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Food Chemistry May 2022Suppressing toxic aldehydic lipid oxidation product (LOP) generation in culinary oils is now considered vital, since the deleterious effects arising from their ingestion...
Suppressing toxic aldehydic lipid oxidation product (LOP) generation in culinary oils is now considered vital, since the deleterious effects arising from their ingestion are implicated in a wide range of disease conditions. Partial substitution involves the replenishment of thermally-stressed culinary oils with corresponding unheated ones. This technique was tested by employing 10%, 25%, 50%, and 75% (v/v) partial substitutions of coconut, olive, rapeseed, and sunflower oils at 180℃ for a 300 min continuous thermo-oxidation duration. Oil samples were analysed by proton nuclear magnetic resonance (H NMR) spectroscopy. Trace metal levels, including oxidation-reduction (redox)-active metal ions credited with enhancing cooking oil oxidation were also analysed using inductively coupled plasma-optical emission spectroscopy (ICP-OES). As expected, the degree of oil unsaturation, and the % partial substitutions significantly influenced their susceptibility to thermo-oxidation. In view of the very low polyunsaturated fatty acid (PUFA) and monounsaturated fatty acid (MUFA) contents of coconut oil, both the class and concentrations of evolved LOPs were found to be least affected by this partial substitution process. Aldehydic LOPs were greatly suppressed in partially-substituted rapeseed oil. The % suppression activity of LOPs evaluated for the partially substituted oils were generally high making partial oil substitutions an effective chemical-free method in suppressing LOPs at both industrial and commercial levels. In general, the % partial oil substitutions were directly related to the dilution effect observed for LOPs quantified in the oils. Furthermore, trace metal ion concentrations measured in the culinary oils did not influence the evolution of LOPs in the oils.
Topics: Dietary Fats, Unsaturated; Ions; Lipid Peroxidation; Oils; Olive Oil; Oxidation-Reduction; Plant Oils; Sunflower Oil
PubMed: 34920305
DOI: 10.1016/j.foodchem.2021.131823 -
Biomaterials Nov 2006We developed a radiation cross-linked ultra-high molecular weight polyethylene (UHMWPE) stabilized with alpha-tocopherol (Vitamin E) as a bearing material in total joint...
We developed a radiation cross-linked ultra-high molecular weight polyethylene (UHMWPE) stabilized with alpha-tocopherol (Vitamin E) as a bearing material in total joint replacements. The stabilizing effect of alpha-tocopherol on free radical reactions in UHMWPE is not well understood. We investigated the effect of alpha-tocopherol on the oxidation and transformation of residual free radicals during real-time aging of alpha-tocopherol-doped, irradiated UHMWPE (alphaTPE) and irradiated UHMWPE (control). Samples were aged at 22 degrees C (room temperature) in air, at 40 degrees C in air and at 40 degrees C in water for 7 months. During the first month, alphaTPE showed some oxidation at the surface, which stayed constant thereafter. Control exhibited substantial oxidation in the subsurface region, which increased with time. The alkyl/allyl free radicals transformed to oxygen centered ones in both materials; this transformation occurred faster in alpha-TPE. In summary, the real-time oxidation behavior of alpha-TPE was consistent with that observed using accelerated aging methods. This new UHMWPE is oxidation resistant and is expected to maintain its properties in the long term.
Topics: Electron Spin Resonance Spectroscopy; Free Radicals; Hydrogen Peroxide; Molecular Structure; Oxidation-Reduction; Polyethylenes; Temperature; alpha-Tocopherol
PubMed: 16887182
DOI: 10.1016/j.biomaterials.2006.07.017 -
The Journal of Biological Chemistry Jul 1978The oxidation-reduction potential values for the two electron transfers to glucose oxidase were obtained at pH 5.3, where the neutral radical is the stable form, and at...
