The Experts below are selected from a list of 34116 Experts worldwide ranked by ideXlab platform
Luke I Szweda - One of the best experts on this subject based on the ideXlab platform.
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selective inactivation of alpha ketoglutarate dehydrogenase and pyruvate dehydrogenase reaction of lipoic acid with 4 hydroxy 2 nonenal
Biochemistry, 1998Co-Authors: Kenneth M Humphries, Luke I SzwedaAbstract:Previous research has established that 4-hydroxy-2-nonenal (HNE), a highly Toxic Product of lipid peroxidation, is a potent inhibitor of mitochondrial respiration. HNE exerts its effects on respiration by inhibiting α-ketoglutarate dehydrogenase (KGDH). Because of the central role of KGDH in metabolism and emerging evidence that free radicals contribute to mitochondrial dysfunction associated with numerous diseases, it is of great interest to further characterize the mechanism of inhibition. In the present study, treatment of rat heart mitochondria with HNE resulted in the selective inhibition of KGDH and pyruvate dehydrogenase (PDH), while other NADH-linked dehydrogenases and electron chain complexes were unaffected. KGDH and PDH are structurally and catalytically similar multienzyme complexes, suggesting a common mode of inhibition. To determine the mechanism of inhibition, the effects of HNE on purified KGDH and PDH were examined. These studies revealed that inactivation by HNE was greatly enhanced in ...
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selective inactivation of alpha ketoglutarate dehydrogenase and pyruvate dehydrogenase reaction of lipoic acid with 4 hydroxy 2 nonenal
Biochemistry, 1998Co-Authors: Kenneth M Humphries, Luke I SzwedaAbstract:Previous research has established that 4-hydroxy-2-nonenal (HNE), a highly Toxic Product of lipid peroxidation, is a potent inhibitor of mitochondrial respiration. HNE exerts its effects on respiration by inhibiting alpha-ketoglutarate dehydrogenase (KGDH). Because of the central role of KGDH in metabolism and emerging evidence that free radicals contribute to mitochondrial dysfunction associated with numerous diseases, it is of great interest to further characterize the mechanism of inhibition. In the present study, treatment of rat heart mitochondria with HNE resulted in the selective inhibition of KGDH and pyruvate dehydrogenase (PDH), while other NADH-linked dehydrogenases and electron chain complexes were unaffected. KGDH and PDH are structurally and catalytically similar multienzyme complexes, suggesting a common mode of inhibition. To determine the mechanism of inhibition, the effects of HNE on purified KGDH and PDH were examined. These studies revealed that inactivation by HNE was greatly enhanced in the presence of substrates that reduce the sulfur atoms of lipoic acid covalently bound to the E2 subunits of KGDH and PDH. In addition, loss of enzyme activity induced by HNE correlated closely with a decrease in the availability of lipoic acid sulfhydryl groups. Use of anti-lipoic acid antibodies indicated that HNE modified lipoic acid in both purified enzyme preparations and mitochondria and that this modification was dependent upon the presence of substrates. These results therefore identify a potential mechanism whereby free radical Production and subsequent lipid peroxidation lead to specific modification of KGDH and PDH and inhibition of NADH-linked mitochondrial respiration.
Anna A. Stec - One of the best experts on this subject based on the ideXlab platform.
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Quantification of Toxic hazard from fires in buildings
Journal of Building Engineering, 2016Co-Authors: T. Richard Hull, Dieter Brein, Anna A. StecAbstract:Abstract Fire safe design requires a builder, architect or fire safety engineer to ensure that the available safe escape time (ASET) exceeds the required safe escape time (RSET), for which an estimate of Toxic hazard from smoke is required. In Europe, the burning behaviour of construction Products must be tested and labelled according to their Euroclass, based on their fire performance in a range of tests. Each Euroclass can be used to indicate a mass loss range. The yields of Toxic Products may be determined for each material as a function of fire condition. Reliable data has been widely reported from the steady state tube furnace (ISO TS 19700) and the fire propagation apparatus (ISO 12136) for both well-ventilated and under-ventilated flaming. By combining the Toxic Product yields, most easily expressed as an LC 50 , with the mass loss range, a methodology is proposed for quantifying the volume of Toxic effluent produced by burning construction materials within an enclosure. This allows a maximum safe loading of construction materials to be quantified for a given volume of enclosure. This is intended to ensure that estimates of Toxic hazard are undertaken as part of any fire hazard assessment, not to replace more rigorous engineering analyses. It will allow architects and builders to ensure that their materials’ selection does not compromise fire safety.
