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Robert Verger - One of the best experts on this subject based on the ideXlab platform.
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hydrolysis of mixed Monomolecular Films of tricaprylin dilauroylphosphatidylcholine by lipase and phospholipase a2
Colloids and Surfaces B: Biointerfaces, 2011Co-Authors: K Mircheva, I Panaiotov, Tz Ivanova, Robert VergerAbstract:Abstract The purpose of this article was to describe the kinetics of the enzymatic action of one or more enzymes on mixture of substrates organized in 2D structures in order to mimic some situations existing in biological or industrial systems. Hydrolysis of the mixed Monomolecular Films of tricaprylin/dilauroylphosphatidylcholine (TC8/DiC12PC) by Thermomyces lanuginosus lipase (TLL) and phospholipase A 2 (PLA 2 ) was studied by measuring the decrease of the surface area and change of the surface potential at barostatic conditions. The decrease of the surface area detects the transition of the substrate into reaction products and their solubilization while the change of the surface potential detects the contribution of dipole moment of the molecules remaining at the interface during the hydrolysis. The kinetic models, describing the interfacial hydrolysis allowed us to estimate the values of the global kinetic constants for TC8 and DiC12PC hydrolysis, respectively. The role of interaction between all participants of the catalytic act in that complex catalytic system is shown. The catalytic activity of TLL and PLA 2 is affected by the molecular environment in TC8/DiC12PC mixed monolayers.
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Hydrolysis of mixed Monomolecular Films of tricaprylin/dilauroylphosphatidylcholine by lipase and phospholipase A2
Colloids and Surfaces B: Biointerfaces, 2011Co-Authors: K Mircheva, I Panaiotov, Tz Ivanova, Robert VergerAbstract:Abstract The purpose of this article was to describe the kinetics of the enzymatic action of one or more enzymes on mixture of substrates organized in 2D structures in order to mimic some situations existing in biological or industrial systems. Hydrolysis of the mixed Monomolecular Films of tricaprylin/dilauroylphosphatidylcholine (TC8/DiC12PC) by Thermomyces lanuginosus lipase (TLL) and phospholipase A 2 (PLA 2 ) was studied by measuring the decrease of the surface area and change of the surface potential at barostatic conditions. The decrease of the surface area detects the transition of the substrate into reaction products and their solubilization while the change of the surface potential detects the contribution of dipole moment of the molecules remaining at the interface during the hydrolysis. The kinetic models, describing the interfacial hydrolysis allowed us to estimate the values of the global kinetic constants for TC8 and DiC12PC hydrolysis, respectively. The role of interaction between all participants of the catalytic act in that complex catalytic system is shown. The catalytic activity of TLL and PLA 2 is affected by the molecular environment in TC8/DiC12PC mixed monolayers.
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action of humicola lanuginosa lipase on mixed Monomolecular Films of tricaprylin and polyethylene glycol stearate
Colloids and Surfaces B: Biointerfaces, 2008Co-Authors: Tz Ivanova, K Mircheva, G Dobreva, I Panaiotov, J E Proust, Robert VergerAbstract:Abstract The hydrolysis catalyzed by Humicola lanuginosa lipase (HLL) of pure tricaprylin (TC) or stearate of polyethylene glycol 1500 (PEG-St) as well as their mixtures spread as Monomolecular Films were studied. The catalytic transformation of the two substrates TC or PEG-St into their respective reaction products was detected by measuring simultaneously the decrease in the film area and the surface potential using the “zero order” trough at constant surface pressure. A kinetic model describing the enzymatic hydrolysis was developed. The surface concentrations of the two substrates and their respective reaction products as well as the values of the global kinetic constants of hydrolysis were determined. The experimentally obtained global kinetic constants of the catalytic action of HLL against TC and PEG-St present in mixed monolayers of TC/PEG-St are approximately the same as in the case of pure monolayers. These obtained results give some indications that the activity of enzyme is not significantly affected by the different molecular environments in the mixed monolayers.