The oxidation-reduction potential values for the two electron transfers to glucose oxidase were obtained at pH 5.3, where the neutral radical is the stable form, and at pH 9.3, where the anion radical is the stable form. The midpoint potentials at 25 degrees were: pH 5.3 EFl1ox + e- H+ equilibrium EFlH. Em1 = -0.063 +/- 0.011 V EFlH. + e- + H+ equilibrium EFlredH2 Em2 = -0.065 +/- 0.007 V pH 9.3 EFlox + e- EFi- Em1 = -0.200 +/- 0.010 V EFi- + e- + H+ equilibrium EFlredH- Em2 = -0.240 +/- 0.005 V All potentials were measured versus the standard hydrogen electrode (SHE). The potentials indicated that glucose oxidase radicals are stabilized by kinetic factors and not by thermodynamic energy barriers. The pK for the glucose oxidase radical was 7.28 from dead time stopped flow measurements and the extinction coefficient of the neutral semiquinone was 4140 M-1 cm-1 at 570 nm. Both radical forms reacted with oxygen in a second order fashion. The rate at 25 degrees for the neutral semiquinone was 1.4 X 10(4) M-1 s-1; that for the anion radical was 3.5 X 10(4) M-1 s-1. The rate of oxidation of the neutral radical changed by a factor of 9 for a temperature difference of 22 degrees. For the anion radical, the oxidation rate changed by a factor of 6 for a 22 degrees change in temperature. We studied the oxygen reactivity of the 2-electron reduced form of the enzyme over a wide wavelength range and failed to detect either oxygenated flavin derivatives or semiquinoid forms as intermediates. The rate of reoxidation of fully reduced glucose oxidase at pH 9.3 was dependent on ionic strength.
Topics: Aspergillus niger; Electron Transport; Glucose Oxidase; Hydrogen-Ion Concentration; Kinetics; Oxidation-Reduction; Oxygen; Potentiometry; Spectrophotometry
PubMed: 27511
DOI: No ID Found -
Redox Biology Aug 2021
Topics: Achievement; Awards and Prizes; Biology; Oxidation-Reduction
PubMed: 34052599
DOI: 10.1016/j.redox.2021.102019 -
Antioxidants & Redox Signaling May 2014This Editorial has the intention to stress the complex chemistry and biology of redox-active compounds, regarded as SOD mimics. It further aims to caution the...
This Editorial has the intention to stress the complex chemistry and biology of redox-active compounds, regarded as SOD mimics. It further aims to caution the researchers of the importance of being up-to-date with the present knowledge on such compounds and their cellular redox biology when coming up with their conclusions, based on the particular species involved in their studies.
Topics: Animals; Humans; Molecular Mimicry; Oxidation-Reduction; Signal Transduction; Superoxide Dismutase
PubMed: 24650329
DOI: 10.1089/ars.2014.5921 -
Oxidative Medicine and Cellular... 2010Dizocilpine (MK-801), an extensively investigated drug possessing secondary amine and benzenoid functions, displays a wide array of biological properties, including... (Review)
Review
Dizocilpine (MK-801), an extensively investigated drug possessing secondary amine and benzenoid functions, displays a wide array of biological properties, including anticonvulsant and anesthetic. There is scant discussion of biomechanism. A relevant, important finding is formation of oxidative metabolites in the hydroxylamine and phenolic categories. Analogy to cocaine metabolites suggests participation of redox entities, such as, hydroxylamine, nitroxide and nitrosonium, which can lead to electron transfer and radical formation. There is also similarity to metabolism by 3,3'-iminodipropionitrile and phencyclidine. Alternatively, the phenolic metabolites are well-known precursors of ET quinones. The review documents various physiological effects, mainly involving the central nervous system. Also of interest are the pro- and ant-oxidant properties. Considerable attention has been paid to MK-801 as an antagonist of the N-methyl-D-aspartate receptor in the glutamate category. This aspect is often associated with effects on the central nervous system. The review also provides recent literature dealing with MK-801/NMDA receptor in various areas of bioactivity. Studies were made of MK-801 involvement in working memory processing. Deficits in behavior were noted after administration of the drug. Treatment of mice with dizocilpine induced learning impairment. The influence of MK-801 on fear has been investigated. The substance is known to exert an analgesic effect in pain control. A number of reports deal with anesthetic properties.