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effects of the material and fire conditions on Toxic Product yields
Fire Toxicity, 2010Co-Authors: D.a. Purser, Anna A. Stec, T.r. HullAbstract:Fire gases contain a mixture of fully oxidised Products, such as carbon dioxide, partially oxidised Products, such as carbon monoxide or aldehydes, fuel or fuel degradation Products, including aliphatic or aromatic hydrocarbons, and other stable gas molecules, such as nitrogen and hydrogen halides. The yields of most of the species depend on the material composition, the decomposition conditions (non-flaming or flaming) and, for flaming, the ventilation conditions. This chapter examines the effects of the main parameters determining Product yields, illustrated with data for six common polymeric materials obtained using the ISO 19700 tube furnace, which is found to provide an excellent method for exploring the relationship between combustion conditions and Product yields.
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Comparison of Toxic Product yields from bench-scale to ISO room
Fire Safety Journal, 2009Co-Authors: Anna A. Stec, T.r. Hull, J. A. Purser, D.a. PurserAbstract:Abstract Toxic Products are the main cause of fire injuries and deaths, but available methods for measuring or calculating Toxic Product yields have severe limitations. Full-scale or large-scale experimental re-creations of fire scenarios are sometimes used for the assessment of Toxic hazard, but such tests are expensive, while small-scale or even larger-scale tests often provide poor simulations of full-scale conditions. From a testing and engineering calculation perspective there is a need for test methods to provide data-enabling calculations of Toxic Product yields in defined full-scale scenarios. Full-scale and large-scale tests have demonstrated that Toxic Product yields are highly dependent upon the combustion conditions. Fire stages and types can be characterised either in terms of CO 2 /CO ratio, or preferably in terms of equivalence ratio, which provide reasonably good predictive metrics for Product yields. The steady-state tube furnace (ISO TS 19700) allows individual fire stages to be replicated and shows a good general agreement with Product yield data (measured for CO 2 , CO, HCN, NO x , total hydrocarbons and smoke particulates) obtained from large-scale ISO room tests for the five materials considered here and expressed as functions of equivalence ratio and CO 2 /CO ratio. The closest direct agreement between the large- and small-scale data were obtained for pool fires involving PP and nylon 6.6 Product yield. For materials burned as wall linings, with varying decomposition conditions at different room locations, and/or when a propane flame is also present, direct comparison with tube-furnace data is more problematic. Nevertheless MDF, MDF-FR and PS show reasonable agreement for CO, CO 2 , HCN and hydrocarbon yields between the scales. Smoke yields tended to be more variable and may be influenced by the presence of different areas of flaming and non-flaming decomposition.
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characterisation of the steady state tube furnace iso ts 19700 for fire Toxicity assessment
Polymer Degradation and Stability, 2008Co-Authors: Anna A. Stec, Richard T Hull, K LebekAbstract:Abstract The steady state tube furnace (Purser furnace, ISO TS 19700) has been developed specifically to replicate the generation of Toxic Products from real fires under different fire conditions on a bench-scale. Steady state burning is achieved by driving the sample into a furnace of increasing heat flux at a fixed rate and recording the Product yields over a steady state period in the middle of the run. The furnace, sample, and effluent dilution chamber temperature profiles are presented to characterise the conditions in the apparatus. The distribution of smoke in the mixing chamber has been investigated to demonstrate the efficiency of mixing in the effluent dilution chamber. The heat flux applied to the sample at various points through the furnace has been measured, showing that conditions vary from those typical of pre-flaming to fully developed fires. An initial investigation of the repeatability and interlaboratory reproducibility has been undertaken, showing acceptable low levels of uncertainty in the Toxic Product yields.