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surface fluorescence resonance energy transfer studies on interfacial adsorption of thermomyces humicola lanuginosa lipase using Monomolecular Films of cis parinaric acid
Biopolymers, 2002Co-Authors: S Yapoudjian, Margarita G Ivanova, Isabelle Douchet, A Zenatti, M Sentis, W Marine, Allan Svendsen, Robert VergerAbstract:The fluorescence resonance energy transfer (FRET) technique was adapted to study the process whereby lipase is adsorbed to Monomolecular lipid Films spread at the air–water interface. When cis-parinaric acid (cis-PnA) was spread over an aqueous subphase before the injection of sodium taurodeoxycholate (NaTDC) and Thermomyces lanuginosa lipase (TLL), no FRET was observed. Under these conditions, no adsorption of TLL was detected using an ELISA. In contrast, FRET occurred when cis-PnA was spread over an aqueous subphase containing NaTDC and TLL. The FRET signals observed were attributed to the interactions between the adsorbed TLL and the cis-PnA Monomolecular Films. Comparisons between the fluorescence emission spectra corresponding to the bulk phase and the aspirated film, in the presence and absence of TLL, showed that cis-PnA was undetectable in the bulk phase. We concluded that the FRET originated from the interface and not from the bulk phase. Using surface FRET, we estimated that the surface excess of the catalytically inactive mutant, TLL(S146A), was 1.6 higher than that present in the wild-type TLL. This finding is in agreement with independent measurements of the surface excess of TLL and TLL(S146A) on Monomolecular Films of cis-PnA. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 65: 121–128, 2002
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hydrolysis of 1 2 rac dicaprin Monomolecular Films by humicola lanuginosa as reflected in the surface potential
Colloids and Surfaces B: Biointerfaces, 2000Co-Authors: M Ivanova, Robert Verger, Allan Svendsen, I PanaiotovAbstract:Abstract The kinetics of the hydrolysis of 1,2-rac-dicaprin Monomolecular Films were measured from the decrease in the film area and the simultaneous changes in the surface potential at a constant surface pressure. A new kinetic model, based on the rate of product desorption is described. The surface potential data were interpreted in the light of the hydrolytic products accumulated at the interface. The surface concentration of the lipolytic products transiently present at the interface and the characteristic solubilization time of the lipolytic products were estimated. At surface pressures of more than 10 mN m−1, the amount of lipolytic products accumulated at the interface was found to be negligible in line with the simple kinetic model first developed in 1973 by R. Verger et al. (R. Verger, M.C.E. Mieras, G.H. de Haas, J. Biol. Chem., 248 (1973) 4023).
K Mircheva - One of the best experts on this subject based on the ideXlab platform.
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hydrolysis of mixed Monomolecular Films of tricaprylin dilauroylphosphatidylcholine by lipase and phospholipase a2
Colloids and Surfaces B: Biointerfaces, 2011Co-Authors: K Mircheva, I Panaiotov, Tz Ivanova, Robert VergerAbstract:Abstract The purpose of this article was to describe the kinetics of the enzymatic action of one or more enzymes on mixture of substrates organized in 2D structures in order to mimic some situations existing in biological or industrial systems. Hydrolysis of the mixed Monomolecular Films of tricaprylin/dilauroylphosphatidylcholine (TC8/DiC12PC) by Thermomyces lanuginosus lipase (TLL) and phospholipase A 2 (PLA 2 ) was studied by measuring the decrease of the surface area and change of the surface potential at barostatic conditions. The decrease of the surface area detects the transition of the substrate into reaction products and their solubilization while the change of the surface potential detects the contribution of dipole moment of the molecules remaining at the interface during the hydrolysis. The kinetic models, describing the interfacial hydrolysis allowed us to estimate the values of the global kinetic constants for TC8 and DiC12PC hydrolysis, respectively. The role of interaction between all participants of the catalytic act in that complex catalytic system is shown. The catalytic activity of TLL and PLA 2 is affected by the molecular environment in TC8/DiC12PC mixed monolayers.