Topics: Animals; Circadian Rhythm; Dizocilpine Maleate; Electron Transport; Excitatory Amino Acid Antagonists; Humans; Mice; Oxidation-Reduction
PubMed: 20716924
DOI: 10.4161/oxim.3.1.10028 -
European Journal of Biochemistry Mar 1988The direct electrochemistry of redox proteins has been achieved at a variety of electrodes, including modified gold, pyrolytic graphite and metal oxides. Careful design... (Review)
Review
The direct electrochemistry of redox proteins has been achieved at a variety of electrodes, including modified gold, pyrolytic graphite and metal oxides. Careful design of electrode surfaces and electrolyte conditions are required for the attainment of rapid and reversible protein-electrode interaction. The electron transfer reactions of more complex systems, such as redox enzymes, are now being examined. The 'well-behaved' electrochemistry of redox proteins can be usefully exploited by coupling the electrode reaction to enzymes for which the redox proteins act as cofactors. In systems where direct electron transfer is very slow, small electron carriers, or mediators, may be employed to enhance the rate of electron exchange with the electrode. The organometallic compound ferrocene and its derivatives have proved particularly effective in this role. A new generation of electrochemical biosensors employs ferrocene derivatives as mediators.
Topics: Electrodes; Electron Transport; Models, Chemical; Oxidation-Reduction; Proteins
PubMed: 3280307
DOI: 10.1111/j.1432-1033.1988.tb13882.x -
The Analyst Aug 2016The reduction and oxidation of the flavin system is an important electron transfer reaction in biological systems. Several reaction pathways exist to connect oxidized to...
The reduction and oxidation of the flavin system is an important electron transfer reaction in biological systems. Several reaction pathways exist to connect oxidized to fully reduced riboflavin, each with unique intermediates including a semi-quinone radical. By performing surface-enhanced Raman scattering (SERS) with simultaneous electrochemical detection of riboflavin at different pH values, we are able to correlate reversible changes in spectral features to the current changes observed in the cyclic voltammetry. Multivariate curve resolution analysis of the SERS spectra indicates that three distinct components were present at the SERS electrode at each pH during the potential sweep. To verify and better understand the variations in Raman bands across the voltammogram, density functional theory (DFT) calculations were performed to model the effect of pH and oxidation state on the riboflavin Raman spectrum. The calculated spectra show qualitative agreement with the species identified in the chemometric analysis. This combination of results indicates the presence of the oxidized, semi-quinone, and reduced forms of riboflavin and provides insight into the mechanism of the flavin redox system.
Topics: Electrodes; Electron Transport; Oxidation-Reduction; Riboflavin; Spectrum Analysis, Raman
PubMed: 27297697
DOI: 10.1039/c6an01054g -
The Biochemical Journal May 1984Potentiometric titrations of pig liver electron-transfer flavoprotein (ETF) were performed at pH 7.5 and 4 degrees C, both in the reductive and oxidative directions....
Potentiometric titrations of pig liver electron-transfer flavoprotein (ETF) were performed at pH 7.5 and 4 degrees C, both in the reductive and oxidative directions. Reduction of ETF to the hydroquinone form required a total of two reducing equivalents/mol of ETF with the formation of sub-stoichiometric amounts of anionic semiquinone as an intermediate. The oxidation-reduction potentials for the two one-electron couples, oxidized ETF/ETF semiquinone and ETF semiquinone/fully reduced ETF, are +4 mV and -50 mV respectively. The overall midpoint potential for the two-electron couple (oxidized ETF/fully reduced ETF) is -23 mV.
Topics: Animals; Electron Transport; Electron-Transferring Flavoproteins; Flavoproteins; Mitochondria, Liver; Oxidation-Reduction; Potentiometry; Quinones; Swine
PubMed: 6743239
DOI: 10.1042/bj2191043 -
Journal of Computational Chemistry Mar 2013The oxidation-reduction potentials of electron transfer proteins determine the driving forces for their electron transfer reactions. Although the type of redox site...
The oxidation-reduction potentials of electron transfer proteins determine the driving forces for their electron transfer reactions. Although the type of redox site determines the intrinsic energy required to add or remove an electron, the electrostatic interaction energy between the redox site and its surrounding environment can greatly shift the redox potentials. Here, a method for calculating the reduction potential versus the standard hydrogen electrode, E°, of a metalloprotein using a combination of density functional theory and continuum electrostatics is presented. This work focuses on the methodology for the continuum electrostatics calculations, including various factors that may affect the accuracy. The calculations are demonstrated using crystal structures of six homologous HiPIPs, which give E° that are in excellent agreement with experimental results.
Topics: Electron Transport; Iron-Sulfur Proteins; Models, Molecular; Molecular Structure; Oxidation-Reduction; Quantum Theory; Thermodynamics
PubMed: 23115132
DOI: 10.1002/jcc.23169