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A Comparison of Toxic Product Yields Obtained From Five Laboratories Using the Steady State Tube Furnace (ISO TS 19700)
Fire Safety Science, 2008Co-Authors: Anna A. Stec, T.r. Hull, J. A. Purser, Per Blomqvist, K LebekAbstract:The steady state tube furnace has been developed from BS 7990 into the first internationally recognized standard for assessment of fire gas Toxicity, ISO TS 19700. The apparatus has been shown to reliably replicate different fire stages, and is capable of generating Toxic Product yields as a function of the equivalence ratio φ. Work is reported from 5 laboratories currently using the steady state tube furnace where it has been used to assess the Toxic Product yields from a range of generic polymer materials, as a function of equivalence ratio. For the polymers tested, (LDPE, PP, PVC, Nylon, and PS) a high degree of reproducibility is observed across the range of ventilation conditions. In particular, the carbon monoxide yield, which is most susceptible to fire conditions shows consistent behaviour, which is independent of a particular laboratory.
K Lebek - One of the best experts on this subject based on the ideXlab platform.
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characterisation of the steady state tube furnace iso ts 19700 for fire Toxicity assessment
Polymer Degradation and Stability, 2008Co-Authors: Anna A. Stec, Richard T Hull, K LebekAbstract:Abstract The steady state tube furnace (Purser furnace, ISO TS 19700) has been developed specifically to replicate the generation of Toxic Products from real fires under different fire conditions on a bench-scale. Steady state burning is achieved by driving the sample into a furnace of increasing heat flux at a fixed rate and recording the Product yields over a steady state period in the middle of the run. The furnace, sample, and effluent dilution chamber temperature profiles are presented to characterise the conditions in the apparatus. The distribution of smoke in the mixing chamber has been investigated to demonstrate the efficiency of mixing in the effluent dilution chamber. The heat flux applied to the sample at various points through the furnace has been measured, showing that conditions vary from those typical of pre-flaming to fully developed fires. An initial investigation of the repeatability and interlaboratory reproducibility has been undertaken, showing acceptable low levels of uncertainty in the Toxic Product yields.
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comparison of Toxic Product yields of burning cables in bench and large scale experiments
Fire Safety Journal, 2008Co-Authors: Richard T Hull, K Lebek, Maddalena Pezzani, Silvio MessaAbstract:Abstract Toxic Product yields from five commercial cables obtained from a steady state tube furnace (SSTF) method (IEC 60695-7-50, Purser furnace) are compared with results from a large-scale test, which uses the physical fire model in the proposed prEN50399-2-2 test, with the addition of effluent gas analysis, using Fourier transform infrared (FTIR), and for further comparison, a static tube furnace method (NF X 70-100). This work represents one of the first attempts to establish a relationship between bench- and large-scale Toxic Product yields for burning cables. This is difficult because the cables have been formulated for low flammability, and therefore do not burn consistently. The tube furnace burns the cable completely, whereas the large-scale test effluent is the result of a combination of flame spread and Toxic Product yields, both of which are fire scenario dependant. There is significant differentiation between cable types based on composition, and arising because only a portion of the cables burn in the large-scale test, accompanied by possible decomposition of hydrate sheaths. The fire stage of the large-scale test appears to have been replicated in an appropriate manner, given the correspondence of the CO 2 /CO ratios. The yields of CO 2 , CO, HCl and smoke show reasonable agreement, given the differences in the extent of burning, and the accuracy of the mass-loss data available for the large-scale test. The yields and extent of burning have been combined to demonstrate the estimation of Toxic hazard for a particular fire scenario based around the large-scale test, which shows only marginal sensitivity to the differences in Toxic Product yield between the SSTF and the large-scale test.
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A Comparison of Toxic Product Yields Obtained From Five Laboratories Using the Steady State Tube Furnace (ISO TS 19700)
Fire Safety Science, 2008Co-Authors: Anna A. Stec, T.r. Hull, J. A. Purser, Per Blomqvist, K LebekAbstract:The steady state tube furnace has been developed from BS 7990 into the first internationally recognized standard for assessment of fire gas Toxicity, ISO TS 19700. The apparatus has been shown to reliably replicate different fire stages, and is capable of generating Toxic Product yields as a function of the equivalence ratio φ. Work is reported from 5 laboratories currently using the steady state tube furnace where it has been used to assess the Toxic Product yields from a range of generic polymer materials, as a function of equivalence ratio. For the polymers tested, (LDPE, PP, PVC, Nylon, and PS) a high degree of reproducibility is observed across the range of ventilation conditions. In particular, the carbon monoxide yield, which is most susceptible to fire conditions shows consistent behaviour, which is independent of a particular laboratory.