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Hydrolysis of mixed Monomolecular Films of tricaprylin/dilauroylphosphatidylcholine by lipase and phospholipase A2
Colloids and Surfaces B: Biointerfaces, 2011Co-Authors: K Mircheva, I Panaiotov, Tz Ivanova, Robert VergerAbstract:Abstract The purpose of this article was to describe the kinetics of the enzymatic action of one or more enzymes on mixture of substrates organized in 2D structures in order to mimic some situations existing in biological or industrial systems. Hydrolysis of the mixed Monomolecular Films of tricaprylin/dilauroylphosphatidylcholine (TC8/DiC12PC) by Thermomyces lanuginosus lipase (TLL) and phospholipase A 2 (PLA 2 ) was studied by measuring the decrease of the surface area and change of the surface potential at barostatic conditions. The decrease of the surface area detects the transition of the substrate into reaction products and their solubilization while the change of the surface potential detects the contribution of dipole moment of the molecules remaining at the interface during the hydrolysis. The kinetic models, describing the interfacial hydrolysis allowed us to estimate the values of the global kinetic constants for TC8 and DiC12PC hydrolysis, respectively. The role of interaction between all participants of the catalytic act in that complex catalytic system is shown. The catalytic activity of TLL and PLA 2 is affected by the molecular environment in TC8/DiC12PC mixed monolayers.
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action of humicola lanuginosa lipase on mixed Monomolecular Films of tricaprylin and polyethylene glycol stearate
Colloids and Surfaces B: Biointerfaces, 2008Co-Authors: Tz Ivanova, K Mircheva, G Dobreva, I Panaiotov, J E Proust, Robert VergerAbstract:Abstract The hydrolysis catalyzed by Humicola lanuginosa lipase (HLL) of pure tricaprylin (TC) or stearate of polyethylene glycol 1500 (PEG-St) as well as their mixtures spread as Monomolecular Films were studied. The catalytic transformation of the two substrates TC or PEG-St into their respective reaction products was detected by measuring simultaneously the decrease in the film area and the surface potential using the “zero order” trough at constant surface pressure. A kinetic model describing the enzymatic hydrolysis was developed. The surface concentrations of the two substrates and their respective reaction products as well as the values of the global kinetic constants of hydrolysis were determined. The experimentally obtained global kinetic constants of the catalytic action of HLL against TC and PEG-St present in mixed monolayers of TC/PEG-St are approximately the same as in the case of pure monolayers. These obtained results give some indications that the activity of enzyme is not significantly affected by the different molecular environments in the mixed monolayers.
Tz Ivanova - One of the best experts on this subject based on the ideXlab platform.
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hydrolysis of mixed Monomolecular Films of tricaprylin dilauroylphosphatidylcholine by lipase and phospholipase a2
Colloids and Surfaces B: Biointerfaces, 2011Co-Authors: K Mircheva, I Panaiotov, Tz Ivanova, Robert VergerAbstract:Abstract The purpose of this article was to describe the kinetics of the enzymatic action of one or more enzymes on mixture of substrates organized in 2D structures in order to mimic some situations existing in biological or industrial systems. Hydrolysis of the mixed Monomolecular Films of tricaprylin/dilauroylphosphatidylcholine (TC8/DiC12PC) by Thermomyces lanuginosus lipase (TLL) and phospholipase A 2 (PLA 2 ) was studied by measuring the decrease of the surface area and change of the surface potential at barostatic conditions. The decrease of the surface area detects the transition of the substrate into reaction products and their solubilization while the change of the surface potential detects the contribution of dipole moment of the molecules remaining at the interface during the hydrolysis. The kinetic models, describing the interfacial hydrolysis allowed us to estimate the values of the global kinetic constants for TC8 and DiC12PC hydrolysis, respectively. The role of interaction between all participants of the catalytic act in that complex catalytic system is shown. The catalytic activity of TLL and PLA 2 is affected by the molecular environment in TC8/DiC12PC mixed monolayers.
