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Lucy Waskell - One of the best experts on this subject based on the ideXlab platform.
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the interaction of microsomal cytochrome p450 2b4 with its redox partners cytochrome p450 reductase and cytochrome b5
Archives of Biochemistry and Biophysics, 2011Co-Authors: Sang Choul Im, Lucy WaskellAbstract:Abstract Cytochrome P450 2B4 is a microsomal protein with a Multi-Step Reaction cycle similar to that observed in the majority of other cytochromes P450. The cytochrome P450 2B4-substrate complex is reduced from the ferric to the ferrous form by cytochrome P450 reductase. After binding oxygen, the oxyferrous protein accepts a second electron which is provided by either cytochrome P450 reductase or cytochrome b 5 . In both instances, product formation occurs. When the second electron is donated by cytochrome b 5 , catalysis (product formation) is ∼10- to 100-fold faster than in the presence of cytochrome P450 reductase. This allows less time for side product formation (hydrogen peroxide and superoxide) and improves by ∼15% the coupling of NADPH consumption to product formation. Cytochrome b 5 has also been shown to compete with cytochrome P450 reductase for a binding site on the proximal surface of cytochrome P450 2B4. These two different effects of cytochrome b 5 on cytochrome P450 2B4 reactivity can explain how cytochrome b 5 is able to stimulate, inhibit, or have no effect on cytochrome P450 2B4 activity. At low molar ratios ( b 5 to cytochrome P450 reductase, the more rapid catalysis results in enhanced substrate metabolism. In contrast, at high molar ratios (>1) of cytochrome b 5 to cytochrome P450 reductase, cytochrome b 5 inhibits activity by binding to the proximal surface of cytochrome P450 and preventing the reductase from reducing ferric cytochrome P450 to the ferrous protein, thereby aborting the catalytic Reaction cycle. When the stimulatory and inhibitory effects of cytochrome b 5 are equal, it will appear to have no effect on the enzymatic activity. It is hypothesized that cytochrome b 5 stimulates catalysis by causing a conformational change in the active site, which allows the active oxidizing oxyferryl species of cytochrome P450 to be formed more rapidly than in the presence of reductase.
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The interaction of microsomal cytochrome P450 2B4 with its redox partners, cytochrome P450 reductase and cytochrome b5
Archives of biochemistry and biophysics, 2010Co-Authors: Lucy WaskellAbstract:Cytochrome P450 2B4 is a microsomal protein with a Multi-Step Reaction cycle similar to that observed in the majority of other cytochromes P450. The cytochrome P450 2B4-substrate complex is reduced from the ferric to the ferrous form by cytochrome P450 reductase. After binding oxygen, the oxyferrous protein accepts a second electron which is provided by either cytochrome P450 reductase or cytochrome b(5). In both instances, product formation occurs. When the second electron is donated by cytochrome b(5), catalysis (product formation) is ∼10- to 100-fold faster than in the presence of cytochrome P450 reductase. This allows less time for side product formation (hydrogen peroxide and superoxide) and improves by ∼15% the coupling of NADPH consumption to product formation. Cytochrome b(5) has also been shown to compete with cytochrome P450 reductase for a binding site on the proximal surface of cytochrome P450 2B4. These two different effects of cytochrome b(5) on cytochrome P450 2B4 reactivity can explain how cytochrome b(5) is able to stimulate, inhibit, or have no effect on cytochrome P450 2B4 activity. At low molar ratios ( 1) of cytochrome b(5) to cytochrome P450 reductase, cytochrome b(5) inhibits activity by binding to the proximal surface of cytochrome P450 and preventing the reductase from reducing ferric cytochrome P450 to the ferrous protein, thereby aborting the catalytic Reaction cycle. When the stimulatory and inhibitory effects of cytochrome b(5) are equal, it will appear to have no effect on the enzymatic activity. It is hypothesized that cytochrome b(5) stimulates catalysis by causing a conformational change in the active site, which allows the active oxidizing oxyferryl species of cytochrome P450 to be formed more rapidly than in the presence of reductase.
Suchetha N Shetty - One of the best experts on this subject based on the ideXlab platform.
