order Q1 > Q2 > Q3 > Q4; ii) the antioxidant efficiency of long-chain Ubiquinols is only slightly dependent on their concentrations in the order Q5 > Q6 > Q7 > Q8 > Q9 > Q10 and iii) the antioxidant efficiency of Q0 is markedly less than that of other homologues. Interaction of Ubiquinols with oxygen radicals was followed by their effects on luminol-activated chemiluminescence. Ubiquinols Q1–Q4 at 0.1 mM completely inhibit the luminol-activated NADPH-dependent chemiluminescent response of microsomes, while homologues Q6–Q10 exert no effect. In contrast to Ubiquinol Q10 (ubiquinone Q10) ubiquinone Q1 synergistically enhances NADPH-dependent regeneration of endogenous vitamin E in microsomes thus providing for higher antioxidant protection against lipid peroxidation. The differences in the antioxidant potency of Ubiquinols in membranes are suggested to result from differences in partitioning into membranes, intramembrane mobility and non-uniform distribution of Ubiquinols resulting in differing efficiency of interaction with oxygen and lipid radicals as well as different efficiency of Ubiquinols in regeneration of endogenous vitamin E.

Laura Landi - One of the best experts on this subject based on the ideXlab platform.

  • Autoxidation and antioxidant activity of Ubiquinol homologues in large unilamellar vesicles
    Chemistry and physics of lipids, 1994
    Co-Authors: Marta Cipollone, Diana Fiorentini, Maria Cristina Galli, Laura Landi
    Abstract:

    The antioxidant activity of Ubiquinol homologues with different side-chain length such as Ubiquinol-3 and Ubiquinol-7 was compared with that of alpha-tocopherol when peroxidation was induced by the water-soluble initiator 2,2'-azobis-(2-amidinopropane hydrochloride). In large unilamellar vesicles containing equal amounts of alpha-tocopherol, Ubiquinol-3 and Ubiquinol-7 the rates of inhibition were very similar but the stoichiometric factor of quinols was approximately 1. To explain this low value, which is one-half of that found when the autoxidation was performed in apolar solvents (Chem. Phys. Lipids (1992) 61, 121-130), the oxidation of alpha-tocopherol and Ubiquinol-3 initiated by the azocompound was studied both in methanol and in dimiristoyl-lecithin vesicles. The results obtained show that the Ubiquinol homologues undergo a radical chain reaction taking place at the polar interface and suggest that the average preferred location of both quinol headgroups is near to the outer surface of the bilayer.

  • Ubiquinol-3 and Ubiquinol-7 Exhibit Similar Antioxidant Activity in Model Membranes
    Free radical research communications, 1993
    Co-Authors: Diana Fiorentini, Luciana Cabrini, Laura Landi
    Abstract:

    This study was undertaken to compare, on a kinetic basis, the antioxidant efficiency of an Ubiquinol homologue having a short isoprenoid side-chain length, such as Ubiquinol-3, with that of the long chain Ubiquinol-7, by determining their rate constants of inhibition with respect to alpha-tocopherol. To this purpose we incorporated Ubiquinol-3, or Ubiquinol-7, or alpha-tocopherol into liposomes of egg yolk lecithin, and triggered lipid peroxidation with the thermal decomposition of a lipophilic azocompound. The results show that: i) the rate constants of inhibition for the two quinols are similar and slightly lower than that of alpha-tocopherol; ii) the length of the radical chain obtained in the presence of the two quinols is almost the same. From these data we concluded that the two homologues tested behave as chain-breaking antioxidants with quite similar effectiveness.