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Hydrolysis of mixed Monomolecular Films of tricaprylin/dilauroylphosphatidylcholine by lipase and phospholipase A2
Colloids and Surfaces B: Biointerfaces, 2011Co-Authors: K Mircheva, I Panaiotov, Tz Ivanova, Robert VergerAbstract:Abstract The purpose of this article was to describe the kinetics of the enzymatic action of one or more enzymes on mixture of substrates organized in 2D structures in order to mimic some situations existing in biological or industrial systems. Hydrolysis of the mixed Monomolecular Films of tricaprylin/dilauroylphosphatidylcholine (TC8/DiC12PC) by Thermomyces lanuginosus lipase (TLL) and phospholipase A 2 (PLA 2 ) was studied by measuring the decrease of the surface area and change of the surface potential at barostatic conditions. The decrease of the surface area detects the transition of the substrate into reaction products and their solubilization while the change of the surface potential detects the contribution of dipole moment of the molecules remaining at the interface during the hydrolysis. The kinetic models, describing the interfacial hydrolysis allowed us to estimate the values of the global kinetic constants for TC8 and DiC12PC hydrolysis, respectively. The role of interaction between all participants of the catalytic act in that complex catalytic system is shown. The catalytic activity of TLL and PLA 2 is affected by the molecular environment in TC8/DiC12PC mixed monolayers.
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action of humicola lanuginosa lipase on mixed Monomolecular Films of tricaprylin and polyethylene glycol stearate
Colloids and Surfaces B: Biointerfaces, 2008Co-Authors: Tz Ivanova, K Mircheva, G Dobreva, I Panaiotov, J E Proust, Robert VergerAbstract:Abstract The hydrolysis catalyzed by Humicola lanuginosa lipase (HLL) of pure tricaprylin (TC) or stearate of polyethylene glycol 1500 (PEG-St) as well as their mixtures spread as Monomolecular Films were studied. The catalytic transformation of the two substrates TC or PEG-St into their respective reaction products was detected by measuring simultaneously the decrease in the film area and the surface potential using the “zero order” trough at constant surface pressure. A kinetic model describing the enzymatic hydrolysis was developed. The surface concentrations of the two substrates and their respective reaction products as well as the values of the global kinetic constants of hydrolysis were determined. The experimentally obtained global kinetic constants of the catalytic action of HLL against TC and PEG-St present in mixed monolayers of TC/PEG-St are approximately the same as in the case of pure monolayers. These obtained results give some indications that the activity of enzyme is not significantly affected by the different molecular environments in the mixed monolayers.
I Panaiotov - One of the best experts on this subject based on the ideXlab platform.
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hydrolysis of mixed Monomolecular Films of tricaprylin dilauroylphosphatidylcholine by lipase and phospholipase a2
Colloids and Surfaces B: Biointerfaces, 2011Co-Authors: K Mircheva, I Panaiotov, Tz Ivanova, Robert VergerAbstract:Abstract The purpose of this article was to describe the kinetics of the enzymatic action of one or more enzymes on mixture of substrates organized in 2D structures in order to mimic some situations existing in biological or industrial systems. Hydrolysis of the mixed Monomolecular Films of tricaprylin/dilauroylphosphatidylcholine (TC8/DiC12PC) by Thermomyces lanuginosus lipase (TLL) and phospholipase A 2 (PLA 2 ) was studied by measuring the decrease of the surface area and change of the surface potential at barostatic conditions. The decrease of the surface area detects the transition of the substrate into reaction products and their solubilization while the change of the surface potential detects the contribution of dipole moment of the molecules remaining at the interface during the hydrolysis. The kinetic models, describing the interfacial hydrolysis allowed us to estimate the values of the global kinetic constants for TC8 and DiC12PC hydrolysis, respectively. The role of interaction between all participants of the catalytic act in that complex catalytic system is shown. The catalytic activity of TLL and PLA 2 is affected by the molecular environment in TC8/DiC12PC mixed monolayers.