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synthesis and antimicrobial activities of some novel 1 2 4 triazolo 3 4 b 1 3 4 thiadiazoles and 1 2 4 triazolo 3 4 b 1 3 4 thiadiazines carrying thioalkyl and sulphonyl phenoxy moieties
European Journal of Medicinal Chemistry, 2007Co-Authors: T Karabasanagouda, Airody Vasudeva Adhikari, Suchetha N ShettyAbstract:Abstract Thirty one new 6-aryl-3-{(4-substituted phenoxy) methyl}-1,2,4-triazolo[3,4- b ]-1,3,4-thiadiazoles ( 6a – s ) and 6-aryl-3-{(4-substituted phenoxy methyl}-7 H -1,2,4-triazolo[3,4- b ]-1,3,4-thiadiazines ( 7a – l ) have been synthesized from 4-thioalkyl phenols ( 1a – b ) through a Multi-Step Reaction sequence. Compounds 1a – b reacted with ethyl chloroacetate in presence of acetone and potassium carbonate to give ethyl [4-(thioalkyl) phenoxy] acetates ( 2a – b ). Further, 2a was oxidized to [4-(methyl sulphonyl) phenoxy] acetate ( 2c ) using hydrogen peroxide in acetic acid. Reactions of ( 2a – c ) with hydrazine hydrate in alcoholic medium furnished 2-[4-thiosubstituted phenoxy] acetohydrazides ( 3a – b ) and 2-[4-methyl sulphonyl phenoxy] acetohydrazide ( 3c ) which on treatment with carbon disulphide and methanolic potassium hydroxide yielded corresponding potassium dithiocarbazates ( 4a – c ). They were then converted to 4-amino-5-{(4-thioalkyl phenoxy) methyl}-4 H -1,2,4-triazole-3-thiols ( 5a – b ) and 4-amino-5-{(4-methyl sulphonyl phenoxy) methyl}-4 H -1,2,4-triazole-3-thiol ( 5c ) by refluxing them with aqueous hydrazine hydrate. The title compounds 6a – s were prepared by condensing 5a – c with various aromatic carboxylic acids in presence of phosphorus oxychloride. The intermediates 5a – c , on condensation with various substituted phenacyl bromides afforded a series of title compounds ( 7a – l ). The structures of new compounds 2a – 7l were established on the basis of their elemental analysis, IR, 1 H NMR, 13 C NMR and mass spectral data. All the title compounds were subjected to in vitro antibacterial testing against four pathogenic strains and antifungal screening against three fungi. Preliminary results indicate that some of them exhibited promising activities and they deserve more consideration as potential antimicrobials.
Wun Jern Ng - One of the best experts on this subject based on the ideXlab platform.
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microbial stress mediated intercellular nanotubes in an anaerobic microbial consortium digesting cellulose
Scientific Reports, 2017Co-Authors: Martina John, Antoine P Trzcinski, Yan Zhou, Wun Jern NgAbstract:The anaerobic digestion process is a multi - step Reaction dependent on concerted activities such as exchange of metabolites among physiologically different microbial communities. This study investigated the impact of iron oxide nanoparticles on the anaerobic sludge microbiota. It was shown there were three distinct microbial phases following addition of the nanoparticles: microbial stress and cell death of approximately one log order of magnitude, followed by microbial rewiring, and recovery. Furthermore, it was noted that cellular stress led to the establishment of intercellular nanotubes within the microbial biomass. Intercellular nanotube - mediated communication among genetically engineered microorganisms and ad hoc assembled co - cultures have been previously reported. This study presents evidence of intercellular nanotube formation within an environmental sample – i.e., anaerobic sludge microbiota subjected to stress. Our observations suggested a mode of microbial communication in the anaerobic digestion process not previously explored and which may have implications on bioreactor design and microbial functions.
Jamal Naser - One of the best experts on this subject based on the ideXlab platform.
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Computational fluid dynamic modelling of a 550 MW tangentially-fired furnace under different operating conditions
Procedia Engineering, 2013Co-Authors: Audai Hussein Al-abbas, Jamal NaserAbstract:In the present paper, a computational fluid dynamics (CFD) modelling study was performed for the combustion of the brown coal in a large-scale tangentially-fired furnace (550 MW) under different operating conditions. The AVL Fire CFD code has been used to model the furnace. The mathematical models of coal combustion with the appropriate kinetic parameters were written and added to the code as user defined functions. It consists of pulverised coal (PC) devolatilization, char burnout, heat and mass transfer, and nitric oxide formation. The simulation of the PC combustion was carried out using Multi-Step Reaction chemistry schemes. The level of confidence of this numerical model was based on the previous validations of the lignite combustion in a lab-scale furnace, as well as the validation parameters of the present furnace at the standard existing conditions in terms of temperature values and species concentrations. Performance of the boiler under different operating conditions was investigated, from which the effects of air and coal mass flow rates were considered at full load with different operating schemes of coal mills (out-of-service operations). The validated model was used to perform the following investigation parameters: furnace gas temperatures, species concentrations (CO and CO2), and velocity distributions. This study provides good information to optimize the operations of the utility tangentially-fired boiler with less emissions production.
