Denis Josse - Academia.edu (original) (raw)
Papers by Denis Josse
Simulation plays a major in the conception, the optimization and the certification of complex sys... more Simulation plays a major in the conception, the optimization and the certification of complex systems. Of particular interest here is the calibration of the parameters of computer models from high-dimensional physical observations. When the run times of these computer codes is high, this work focuses on the numerical challenges associated with the statistical inference. In particular, several adaptations of the Gaussian Process Regression (GPR) to the high-dimensional or functional output case are presented for the emulation of computer codes from limited data. Then, an adaptive procedure is detailed to minimize the calibration parameters uncertainty at the minimal computational cost. The proposed method is eventually applied to two applications that are based on dynamic simulators.
L'invention se rapporte au domaine des necessites de la vie et en particulier au domaine de l... more L'invention se rapporte au domaine des necessites de la vie et en particulier au domaine de la dermocosmetique.Elle concerne specifiquement des compositions dermatologiques ou cosmetiques associant pour un effet barriere epidermique un homopolymere de N-Vinyl 2-pyrolidone ou un copolymere de vinylpyrolidone / triacontene ou de vinylpyrolidone / eicosene avec un copolymere de 2-methacryloyloxyethyl phosphorylcholine / methacrylate d'alkyle, ou un copolymere de 2-methacryloyloxy ethylphosphorylcholine / chlorure de 2-hydroxy 3-methacryloyloxypropyl trimethylammonium dans une composition topique dermoprotectrice.Utilisation des compositions dermatologiques et / ou cosmetiques pour assurer la protection cutanee contre les agents chimiques toxiques de la famille des composes organophosphores et contre les agents chimiques de la famille des yperites.
The invention relates to a compound formed by micro- or nanoparticles functionalized associated c... more The invention relates to a compound formed by micro- or nanoparticles functionalized associated covalently to rheology modifying polymers. The invention is characterized in that the micro- or nanoparticles are functionalized micro- or nanoparticles functionalized ceria (CeO2) having a nominal diameter of between 1 and 1500 nm; and in that the rheology modifying polymers or adapters are selected from non-associative polymers or associative polymers. The invention applies to the protection or skin decontamination.
Issues in Toxicology, 2013
In a scenario of military or civilian exposure to chemical warfare agents (CWA), emergency proced... more In a scenario of military or civilian exposure to chemical warfare agents (CWA), emergency procedures include immediate body surface decontamination. The objectives of immediate decontamination are to remove as much contamination as possible from the body surface, including clothes. The resulting level of contamination should be low enough to allow the victims survival and to limit irreversible damage of victims' skin, eyes, and mucosal membranes.
Chemico-Biological Interactions
Military Medical Science Letters
The purpose of this study was to assess the ability of selected detergents (althosan MB 50%, trit... more The purpose of this study was to assess the ability of selected detergents (althosan MB 50%, triton X) and one commercial decontamination mean (Argos™) to permeate the pig skin, which could indicate a potential toxic side effect of mass casualty decontaminants. A method of static diffusion cells and UV spectrometry was used to evaluate the skin permeation. All tested agents did not permeate the skin in detectable amounts as 5% water solutions. In concentrated form, triton X and Argos™ did not permeate the skin whereas althosan MB 50% shown specific permeation rate of 6.134 µg.cm-1 in 24 hours.
