The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Alexander I. Kotelnikov - One of the best experts on this subject based on the ideXlab platform.
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Enzyme-like effect of Metmyoglobin on the thermal cis-trans isomerization of stilbazolium betaine
Journal of Biological Inorganic Chemistry, 2000Co-Authors: Alexander V. Pastukhov, Vitalii R. Vogel, Alexander I. KotelnikovAbstract:A photochromic compound, stilbazolium betaine M, when associated with Metmyoglobin undergoes an accelerated thermal cis→trans isomerization. A study of the pH and ionic strength dependence of the isomerization reaction rate of the photochrome associated with Metmyoglobin was perfomed. A comparative investigation of the reaction carried out in the presence of three proteins, Metmyoglobin, apomyoglobin, and human albumin, indicates a specific influence of the heme pocket environment on the reaction. Possible mechanisms of the reaction acceleration are considered.
Alexander V. Pastukhov - One of the best experts on this subject based on the ideXlab platform.
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Enzyme-like effect of Metmyoglobin on the thermal cis-trans isomerization of stilbazolium betaine
Journal of Biological Inorganic Chemistry, 2000Co-Authors: Alexander V. Pastukhov, Vitalii R. Vogel, Alexander I. KotelnikovAbstract:A photochromic compound, stilbazolium betaine M, when associated with Metmyoglobin undergoes an accelerated thermal cis→trans isomerization. A study of the pH and ionic strength dependence of the isomerization reaction rate of the photochrome associated with Metmyoglobin was perfomed. A comparative investigation of the reaction carried out in the presence of three proteins, Metmyoglobin, apomyoglobin, and human albumin, indicates a specific influence of the heme pocket environment on the reaction. Possible mechanisms of the reaction acceleration are considered.
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Catalysis of the Back Thermal cis–trans Isomerization Reaction of Stilbazolium Betaine by Metmyoglobin
Journal of Fluorescence, 1999Co-Authors: Vitalii R. Vogel, Alexander V. Pastukhov, A. I. Kotel’nikovAbstract:The catalytic effect of Metmyoglobin on the back thermal cis → trans isomerization reaction of stilbazolium betaine M is reported. This reaction shows substantial acceleration in the presence of Metmyoglobin in comparison to the same reaction without the protein or in the presence of Metmyoglobin cyanide. It is suggested that the observed thermal reaction acceleration may arise from the coordination of the protonated stilbazolium betaine molecule to the sixth ligand position of the heme iron and subsequent chromophore deprotonation or from the low polarity of the heme pocket microenvironment.
R Ramanathan - One of the best experts on this subject based on the ideXlab platform.
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carbon chain length of lipid oxidation products influence lactate dehydrogenase and nadh dependent Metmyoglobin reductase activity
Journal of Agricultural and Food Chemistry, 2019Co-Authors: Chaoyu Zhai, R Ramanathan, Kiefer Peckham, K E Belk, M N NairAbstract:The biochemical basis of lower Metmyoglobin reducing activity (MRA) in high-oxygen modified atmospheric packaged (HiOx-MAP) beef than those in vacuum and polyvinyl chloride (PVC) packaging is not clear. To explore this, the effects of lipid oxidation products with varying carbon chain length on lactate dehydrogenase (LDH) and NADH-dependent Metmyoglobin reductase activity were evaluated. Surface color, MRA, and lipid oxidation of beef longissimus lumborum steaks (n = 10) were measured during 6-day display. Further, two enzymes, LDH and NADH-dependent Metmyoglobin reductase (n = 5), critical for MRA were incubated with or without (control) lipid oxidation products of varying carbon chain length: malondialdehyde (3-carbon), hexenal (6-carbon), and 4-hydroxynonenal (9-carbon). Steaks in HiOx-MAP had greater (P < 0.05) redness than vacuum and PVC, but had lower (P < 0.05) MRA and greater (P < 0.05) lipid oxidation on day 6. LDH and NADH-dependent Metmyoglobin reductase activities were differentially influence...