  • The antioxidant activity of Ubiquinol-3 in homogeneous solution and in liposomes.
    Chemistry and physics of lipids, 1992
    Co-Authors: Laura Landi, Claudio Stefanelli, Luciana Cabrini, Diana Fiorentini, Gian Franco Pedulli
    Abstract:

    Abstract With a view to determining the antioxidant effectiveness of Ubiquinol, the autoxidation of egg phosphatidylcholine initiated by an azocompound was studied both in homogeneous solution and in liposomes, either in the presence or in the absence of Ubiquinol-3. The results show that Ubiquinol behaves as a chain-breaking antioxidant by trapping lipid peroxyl radicals, its inhibition rate constant being about one half of that of α-tocopherol in both systems under investigation. In organic solvents the stoichiometric factor was found approx. 2 and in liposomes approx. 0.5, i.e. one fourth of that of α-tocopherol. We suggest that the lower value found in model membranes is due to autoxidation of the quinol itself by a radical chain reaction taking place at the polar interface. Ubiquinol-3 exhibits a sparing effect toward α-tocopherol, both in liposomes and in tert -butanol. It is suggested, on a thermodynamic basis, that the regeneration of vitamin E from the corresponding radical is more likely to occur by reaction with the ubisemiquinone rather than with the Ubiquinol. Although these results, obtained in in vitro systems, can not be directly extrapolated to an in vivo system, they may be useful to clarify the antioxidant role of Ubiquinol in biomembranes.

  • Ubiquinol PREVENTS ALPHA -TOCOPHEROL CONSUMPTION DURING LIPOSOME PEROXIDATION
    Biochemistry international, 1991
    Co-Authors: Luciana Cabrini, Fiorentini D, Claudio Stefanelli, Laura Landi
    Abstract:

    In this study we investigated whether alpha-tocopherol can be spared by Ubiquinol-3 during autoxidation of multilamellar liposome. A lipophilic azocompound, 2,2'-azobis-(2,4-dimethyl-valeronitrile), was chosen to initiate liposome autoxidation. The effect of either alpha-tocopherol, Ubiquinol-3, or a mixture of them was compared. Rates of conjugated diene formation and concomitant disappearance of the two antioxidants was measured. Since the inhibition rate constant for the scavenging of peroxyl radical for alpha-tocopherol was higher than that for quinol-3, it was concluded that alpha-tocopherol is regenerated by Ubiquinol-3.

Maurizio Podda - One of the best experts on this subject based on the ideXlab platform.

  • sensitive high performance liquid chromatography techniques for simultaneous determination of tocopherols tocotrienols Ubiquinols and ubiquinones in biological samples
    Methods in Enzymology, 1999
    Co-Authors: Maurizio Podda, R Milbradt, Maret G Traber, Christine Weber, Lester Packer
    Abstract:

    Publisher Summary Lipophilic antioxidants are responsible for the protection of cell membranes against lipid peroxidation. Vitamin E is the major lipophilic antioxidant in plasma, membranes, and tissues and is the collective name for the eight naturally occurring molecules (four tocopherols and four tocotrienols) that exhibit α-tocopherol activity. This chapter discusses the sensitive high-performance liquid chromatography techniques for simultaneous determination of tocopherols, tocotrienols, Ubiquinols, and ubiquinones in biological samples. The method described in this chapter allows the extraction and detection of the various vitamin E forms along with Ubiquinol/ubiquinone in a single aliquot of tissue. The unexpected distribution of vitamin E forms in different tissues exemplifies that the selective determination of the major lipophilic antioxidants is important for understanding the relationship among diet, oxidative stress, and cellular regulatory processes.

  • simultaneous determination of tissue tocopherols tocotrienols Ubiquinols and ubiquinones
    Journal of Lipid Research, 1996
    Co-Authors: Maurizio Podda, Maret G Traber, Christine Weber, Lester Packer
    Abstract:

    A tissue-specific distribution of the various vitamin E forms, tocotrienols and tocopherols, has been found, sug- gesting that these forms have unique roles in cellular func- tions. A sensitive procedure is described for the simultaneous determination of individual tocopherols, tocotrienols, ubiqui- nols, and ubiquinones using gradient high pressure liquid chromatography (HPLC) and electrochemical detection for vitamin E homologues and Ubiquinols, and in-line W detec- tion for ubiquinones. Using this method, the lipophilic anti- oxidant complement of a variety of hairless mouse tissues was analyzed. Of the vitamin E forms, brain contained virtually only a-tocopherol (5.4 k 0.1 nmol/g; 99.8%) and no detect- able tocotrienols were found. By contrast, skin contained nearly 15% tocotrienols and 1% y-tocopherol. In other tissues, the a-tocopherol content was higher (20 nmol/g), while each of the other forms represented about 1% of the total (ptoco- phero10.2 to 0.4 nmol/g, a-tocotrienol 0.1, ptocotrienolO.2). Ubiquinol-9 concentrations were highest in kidney (81 nmol/g) and in liver (42 nmol/g), while the highest ubiqui- none-9 concentrations were found in kidney (301 k 123 nmol/g) and heart (244 & 22 nmol/g). Liver contained nearly identical concentrations of each of the redox couple (ubiqui- nol-9 (41 k 16 nmovg) and ubiquinone-9 (46 k 18 nmol/g). I The unique distribution of these various antioxidants in the tissues measured suggests their distribution may be de- pendent upon selective mechanisms for maintaining antioxi- dant defenses in each tissue.-Podda, M., C. Weber, M. G. Traber, and L. Packer. Simultaneous determination of tissue tocopherol, tocotrienols, Ubiquinols, and ubiquinones. J. Lipid Res. 1996. 37: 893-901. Supplementary key words vitamin E coenzyme Q 0 HPLC 0 electrochemical detection tissue method

  • Simultaneous determination of tissue tocopherols, tocotrienols, Ubiquinols, and ubiquinones
    Journal of lipid research, 1996
    Co-Authors: Maurizio Podda, Maret G Traber, Christine Weber, Lester Packer
    Abstract:

    A tissue-specific distribution of the various vitamin E forms, tocotrienols and tocopherols, has been found, suggesting that these forms have unique roles in cellular functions. A sensitive procedure is described for the simultaneous determination of individual tocopherols, tocotrienols, Ubiquinols, and ubiquinones using gradient high pressure liquid chromatography (HPLC) and electrochemical detection for vitamin E homologues and Ubiquinols, and in-line UV detection for ubiquinones. Using this method, the lipophilic antioxidant complement of a variety of hairless mouse tissues was analyzed. Of the vitamin E forms, brain contained virtually only alpha-tocopherol (5.4 +/- 0.1 nmol/g; 99.8%) and no detectable tocotrienols were found. By contrast, skin contained nearly 15% tocotrienols and 1% gamma-tocopherol. In other tissues, the alpha-tocopherol content was higher (20 nmol/g), while each of the other forms represented about 1% of the total (gamma-tocopherol 0.2 to 0.4 nmol/g, alpha-tocotrienol 0.1, gamma-tocotrienol 0.2). Ubiquinol-9 concentrations were highest in kidney (81 nmol/g) and in liver (42 nmol/g), while the highest ubiquinone-9 concentrations were found in kidney (301 +/- 123 nmol/g) and heart (244 +/- 22 nmol/g). Liver contained nearly identical concentrations of each of the redox couple (Ubiquinol-9 (41 +/- 16 nmol/g) and ubiquinone-9 (46 +/- 18 nmol/g). The unique distribution of these various antioxidants in the tissues measured suggests their distribution may be dependent upon selective mechanisms for maintaining antioxidant defenses in each tissue.

Maret G Traber - One of the best experts on this subject based on the ideXlab platform.

  • sensitive high performance liquid chromatography techniques for simultaneous determination of tocopherols tocotrienols Ubiquinols and ubiquinones in biological samples
    Methods in Enzymology, 1999
    Co-Authors: Maurizio Podda, R Milbradt, Maret G Traber, Christine Weber, Lester Packer
    Abstract:

    Publisher Summary Lipophilic antioxidants are responsible for the protection of cell membranes against lipid peroxidation. Vitamin E is the major lipophilic antioxidant in plasma, membranes, and tissues and is the collective name for the eight naturally occurring molecules (four tocopherols and four tocotrienols) that exhibit α-tocopherol activity. This chapter discusses the sensitive high-performance liquid chromatography techniques for simultaneous determination of tocopherols, tocotrienols, Ubiquinols, and ubiquinones in biological samples. The method described in this chapter allows the extraction and detection of the various vitamin E forms along with Ubiquinol/ubiquinone in a single aliquot of tissue. The unexpected distribution of vitamin E forms in different tissues exemplifies that the selective determination of the major lipophilic antioxidants is important for understanding the relationship among diet, oxidative stress, and cellular regulatory processes.