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the effect of temperature and ventilation condition on the Toxic Product yields from burning polymers
Fire and Materials, 2008Co-Authors: Anna A. Stec, T.r. Hull, J. A. Purser, K Lebek, D.a. PurserAbstract:A major cause of death or permanent injury in fires is inhalation of Toxic gases. Moreover, every fire is unique, and the range of Products, highly dependant on fire conditions, produces a wide variety of Toxic and irritant species responsible for the most fire fatalities. Therefore, to fully understand each contribution to the Toxicity it is necessary to quantify the decomposition Products of the material under the test. Fires can be divided into a number of stages from smouldering combustion to early wellventilated flaming, through to fully developed under-ventilated flaming. These stages can be replicated by certain bench-scale physical fire models using different fuel-to-oxygen ratios, controlled by the primary air flow, and expressed in terms of the equivalence ratio (the actual fuel/air ratio divided by the stoichiometric fuel/air ratio). This work presents combustion Product yields generated using a small-scale fire model. The Purser Furnace apparatus (BS7990 and ISO TS 19700) enables different fire stages to be created. Identification and quantification of combustion gases and particularly their Toxic components from different fire scenarios was undertaken by continuous Fourier Transform Infrared Spectroscopy. The relationship between type of the fire particularly the temperature and ventilation conditions, and the Toxic Product yields for four bulk polymers, LDPE, PS, Nylon 6.6 and PVC are reported. For all the polymers tested, except PVC, there is a dramatic increase in the yield of Products of incomplete combustion (CO and hydrocarbons) with increase in equivalence ratio, as might be expected. For PVC there is a consistently high level of Products of incomplete combustion arising both from flame inhibition by HCl, and oxygen depletion. There is a low sensitivity to furnace temperature over the range 650-850°C, except that at 650°C PS shows an unexpectedly high yield of CO under well-ventilated conditions and PVC shows a slightly higher hydrocarbon yield. This demonstrates the dependence of Toxic Product yields on the equivalence ratio, and the lack of dependence on furnace temperature, within this range.
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correlation of Toxic Product yields from tube furnace tests and large scale fires
Fire Safety Science, 2005Co-Authors: T.r. Hull, K Lebek, Keith T PaulAbstract:Toxic Product yields obtained from a steady state tube furnace method (the Purser furnace, IEC 60695-7-50) are compared with results reported for a static tube furnace (suitable for IEC 60754-2) and a large scale test (the European Horizontal Reference Scenario Test for cables, enclosed in an ISO 9705 room). Data for burning polypropylene as a function of equivalence ratio shows excellent correlation between small and large scale. Results from four commercial cable types are also reported, and compared with static tube furnace data, and the horizontal reference scenario now accepted for European cable flammability assessment. These show varying degrees of correlation, as may be expected given the complex nature of cable construction and burning and the large differences between the fire types involved.
Kenneth M Humphries - One of the best experts on this subject based on the ideXlab platform.
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selective inactivation of alpha ketoglutarate dehydrogenase and pyruvate dehydrogenase reaction of lipoic acid with 4 hydroxy 2 nonenal
Biochemistry, 1998Co-Authors: Kenneth M Humphries, Luke I SzwedaAbstract:Previous research has established that 4-hydroxy-2-nonenal (HNE), a highly Toxic Product of lipid peroxidation, is a potent inhibitor of mitochondrial respiration. HNE exerts its effects on respiration by inhibiting α-ketoglutarate dehydrogenase (KGDH). Because of the central role of KGDH in metabolism and emerging evidence that free radicals contribute to mitochondrial dysfunction associated with numerous diseases, it is of great interest to further characterize the mechanism of inhibition. In the present study, treatment of rat heart mitochondria with HNE resulted in the selective inhibition of KGDH and pyruvate dehydrogenase (PDH), while other NADH-linked dehydrogenases and electron chain complexes were unaffected. KGDH and PDH are structurally and catalytically similar multienzyme complexes, suggesting a common mode of inhibition. To determine the mechanism of inhibition, the effects of HNE on purified KGDH and PDH were examined. These studies revealed that inactivation by HNE was greatly enhanced in ...