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species specific effects on non enzymatic Metmyoglobin reduction in vitro
Meat Science, 2015Co-Authors: N N Elroy, Janet Rogers, G G Mafi, D L Vanoverbeke, Steven D Hartson, R RamanathanAbstract:Abstract Our objectives were to determine the non-enzymatic Metmyoglobin reduction properties of bovine, porcine, and equine myoglobins and to characterize the effects of pre-incubation of 4-hydroxy-2-nonenal (HNE) with myoglobins on non-enzymatic Metmyoglobin reduction in vitro. Purified bovine, porcine, and equine Metmyoglobins (0.05 mM) were reduced at pH 5.6 and 7.4 in the presence or absence of HNE. Rates of Metmyoglobin reduction were monitored by spectrophotometry, and myoglobin adducts were characterized by high-resolution mass-spectrometry. Results showed that the species origins of individual myoglobins determined rates of non-enzymatic reduction (beef > equine > pork; P
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reverse electron transport effects on nadh formation and Metmyoglobin reduction
Meat Science, 2015Co-Authors: K Belskie, R Ramanathan, C B Van Buiten, R A ManciniAbstract:Abstract The objective was to determine if NADH generated via reverse electron flow in beef mitochondria can be used for electron transport-mediated reduction and Metmyoglobin reductase pathways. Beef mitochondria were isolated from bovine hearts (n = 5) and reacted with combinations of succinate, NAD, and mitochondrial inhibitors to measure oxygen consumption and NADH formation. Mitochondria and Metmyoglobin were reacted with succinate, NAD, and mitochondrial inhibitors to measure electron transport-mediated Metmyoglobin reduction and Metmyoglobin reductase activity. Addition of succinate and NAD increased oxygen consumption, NADH formation, electron transport-mediated Metmyoglobin reduction, and reductase activity (p
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covalent binding of 4 hydroxy 2 nonenal to lactate dehydrogenase decreases nadh formation and Metmyoglobin reducing activity
Journal of Agricultural and Food Chemistry, 2014Co-Authors: R Ramanathan, R A Mancini, S P Suman, C M BeachAbstract:Lactate dehydrogenase (LDH) activity can regenerate NADH, which is a critical component in Metmyoglobin reduction. However, limited research has determined the effects of lipid oxidation products o...
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effects of lactate on ground lamb colour stability and mitochondria mediated Metmyoglobin reduction
Food Chemistry, 2011Co-Authors: R Ramanathan, R A Mancini, P Joseph, Nantawat Tatiyaborworntham, Katherine H Petersson, M K R KondaAbstract:Abstract Previous research suggests that lactate’s colour stabilizing effect in beef is through NADH production and antioxidant activity. However, no research has assessed lactate’s role in lamb colour. Hence, our objectives were to evaluate the effects of lactate on lamb surface discolouration, oxygen consumption, and Metmyoglobin reduction. In experiment 1, lactate (final meat concentration = 2.5% w/w) was added to ground lamb (n = 20 carcasses) and patties were stored for 3 days at 1 °C in PVC packaging. Surface colour (CIE L∗ and a∗) and Metmyoglobin reducing activity of ground lamb patties were measured. Addition of lactate improved colour stability and Metmyoglobin reducing activity (p
Vitalii R. Vogel - One of the best experts on this subject based on the ideXlab platform.
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Enzyme-like effect of Metmyoglobin on the thermal cis-trans isomerization of stilbazolium betaine
Journal of Biological Inorganic Chemistry, 2000Co-Authors: Alexander V. Pastukhov, Vitalii R. Vogel, Alexander I. KotelnikovAbstract:A photochromic compound, stilbazolium betaine M, when associated with Metmyoglobin undergoes an accelerated thermal cis→trans isomerization. A study of the pH and ionic strength dependence of the isomerization reaction rate of the photochrome associated with Metmyoglobin was perfomed. A comparative investigation of the reaction carried out in the presence of three proteins, Metmyoglobin, apomyoglobin, and human albumin, indicates a specific influence of the heme pocket environment on the reaction. Possible mechanisms of the reaction acceleration are considered.
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Catalysis of the Back Thermal cis–trans Isomerization Reaction of Stilbazolium Betaine by Metmyoglobin
Journal of Fluorescence, 1999Co-Authors: Vitalii R. Vogel, Alexander V. Pastukhov, A. I. Kotel’nikovAbstract:The catalytic effect of Metmyoglobin on the back thermal cis → trans isomerization reaction of stilbazolium betaine M is reported. This reaction shows substantial acceleration in the presence of Metmyoglobin in comparison to the same reaction without the protein or in the presence of Metmyoglobin cyanide. It is suggested that the observed thermal reaction acceleration may arise from the coordination of the protonated stilbazolium betaine molecule to the sixth ligand position of the heme iron and subsequent chromophore deprotonation or from the low polarity of the heme pocket microenvironment.
Michael R Gunther - One of the best experts on this subject based on the ideXlab platform.