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Numerical simulation of brown coal combustion in a 550 MW tangentially-fired furnace under different operating conditions
Fuel, 2013Co-Authors: Audai Hussein Al-abbas, Jamal Naser, Emad Kamil HusseinAbstract:In the present paper, a computational fluid dynamics (CFD) modeling study was performed for the combustion of the brown coal in a large-scale tangentially-fired furnace (550 MW) under different operating conditions. The AVL Fire CFD code has been used to model the combustion processes. The mathematical models of coal combustion with the appropriate kinetic parameters were written and incorporated to the code as user defined functions. These models consist of pulverised coal (PC) devolatilization, char burnout, and heat and mass transfer. The simulation of the PC combustion was carried out using Multi-Step Reaction chemistry mechanisms. The level of confidence of this numerical model was based on the previous validations of the lignite combustion in a lab-scale furnace, as well as the validation parameters of the present furnace at the standard existing conditions in terms of temperature values and species concentrations. Performance of the boiler under ten different operating conditions was investigated. The strategy of operation schemes for the first six combustion scenarios were based on the change of the out-of-service (turned off) burners under full load operation, while the rest cases were carried out at 20% lower and 20% higher loads than the standard operating conditions. The validated model was used to perform the following investigation parameters: furnace gas temperatures, species concentrations (O2, CO and CO2), velocity distributions, and char consumption. The predictions demonstrated that there are good temperature distributions in the furnace when the turned off burners are set in the opposite direction under full load operation. For higher aerodynamic effect, the numerical results showed improvements on the combustion characteristics in terms of species concentrations and char burnout rates in comparison with the standard operating case. The findings of this study provide good information to optimize the operations of the utility tangentially coal-fired boiler with less emission
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numerical study of one air fired and two oxy fuel combustion cases of propane in a 100 kw furnace
Energy & Fuels, 2012Co-Authors: Audai Hussein Alabbas, Jamal NaserAbstract:A computational fluid dynamics (CFD) modeling study has been carried out. The study involved gaseous fuel combustion with associated chemical Reactions, radiative heat transfer, and turbulence. The three different combustion environments that were adopted experimentally in a 100 kW drop-tube firing unit were examined. One air-fired and two oxy-fuel-fired cases [21 vol % O2 for one combustion case (OF21) and 27 vol % O2 for the other combustion case (OF27)] were investigated. A swirl injection system was used to achieve the flame stability of the turbulent non-premixed combustible gases. A modified eddy breakup (EBU) model was used with appropriate empirical coefficients for propane combustion Reactions. The irreversible single-step and reversible Multi-Step Reaction mechanisms were considered. The overall agreement of the CFD results with the available measured data was reasonable. The data compared were the temperature distributions and the species concentrations (CO2, CO, and O2) at the most intensive c...
Sang Choul Im - One of the best experts on this subject based on the ideXlab platform.
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the interaction of microsomal cytochrome p450 2b4 with its redox partners cytochrome p450 reductase and cytochrome b5
Archives of Biochemistry and Biophysics, 2011Co-Authors: Sang Choul Im, Lucy WaskellAbstract:Abstract Cytochrome P450 2B4 is a microsomal protein with a Multi-Step Reaction cycle similar to that observed in the majority of other cytochromes P450. The cytochrome P450 2B4-substrate complex is reduced from the ferric to the ferrous form by cytochrome P450 reductase. After binding oxygen, the oxyferrous protein accepts a second electron which is provided by either cytochrome P450 reductase or cytochrome b 5 . In both instances, product formation occurs. When the second electron is donated by cytochrome b 5 , catalysis (product formation) is ∼10- to 100-fold faster than in the presence of cytochrome P450 reductase. This allows less time for side product formation (hydrogen peroxide and superoxide) and improves by ∼15% the coupling of NADPH consumption to product formation. Cytochrome b 5 has also been shown to compete with cytochrome P450 reductase for a binding site on the proximal surface of cytochrome P450 2B4. These two different effects of cytochrome b 5 on cytochrome P450 2B4 reactivity can explain how cytochrome b 5 is able to stimulate, inhibit, or have no effect on cytochrome P450 2B4 activity. At low molar ratios ( b 5 to cytochrome P450 reductase, the more rapid catalysis results in enhanced substrate metabolism. In contrast, at high molar ratios (>1) of cytochrome b 5 to cytochrome P450 reductase, cytochrome b 5 inhibits activity by binding to the proximal surface of cytochrome P450 and preventing the reductase from reducing ferric cytochrome P450 to the ferrous protein, thereby aborting the catalytic Reaction cycle. When the stimulatory and inhibitory effects of cytochrome b 5 are equal, it will appear to have no effect on the enzymatic activity. It is hypothesized that cytochrome b 5 stimulates catalysis by causing a conformational change in the active site, which allows the active oxidizing oxyferryl species of cytochrome P450 to be formed more rapidly than in the presence of reductase.