![Research paper thumbnail of [Evaluation of coronary risk: a new technique of measuring lipoprotein (a)]](https://attachments.academia-assets.com/72419537/thumbnails/1.jpg)
](Archives des maladies du coeur et des vaisseaux, 1995
The aim of this study was to assess the reliability of immuno-nephelemetric assay (INA) of lipopr... more The aim of this study was to assess the reliability of immuno-nephelemetric assay (INA) of lipoprotein (Lp(a)) compared with immuno-radiometric (IRMA) and immuno-enzymologic (ELISA) assays in a coronary (P1) and a non-coronary (P2) populations. The serums of 66 coronary subjects (P1) with an average age of 61.5 +/- 10 years and 137 non-coronary subjects (P2) with an average age of 54 +/- 12 years were analysed by the 3 techniques. The technical characteristics of the INA were: negligeable interference with plasminogen (PLG) (< 1/100) for PLG < 375 mg/l; excellent repeatability and reproducibility at low, medium and high concentrations, respectively 12.3 and 7.5%. 1.2 and 1.2%, 1.3 and 1.1%, low dependance on sample conservation (stable 5 days at +4 degrees C), excellent practicability (simple and quick automised analysis: 10 min). The linear correlations with the concentrations of Lp(a) were: excellent with INA/IRMA P1 and P2: 0.99; very good with INA/ELISA P1: 0.88 and P2: 0....
Chemosphere
Chemical warfare agents have been used to incapacitate, injure or kill people, in a context of wa... more Chemical warfare agents have been used to incapacitate, injure or kill people, in a context of war or terrorist attack. It has previously been shown that hair could trap the sulphur mustard simulants methyl salicylate and 2-chloroethyl ethyl sulphide. In order to investigate simulants persistency in hair after intense vapour exposure, their desorption kinetics were studied by using two complementary methods: hair residual content measurement and desorbed vapour monitoring. Results showed that both simulants were detected in air and could be recovered from hair 2 h after the end of exposure. Longer experiments with methyl salicylate showed that it could still be recovered from hair after 24 h. Our data were fitted with several kinetic models and best correlation was obtained with a bimodal first-order equation, suggesting a 2-step desorption kinetics model: initial fast regime followed by a slower desorption. 2-chloroethyl ethyl sulphide was also detected in the immediate environment after hair exposure for 2 h, and hair simulant content decreased by more than 80%. Our results showed that hair ability to release formerly trapped chemical toxics could lead to health hazard. Their persistency however confirmed the potentiality of hair analysis as a tool for chemical exposure assessment.
Chemico-Biological Interactions, 2016
Chemical warfare agents are an actual threat and victims' decontamination is a main concern when ... more Chemical warfare agents are an actual threat and victims' decontamination is a main concern when mass exposure occurs. Skin decontamination with current protocols has been widely documented, as well as surface decontamination. However, considering hair ability to trap chemicals in vapour phase, we investigated hair decontamination after exposure to sulphur mustard simulants methyl salicylate and 2chloroethyl ethyl sulphide. Four decontamination protocols were tested on hair, combining showering and emergency decontamination (use of Fuller's earth or Reactive Skin Decontamination Lotion RSDL ®). Both simulants were recovered from hair after treatment, but contents were significantly reduced (42 e85% content allowance). Showering alone was the least efficient protocol. Concerning 2-chloroethyl ethyl sulphide, protocols did not display significant differences in decontamination efficacy. For MeS, use of emergency decontaminants significantly increased showering efficacy (10e20% rise), underlining their usefulness before thorough decontamination. Our results highlighted the need to extensively decontaminate hair after chemical exposure. Residual amounts after decontamination are challenging, as their release from hair could lead to health issues.