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selective inactivation of alpha ketoglutarate dehydrogenase and pyruvate dehydrogenase reaction of lipoic acid with 4 hydroxy 2 nonenal
Biochemistry, 1998Co-Authors: Kenneth M Humphries, Luke I SzwedaAbstract:Previous research has established that 4-hydroxy-2-nonenal (HNE), a highly Toxic Product of lipid peroxidation, is a potent inhibitor of mitochondrial respiration. HNE exerts its effects on respiration by inhibiting alpha-ketoglutarate dehydrogenase (KGDH). Because of the central role of KGDH in metabolism and emerging evidence that free radicals contribute to mitochondrial dysfunction associated with numerous diseases, it is of great interest to further characterize the mechanism of inhibition. In the present study, treatment of rat heart mitochondria with HNE resulted in the selective inhibition of KGDH and pyruvate dehydrogenase (PDH), while other NADH-linked dehydrogenases and electron chain complexes were unaffected. KGDH and PDH are structurally and catalytically similar multienzyme complexes, suggesting a common mode of inhibition. To determine the mechanism of inhibition, the effects of HNE on purified KGDH and PDH were examined. These studies revealed that inactivation by HNE was greatly enhanced in the presence of substrates that reduce the sulfur atoms of lipoic acid covalently bound to the E2 subunits of KGDH and PDH. In addition, loss of enzyme activity induced by HNE correlated closely with a decrease in the availability of lipoic acid sulfhydryl groups. Use of anti-lipoic acid antibodies indicated that HNE modified lipoic acid in both purified enzyme preparations and mitochondria and that this modification was dependent upon the presence of substrates. These results therefore identify a potential mechanism whereby free radical Production and subsequent lipid peroxidation lead to specific modification of KGDH and PDH and inhibition of NADH-linked mitochondrial respiration.
Dayanand Kalyani - One of the best experts on this subject based on the ideXlab platform.
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effectual decolorization and detoxification of triphenylmethane dye malachite green mg by pseudomonas aeruginosa ncim 2074 and its enzyme system
Clean Technologies and Environmental Policy, 2012Co-Authors: Dayanand Kalyani, Amar A Telke, Shripad N Surwase, Shekhar B Jadhav, Jungkul Lee, Jyoti P JadhavAbstract:Malachite green (MG) a complex and resonance-stabilized triphenylmethane (TPM) textile dye, resistant to transformation, was decolorized using Pseudomonas aeruginosa NCIM 2074. The bacteria decolorized MG (50 mg l−1) completely within 5 h into simple metabolic intermediates in aerobic condition at pH 7 and temperature 35 ± 3°C with 53.23% of the COD reduction. Induction in the activities of MG reductase, laccase, and aminopyrine N-demethylase were observed during MG decolorization suggesting these enzymes were involved in the decolorization process. The Products after decolorization were examined by UV–Vis, IR spectroscopy, TLC, and HPLC. MG was enzymatically reduced to leucomalachite green (LMG), and further sequential enzymatic reaction converted LMG into N-demethylated and N-oxidized metabolites, including primary and secondary arylamines. The final Product formed in this pathway was benzophenone characterized using GC-mass spectroscopy. The cytoToxicity and phytoToxicity study revealed the transformation of MG into non-Toxic Product by P. aeruginosa NCIM 2074.
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ecofriendly biodegradation and detoxification of reactive red 2 textile dye by newly isolated pseudomonas sp suk1
Journal of Hazardous Materials, 2009Co-Authors: Dayanand Kalyani, Ama A Telke, Rhishikesh S Dhanve, Jyoti P JadhavAbstract:Abstract The aim of this work is to evaluate textile dyes degradation by novel bacterial strain isolated from the waste disposal sites of local textile industries. Detailed taxonomic studies identified the organisms as Pseudomonas species and designated as strain Pseudomonas sp. SUK1. The isolate was able to decolorize sulfonated azo dye (Reactive Red 2) in a wide range (up to 5 g l −1 ), at temperature 30 °C, and pH range 6.2–7.5 in static condition. This isolate also showed decolorization of the media containing a mixture of dyes. Measurements of COD were done at regular intervals to have an idea of mineralization, showing 52% reduction in the COD within 24 h. Induction in the activity of lignin peroxidase and azoreductase was observed during decolorization of Reactive Red 2 in the batch culture, which represented their role in degradation. The biodegradation was monitored by UV–vis, IR spectroscopy, HPLC. The final Product, 2-naphthol was characterized by GC-mass spectroscopy. The phytoToxicity study revealed the degradation of Reactive Red 2 into non-Toxic Product by Pseudomonas sp. SUK1.