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Hydrolysis of mixed Monomolecular Films of tricaprylin/dilauroylphosphatidylcholine by lipase and phospholipase A2
Colloids and Surfaces B: Biointerfaces, 2011Co-Authors: K Mircheva, I Panaiotov, Tz Ivanova, Robert VergerAbstract:Abstract The purpose of this article was to describe the kinetics of the enzymatic action of one or more enzymes on mixture of substrates organized in 2D structures in order to mimic some situations existing in biological or industrial systems. Hydrolysis of the mixed Monomolecular Films of tricaprylin/dilauroylphosphatidylcholine (TC8/DiC12PC) by Thermomyces lanuginosus lipase (TLL) and phospholipase A 2 (PLA 2 ) was studied by measuring the decrease of the surface area and change of the surface potential at barostatic conditions. The decrease of the surface area detects the transition of the substrate into reaction products and their solubilization while the change of the surface potential detects the contribution of dipole moment of the molecules remaining at the interface during the hydrolysis. The kinetic models, describing the interfacial hydrolysis allowed us to estimate the values of the global kinetic constants for TC8 and DiC12PC hydrolysis, respectively. The role of interaction between all participants of the catalytic act in that complex catalytic system is shown. The catalytic activity of TLL and PLA 2 is affected by the molecular environment in TC8/DiC12PC mixed monolayers.
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hydrolysis of Monomolecular Films of long chain phosphatidylcholine by phospholipase a2 in the presence of β cyclodextrin
Colloids and Surfaces B: Biointerfaces, 1996Co-Authors: M Ivanova, Tzvetanka Ivanova, Robert Verger, I PanaiotovAbstract:Abstract The desorption rates of Monomolecular Films of oleic acid (OA) and lysophosphatidylcholine (lyso PC) at the air/water interface by water soluble β-cyclodextrin (β-CD) were studied. The desorption of OA and lyso PC involves the complexation of the single acyl chain into the β-CD cavity and the solubilization of the β-CD/OA or β-CD/lyso PC complex into the aqueous subphase, associated with a rapid decrease in the surface pressure. In the case of Monomolecular Films of egg phosphatidylcholine (egg PC), 1,2-dihexadecanoyl- sn -glycero-3-phosphatidylcholine (DPPC); 1,2-di( cis -9-octadecenoyl)- sn -glycero-3-phosphatidycholine (DOPC), no detectable changes in the surface pressure occurred after β-CD injection into the subphase. The hydrolysis of medium and long chain PC Monomolecular Films by phospholipase A 2 (PLA 2 ) was investigated in the absence of β-CD in the subphase. The considerable difference between the apparent kinetic constants was attributed to physical steps possibly involving molecular reorganization in the interface of long chain lipolytic products, associated with enzyme product inhibition. In the presence of β-CD in the subphase, the enzymatic hydrolysis of Monomolecular Films of long chain PC was found to have kinetic constants which were comparable to those measured with medium chain lipids. Furthermore, comparisons between the desorption rates of the β-CD/lipolytic product complexes and the enzymatic hydrolysis rates of long chain PC, in the presence of β-CD in the aqueous subphase, showed that the rate limiting step is neither the formation of the β-CD/lipolytic product complexes nor their desorption into the water subphase but the hydrolysis of the PC Monomolecular Films by PLA 2 . The presence of β-CD in the water subphase made it possible for the first time to perform kinetic measurements on the rates of hydrolysis of Monomolecular Films long chain PC by PLA 2 .
Margarita G Ivanova - One of the best experts on this subject based on the ideXlab platform.