Chemico-Biological Interactions, 2016
Organophosphorus compounds (OP), which mainly penetrate via the percutaneous pathway, represent a... more Organophosphorus compounds (OP), which mainly penetrate via the percutaneous pathway, represent a threat for both military and civilians. Body surface decontamination is vital to prevent victims poisoning. The development of a cost-effective formulation, which could be efficient and easy to handle in case of mass contamination, is therefore crucial. Metal oxides nanoparticles, due their large surface areas and the large amount of highly reactive sites, present high reactivity towards OP. First, this study aimed at evaluating the reaction of CeO2 nanoparticles, synthetized by microwave path and calcined at 500 or 600 °C, with Paraoxon (POX) in aqueous solution. Results showed that both nanoparticles degraded 60%-70% of POX. CeO2 calcined at 500 °C, owing to its larger specific area, was the most effective. Moreover, the degradation was significantly increased under Ultra-Violet irradiation (initial degradation rate doubled). Then, skin decontamination was studied in vitro using the Franz cell method with pig-ear skin samples. CeO2 powder and an aqueous suspension of CeO2 (CeO2-W) were applied 1 h after POX exposure. The efficiency of decontamination, including removal and/or degradation of POX, was compared to Fuller&amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s earth (FE) and RSDL lotion which are, currently, the most efficient systems for skin decontamination. CeO2-W and RSDL were the most efficient to remove POX from the skin surface and decrease skin absorption by 6.4 compared to the control not decontaminated. FE reduced significantly (twice) the absorbed fraction of POX, contrarily to CeO2 powder. Considering only the degradation rate of POX, the products ranged in the order CeO2 &amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; RSDL &amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; CeO2-W &amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; FE (no degradation). This study showed that CeO2 nanoparticles are a promising material for skin decontamination of OP if formulated as a dispersion able to remove POX like CeO2-W and to degrade it as CeO2 powder.
Toxicology in Vitro, 2016
This study aimed at developing innovative systems for skin decontamination. Pickering emulsions, ... more This study aimed at developing innovative systems for skin decontamination. Pickering emulsions, i.e. solid-stabilized emulsions, containing silica (S-PE) or Fuller&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s earth (FE-PE) were formulated. Their efficiency for skin decontamination was evaluated, in vitro, 45min after an exposure to VX, one of the most highly toxic chemical warfare agents. Pickering emulsions were compared to FE (FE-W) and silica (S-W) aqueous suspensions. PE containing an oil with a similar hydrophobicity to VX should promote its extraction. All the formulations reduced significantly the amount of VX quantified on and into the skin compared to the control. Wiping the skin surface with a pad already allowed removing more than half of VX. FE-W was the less efficient (85% of VX removed). The other formulations (FE-PE, S-PE and S-W) resulted in more than 90% of the quantity of VX removed. The charge of particles was the most influential factor. The low pH of formulations containing silica favored electrostatic interactions of VX with particles explaining the better elimination from the skin surface. Formulations containing FE had basic pH, and weak interactions with VX did not improve the skin decontamination. However, these low interactions between VX and FE promote the transfer of VX into the oil droplets in the FE-PE.
Chemico Biological Interactions, May 14, 1999
Serum paraoxonase (PON1, EC 3.1.8.1.) is a high density lipid-(HDL)-associated, calcium-dependent... more Serum paraoxonase (PON1, EC 3.1.8.1.) is a high density lipid-(HDL)-associated, calcium-dependent enzyme whose 3D structure, active site residues and physiological substrates are not known. The kinetic parameters k cat and K m (relative to k cat and K m of the wild-type), determined with four substrates (phenylacetate, paraoxon, diazoxon and chlorpyrifosoxon) were less than 1% and more than 100% for the W280A and W280F mutant enzymes, respectively. These results indicated that the aromatic/hydrophobic character of the amino acid in position 280 is essential for PON1 activity. In this study, we investigated whether this aromatic residue is in the PON1 active site. Group-specific labelling studies with N-bromosuccinimide, an oxidative agent of tryptophan, strongly suggested that one or several Trp could be in the active site of PON1 but we could not conclude either on the specificity of the labelling reaction or on the number of oxidized Trp. However, although PON activity was not altered by the hydrophilic tryptophan-modifying reagent 2-hydroxy-5-nitrobenzyl chloride (NBC), it was significantly reduced by the p-nitrophenylacetate analog 2-acetoxy-5-nitrobenzyl chloride (ANBC), whose hydrolysis by PON1 generated NBC in the active site. Moreover, since at least one calcium ion is present in the PON catalytic site, we attempted to probe the metal local environment using the calcium analog terbium. The luminescence spectrum of the PON-terbium complex exhibited an emission peak at 545 nm characteristic of an aromatic residue (Trp and/or Tyr)-terbium interaction. In conclusion, both the results obtained with the mechanism-based inhibitor of PON1 (ANBC) and the calcium-binding site luminescent probe terbium support the hypothesis of the presence of at least one Trp residue in the PON1 active site. Trp residue(s) may be involved in the binding of aromatic substrates.