  • simultaneous determination of tissue tocopherols tocotrienols Ubiquinols and ubiquinones
    Journal of Lipid Research, 1996
    Co-Authors: Maurizio Podda, Maret G Traber, Christine Weber, Lester Packer
    Abstract:

    A tissue-specific distribution of the various vitamin E forms, tocotrienols and tocopherols, has been found, sug- gesting that these forms have unique roles in cellular func- tions. A sensitive procedure is described for the simultaneous determination of individual tocopherols, tocotrienols, ubiqui- nols, and ubiquinones using gradient high pressure liquid chromatography (HPLC) and electrochemical detection for vitamin E homologues and Ubiquinols, and in-line W detec- tion for ubiquinones. Using this method, the lipophilic anti- oxidant complement of a variety of hairless mouse tissues was analyzed. Of the vitamin E forms, brain contained virtually only a-tocopherol (5.4 k 0.1 nmol/g; 99.8%) and no detect- able tocotrienols were found. By contrast, skin contained nearly 15% tocotrienols and 1% y-tocopherol. In other tissues, the a-tocopherol content was higher (20 nmol/g), while each of the other forms represented about 1% of the total (ptoco- phero10.2 to 0.4 nmol/g, a-tocotrienol 0.1, ptocotrienolO.2). Ubiquinol-9 concentrations were highest in kidney (81 nmol/g) and in liver (42 nmol/g), while the highest ubiqui- none-9 concentrations were found in kidney (301 k 123 nmol/g) and heart (244 & 22 nmol/g). Liver contained nearly identical concentrations of each of the redox couple (ubiqui- nol-9 (41 k 16 nmovg) and ubiquinone-9 (46 k 18 nmol/g). I The unique distribution of these various antioxidants in the tissues measured suggests their distribution may be de- pendent upon selective mechanisms for maintaining antioxi- dant defenses in each tissue.-Podda, M., C. Weber, M. G. Traber, and L. Packer. Simultaneous determination of tissue tocopherol, tocotrienols, Ubiquinols, and ubiquinones. J. Lipid Res. 1996. 37: 893-901. Supplementary key words vitamin E coenzyme Q 0 HPLC 0 electrochemical detection tissue method

  • Simultaneous determination of tissue tocopherols, tocotrienols, Ubiquinols, and ubiquinones
    Journal of lipid research, 1996
    Co-Authors: Maurizio Podda, Maret G Traber, Christine Weber, Lester Packer
    Abstract:

    A tissue-specific distribution of the various vitamin E forms, tocotrienols and tocopherols, has been found, suggesting that these forms have unique roles in cellular functions. A sensitive procedure is described for the simultaneous determination of individual tocopherols, tocotrienols, Ubiquinols, and ubiquinones using gradient high pressure liquid chromatography (HPLC) and electrochemical detection for vitamin E homologues and Ubiquinols, and in-line UV detection for ubiquinones. Using this method, the lipophilic antioxidant complement of a variety of hairless mouse tissues was analyzed. Of the vitamin E forms, brain contained virtually only alpha-tocopherol (5.4 +/- 0.1 nmol/g; 99.8%) and no detectable tocotrienols were found. By contrast, skin contained nearly 15% tocotrienols and 1% gamma-tocopherol. In other tissues, the alpha-tocopherol content was higher (20 nmol/g), while each of the other forms represented about 1% of the total (gamma-tocopherol 0.2 to 0.4 nmol/g, alpha-tocotrienol 0.1, gamma-tocotrienol 0.2). Ubiquinol-9 concentrations were highest in kidney (81 nmol/g) and in liver (42 nmol/g), while the highest ubiquinone-9 concentrations were found in kidney (301 +/- 123 nmol/g) and heart (244 +/- 22 nmol/g). Liver contained nearly identical concentrations of each of the redox couple (Ubiquinol-9 (41 +/- 16 nmol/g) and ubiquinone-9 (46 +/- 18 nmol/g). The unique distribution of these various antioxidants in the tissues measured suggests their distribution may be dependent upon selective mechanisms for maintaining antioxidant defenses in each tissue.