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Probing the free radicals formed in the Metmyoglobin–hydrogen peroxide reaction
Free Radical Biology and Medicine, 2004Co-Authors: Michael R GuntherAbstract:Abstract The reaction between Metmyoglobin and hydrogen peroxide results in the two-electron reduction of H2O2 by the protein, with concomitant formation of a ferryl-oxo heme and a protein-centered free radical. Sperm whale Metmyoglobin, which contains three tyrosine residues (Tyr-103, Tyr-146, and Tyr-151) and two tryptophan residues (Trp-7 and Trp-14), forms a tryptophanyl radical at residue 14 that reacts with O2 to form a peroxyl radical and also forms distinct tyrosyl radicals at Tyr-103 and Tyr-151. Horse Metmyoglobin, which lacks Tyr-151 of the sperm whale protein, forms an oxygen-reactive tryptophanyl radical and also a phenoxyl radical at Tyr-103. Human Metmyoglobin, in addition to the tyrosine and tryptophan radicals formed on horse Metmyoglobin, also forms a Cys-110-centered thiyl radical that can also form a peroxyl radical. The tryptophanyl radicals react both with molecular oxygen and with the spin trap 3,5-dibromo-4-nitrosobenzenesulfonic acid (DBNBS). The spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) traps the Tyr-103 radicals and the Cys-110 thiyl radical of human myoglobin, and 2-methyl-2-nitrosopropane (MNP) traps all of the tyrosyl radicals. When excess H2O2 is used, DBNBS traps only a tyrosyl radical on horse myoglobin, but the detection of peroxyl radicals and the loss of tryptophan fluorescence support tryptophan oxidation under those conditions. Kinetic analysis of the formation of the various free radicals suggests that tryptophanyl radical and tyrosyl radical formation are independent events, and that formation of the Cys-110 thiyl radical on human myoglobin occurs via oxidation of the thiol group by the Tyr-103 phenoxyl radical. Peptide mapping studies of the radical adducts and direct EPR studies at low temperature and room temperature support the conclusions of the EPR spin trapping studies.
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probing the free radicals formed in the Metmyoglobin hydrogen peroxide reaction
Free Radical Biology and Medicine, 2004Co-Authors: Michael R GuntherAbstract:Abstract The reaction between Metmyoglobin and hydrogen peroxide results in the two-electron reduction of H2O2 by the protein, with concomitant formation of a ferryl-oxo heme and a protein-centered free radical. Sperm whale Metmyoglobin, which contains three tyrosine residues (Tyr-103, Tyr-146, and Tyr-151) and two tryptophan residues (Trp-7 and Trp-14), forms a tryptophanyl radical at residue 14 that reacts with O2 to form a peroxyl radical and also forms distinct tyrosyl radicals at Tyr-103 and Tyr-151. Horse Metmyoglobin, which lacks Tyr-151 of the sperm whale protein, forms an oxygen-reactive tryptophanyl radical and also a phenoxyl radical at Tyr-103. Human Metmyoglobin, in addition to the tyrosine and tryptophan radicals formed on horse Metmyoglobin, also forms a Cys-110-centered thiyl radical that can also form a peroxyl radical. The tryptophanyl radicals react both with molecular oxygen and with the spin trap 3,5-dibromo-4-nitrosobenzenesulfonic acid (DBNBS). The spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) traps the Tyr-103 radicals and the Cys-110 thiyl radical of human myoglobin, and 2-methyl-2-nitrosopropane (MNP) traps all of the tyrosyl radicals. When excess H2O2 is used, DBNBS traps only a tyrosyl radical on horse myoglobin, but the detection of peroxyl radicals and the loss of tryptophan fluorescence support tryptophan oxidation under those conditions. Kinetic analysis of the formation of the various free radicals suggests that tryptophanyl radical and tyrosyl radical formation are independent events, and that formation of the Cys-110 thiyl radical on human myoglobin occurs via oxidation of the thiol group by the Tyr-103 phenoxyl radical. Peptide mapping studies of the radical adducts and direct EPR studies at low temperature and room temperature support the conclusions of the EPR spin trapping studies.
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tryptophan 14 is the preferred site of dbnbs spin trapping in the self peroxidation reaction of sperm whale Metmyoglobin with a single equivalent of hydrogen peroxide
Chemical Research in Toxicology, 2003Co-Authors: Michael R Gunther, Richard Tschirretguth, Olivier M Lardinois, Paul Ortiz R De MontellanoAbstract:The 3,5-dibromo-4-nitrosobenzenesulfonate (DBNBS)-Metmyoglobin adduct formed following the horse Metmyoglobin-H 2 O 2 reaction has been assigned to both a tyrosyl and a tryptophanyl residue radical. At low H 2 O 2 , hyperfine coupling to a 1 3 C atom in sperm whale Metmyoglobin labeled at the tryptophan residues with 1 3 C allowed the unequivocal assignment of the primary adduct to a tryptophanyl radical. Trapping at Trp-14 of sperm whale myoglobin was indicated by greatly decreased electron paramagnetic resonance (EPR) spectral intensity of the DBNBS adducts of the Trp-14-Phe recombinant proteins. Complex EPR spectra with partially resolved hyperfine splittings from several atoms were obtained by pronase treatment of the DBNBS/ .W14F Metmyoglobin adducts. The EPR spectra of authentic DBNBS/Tyr adducts were incubation time-dependent; the late time spectra resembled the spectra of pronase-treated DBNBS/W14F sperm whale myoglobin adducts, suggesting formation of an unstable tyrosyl radical adduct in the latter proteins. When the H 2 O 2 :Metmyoglobin ratio was increased to 5:1, the EPR spectrum after pronase treatment supported trapping of a tyrosyl radical, although similar decreases in tryptophan content were detected at H 2 O 2 :Metmyoglobin ratios of 1:1 and 5:1.