In the search for new nerve agent scavengers the organophosphorus acid anhydride hydrolase (OPAA ... more In the search for new nerve agent scavengers the organophosphorus acid anhydride hydrolase (OPAA hydrolase) enzymes from human plasma (paraoxonase 1, PON1) have emerged as very promising candidates. Although the turnover rates of these enzymes are not believed to be high enough to confer a great amount of protection against nerve agents, it is probable that those rates can be improved by protein engineering once high-resolution crystal structures are available. It was previously shown that both known isozymes of PON1 are able to hydrolyze the toxic isomers of soman, sarin and, to a lesser extent, tabun. We now have shown that in spite of the rather high Km values of these enzymes with these agents, sarin and soman are hydrolyzed quite rapidly even at submicromolar concentrations. We have also demonstrated that the enzyme is able to catalyze the hydrolysis of VX. In contrast to the reactions with soman and sarin, both of which produced good Lineweaver-Burk plots from which Km and Vmax could be calculated, this reaction appears not to follow Michaelis-Menten kinetics; the rate of reaction continues to increase with substrate concentration at least up to 3.2 mM VX at which point the hydrolysis rate is 0.1 µmole per minute per mg enzyme, a value that is comparable to the value of 0.16 µmole per minute per mg enzyme reported for the hydrolysis of VX by the Co ++ form of the OPAA Hydrolase from Pseudomonas diminuta, the most efficient VX-hydrolyzing enzyme reported previously.
Simulation plays a major in the conception, the optimization and the certification of complex sys... more Simulation plays a major in the conception, the optimization and the certification of complex systems. Of particular interest here is the calibration of the parameters of computer models from high-dimensional physical observations. When the run times of these computer codes is high, this work focuses on the numerical challenges associated with the statistical inference. In particular, several adaptations of the Gaussian Process Regression (GPR) to the high-dimensional or functional output case are presented for the emulation of computer codes from limited data. Then, an adaptive procedure is detailed to minimize the calibration parameters uncertainty at the minimal computational cost. The proposed method is eventually applied to two applications that are based on dynamic simulators.
L'invention se rapporte au domaine des necessites de la vie et en particulier au domaine de l... more L'invention se rapporte au domaine des necessites de la vie et en particulier au domaine de la dermocosmetique.Elle concerne specifiquement des compositions dermatologiques ou cosmetiques associant pour un effet barriere epidermique un homopolymere de N-Vinyl 2-pyrolidone ou un copolymere de vinylpyrolidone / triacontene ou de vinylpyrolidone / eicosene avec un copolymere de 2-methacryloyloxyethyl phosphorylcholine / methacrylate d'alkyle, ou un copolymere de 2-methacryloyloxy ethylphosphorylcholine / chlorure de 2-hydroxy 3-methacryloyloxypropyl trimethylammonium dans une composition topique dermoprotectrice.Utilisation des compositions dermatologiques et / ou cosmetiques pour assurer la protection cutanee contre les agents chimiques toxiques de la famille des composes organophosphores et contre les agents chimiques de la famille des yperites.
The invention relates to a compound formed by micro- or nanoparticles functionalized associated c... more The invention relates to a compound formed by micro- or nanoparticles functionalized associated covalently to rheology modifying polymers. The invention is characterized in that the micro- or nanoparticles are functionalized micro- or nanoparticles functionalized ceria (CeO2) having a nominal diameter of between 1 and 1500 nm; and in that the rheology modifying polymers or adapters are selected from non-associative polymers or associative polymers. The invention applies to the protection or skin decontamination.