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surface fluorescence resonance energy transfer studies on interfacial adsorption of thermomyces humicola lanuginosa lipase using Monomolecular Films of cis parinaric acid
Biopolymers, 2002Co-Authors: S Yapoudjian, Margarita G Ivanova, Isabelle Douchet, A Zenatti, M Sentis, W Marine, Allan Svendsen, Robert VergerAbstract:The fluorescence resonance energy transfer (FRET) technique was adapted to study the process whereby lipase is adsorbed to Monomolecular lipid Films spread at the air–water interface. When cis-parinaric acid (cis-PnA) was spread over an aqueous subphase before the injection of sodium taurodeoxycholate (NaTDC) and Thermomyces lanuginosa lipase (TLL), no FRET was observed. Under these conditions, no adsorption of TLL was detected using an ELISA. In contrast, FRET occurred when cis-PnA was spread over an aqueous subphase containing NaTDC and TLL. The FRET signals observed were attributed to the interactions between the adsorbed TLL and the cis-PnA Monomolecular Films. Comparisons between the fluorescence emission spectra corresponding to the bulk phase and the aspirated film, in the presence and absence of TLL, showed that cis-PnA was undetectable in the bulk phase. We concluded that the FRET originated from the interface and not from the bulk phase. Using surface FRET, we estimated that the surface excess of the catalytically inactive mutant, TLL(S146A), was 1.6 higher than that present in the wild-type TLL. This finding is in agreement with independent measurements of the surface excess of TLL and TLL(S146A) on Monomolecular Films of cis-PnA. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 65: 121–128, 2002
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interactions between β cyclodextrin and insoluble glyceride Monomolecular Films at the argon water interface application to lipase kinetics
Chemistry and Physics of Lipids, 1994Co-Authors: Serge Laurent, Margarita G Ivanova, Daniel Pioch, Jean Graille, Robert VergerAbstract:Abstract A study of the desorption rate of insoluble Monomolecular Films of oleic acid (OA), monoolein (MO), 1,2-diolein (1,2-DO), 1,3-diolein (1,3-DO) and triolein (TO) at the argon/water interface by water-soluble β-cyclodextrin (β-CD) is reported. The desorption of OA and MO involves probably the complexation of the single acyl chain with β-CD and sequestering of the formed soluble OA/β-CD and MO/β-CD complexes from the argon/water interface. In the case of monolayers of multiple acyl chain molecules such as DO and TO, no detectable change in the surface pressure occurred after β-CD injection. The surface rheological dilatational properties of the monolayers of DO and TO in the presence of β-CD in the subphase were studied. The elasticity of the DO monolayer remained unchanged, whereas the decrease in the surface elasticity of the TO film was attributed to the formation of a water-insoluble TO/β-CD complex. With the ‘tuning fork’ model, one acyl chain of TO can be included in the β-CD cavity. The formed TO/β-CD complex present at the interface retarded the propagation of the dilatational deformation along the plane of the monolayer. Schematic models have been proposed in an attempt to explain the different complexation of these lipids by β-CD at the argon/water interface. In addition to the above results, the presence of β-CD in the water subphase makes it possible for the first time to perform kinetic measurements of the lipase hydrolysis rates of long-chain glycerides forming Monomolecular Films.
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Interactions between β-cyclodextrin and insoluble glyceride Monomolecular Films at the argon/water interface: application to lipase kinetics
Chemistry and Physics of Lipids, 1994Co-Authors: Serge Laurent, Margarita G Ivanova, Daniel Pioch, Jean Graille, Robert VergerAbstract:Abstract A study of the desorption rate of insoluble Monomolecular Films of oleic acid (OA), monoolein (MO), 1,2-diolein (1,2-DO), 1,3-diolein (1,3-DO) and triolein (TO) at the argon/water interface by water-soluble β-cyclodextrin (β-CD) is reported. The desorption of OA and MO involves probably the complexation of the single acyl chain with β-CD and sequestering of the formed soluble OA/β-CD and MO/β-CD complexes from the argon/water interface. In the case of monolayers of multiple acyl chain molecules such as DO and TO, no detectable change in the surface pressure occurred after β-CD injection. The surface rheological dilatational properties of the monolayers of DO and TO in the presence of β-CD in the subphase were studied. The elasticity of the DO monolayer remained unchanged, whereas the decrease in the surface elasticity of the TO film was attributed to the formation of a water-insoluble TO/β-CD complex. With the ‘tuning fork’ model, one acyl chain of TO can be included in the β-CD cavity. The formed TO/β-CD complex present at the interface retarded the propagation of the dilatational deformation along the plane of the monolayer. Schematic models have been proposed in an attempt to explain the different complexation of these lipids by β-CD at the argon/water interface. In addition to the above results, the presence of β-CD in the water subphase makes it possible for the first time to perform kinetic measurements of the lipase hydrolysis rates of long-chain glycerides forming Monomolecular Films.