Issues in Toxicology, 2013
In a scenario of military or civilian exposure to chemical warfare agents (CWA), emergency proced... more In a scenario of military or civilian exposure to chemical warfare agents (CWA), emergency procedures include immediate body surface decontamination. The objectives of immediate decontamination are to remove as much contamination as possible from the body surface, including clothes. The resulting level of contamination should be low enough to allow the victims survival and to limit irreversible damage of victims' skin, eyes, and mucosal membranes.
Chemico-Biological Interactions
Military Medical Science Letters
The purpose of this study was to assess the ability of selected detergents (althosan MB 50%, trit... more The purpose of this study was to assess the ability of selected detergents (althosan MB 50%, triton X) and one commercial decontamination mean (Argos™) to permeate the pig skin, which could indicate a potential toxic side effect of mass casualty decontaminants. A method of static diffusion cells and UV spectrometry was used to evaluate the skin permeation. All tested agents did not permeate the skin in detectable amounts as 5% water solutions. In concentrated form, triton X and Argos™ did not permeate the skin whereas althosan MB 50% shown specific permeation rate of 6.134 µg.cm-1 in 24 hours.
Archives des maladies du coeur et des vaisseaux, 1995
The aim of this study was to assess the reliability of immuno-nephelemetric assay (INA) of lipopr... more The aim of this study was to assess the reliability of immuno-nephelemetric assay (INA) of lipoprotein (Lp(a)) compared with immuno-radiometric (IRMA) and immuno-enzymologic (ELISA) assays in a coronary (P1) and a non-coronary (P2) populations. The serums of 66 coronary subjects (P1) with an average age of 61.5 +/- 10 years and 137 non-coronary subjects (P2) with an average age of 54 +/- 12 years were analysed by the 3 techniques. The technical characteristics of the INA were: negligeable interference with plasminogen (PLG) (< 1/100) for PLG < 375 mg/l; excellent repeatability and reproducibility at low, medium and high concentrations, respectively 12.3 and 7.5%. 1.2 and 1.2%, 1.3 and 1.1%, low dependance on sample conservation (stable 5 days at +4 degrees C), excellent practicability (simple and quick automised analysis: 10 min). The linear correlations with the concentrations of Lp(a) were: excellent with INA/IRMA P1 and P2: 0.99; very good with INA/ELISA P1: 0.88 and P2: 0....
Chemosphere
Chemical warfare agents have been used to incapacitate, injure or kill people, in a context of wa... more Chemical warfare agents have been used to incapacitate, injure or kill people, in a context of war or terrorist attack. It has previously been shown that hair could trap the sulphur mustard simulants methyl salicylate and 2-chloroethyl ethyl sulphide. In order to investigate simulants persistency in hair after intense vapour exposure, their desorption kinetics were studied by using two complementary methods: hair residual content measurement and desorbed vapour monitoring. Results showed that both simulants were detected in air and could be recovered from hair 2 h after the end of exposure. Longer experiments with methyl salicylate showed that it could still be recovered from hair after 24 h. Our data were fitted with several kinetic models and best correlation was obtained with a bimodal first-order equation, suggesting a 2-step desorption kinetics model: initial fast regime followed by a slower desorption. 2-chloroethyl ethyl sulphide was also detected in the immediate environment after hair exposure for 2 h, and hair simulant content decreased by more than 80%. Our results showed that hair ability to release formerly trapped chemical toxics could lead to health hazard. Their persistency however confirmed the potentiality of hair analysis as a tool for chemical exposure assessment.
Chemico-Biological Interactions, 2016
Chemical warfare agents are an actual threat and victims' decontamination is a main concern when ... more Chemical warfare agents are an actual threat and victims' decontamination is a main concern when mass exposure occurs. Skin decontamination with current protocols has been widely documented, as well as surface decontamination. However, considering hair ability to trap chemicals in vapour phase, we investigated hair decontamination after exposure to sulphur mustard simulants methyl salicylate and 2chloroethyl ethyl sulphide. Four decontamination protocols were tested on hair, combining showering and emergency decontamination (use of Fuller's earth or Reactive Skin Decontamination Lotion RSDL ®). Both simulants were recovered from hair after treatment, but contents were significantly reduced (42 e85% content allowance). Showering alone was the least efficient protocol. Concerning 2-chloroethyl ethyl sulphide, protocols did not display significant differences in decontamination efficacy. For MeS, use of emergency decontaminants significantly increased showering efficacy (10e20% rise), underlining their usefulness before thorough decontamination. Our results highlighted the need to extensively decontaminate hair after chemical exposure. Residual amounts after decontamination are challenging, as their release from hair could lead to health issues.
Chemico-Biological Interactions, 2016
Organophosphorus compounds (OP), which mainly penetrate via the percutaneous pathway, represent a... more Organophosphorus compounds (OP), which mainly penetrate via the percutaneous pathway, represent a threat for both military and civilians. Body surface decontamination is vital to prevent victims poisoning. The development of a cost-effective formulation, which could be efficient and easy to handle in case of mass contamination, is therefore crucial. Metal oxides nanoparticles, due their large surface areas and the large amount of highly reactive sites, present high reactivity towards OP. First, this study aimed at evaluating the reaction of CeO2 nanoparticles, synthetized by microwave path and calcined at 500 or 600 °C, with Paraoxon (POX) in aqueous solution. Results showed that both nanoparticles degraded 60%-70% of POX. CeO2 calcined at 500 °C, owing to its larger specific area, was the most effective. Moreover, the degradation was significantly increased under Ultra-Violet irradiation (initial degradation rate doubled). Then, skin decontamination was studied in vitro using the Franz cell method with pig-ear skin samples. CeO2 powder and an aqueous suspension of CeO2 (CeO2-W) were applied 1 h after POX exposure. The efficiency of decontamination, including removal and/or degradation of POX, was compared to Fuller&amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s earth (FE) and RSDL lotion which are, currently, the most efficient systems for skin decontamination. CeO2-W and RSDL were the most efficient to remove POX from the skin surface and decrease skin absorption by 6.4 compared to the control not decontaminated. FE reduced significantly (twice) the absorbed fraction of POX, contrarily to CeO2 powder. Considering only the degradation rate of POX, the products ranged in the order CeO2 &amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; RSDL &amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; CeO2-W &amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; FE (no degradation). This study showed that CeO2 nanoparticles are a promising material for skin decontamination of OP if formulated as a dispersion able to remove POX like CeO2-W and to degrade it as CeO2 powder.
Toxicology in Vitro, 2016
This study aimed at developing innovative systems for skin decontamination. Pickering emulsions, ... more This study aimed at developing innovative systems for skin decontamination. Pickering emulsions, i.e. solid-stabilized emulsions, containing silica (S-PE) or Fuller&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s earth (FE-PE) were formulated. Their efficiency for skin decontamination was evaluated, in vitro, 45min after an exposure to VX, one of the most highly toxic chemical warfare agents. Pickering emulsions were compared to FE (FE-W) and silica (S-W) aqueous suspensions. PE containing an oil with a similar hydrophobicity to VX should promote its extraction. All the formulations reduced significantly the amount of VX quantified on and into the skin compared to the control. Wiping the skin surface with a pad already allowed removing more than half of VX. FE-W was the less efficient (85% of VX removed). The other formulations (FE-PE, S-PE and S-W) resulted in more than 90% of the quantity of VX removed. The charge of particles was the most influential factor. The low pH of formulations containing silica favored electrostatic interactions of VX with particles explaining the better elimination from the skin surface. Formulations containing FE had basic pH, and weak interactions with VX did not improve the skin decontamination. However, these low interactions between VX and FE promote the transfer of VX into the oil droplets in the FE-PE.
Chemico Biological Interactions, May 14, 1999
Serum paraoxonase (PON1, EC 3.1.8.1.) is a high density lipid-(HDL)-associated, calcium-dependent... more Serum paraoxonase (PON1, EC 3.1.8.1.) is a high density lipid-(HDL)-associated, calcium-dependent enzyme whose 3D structure, active site residues and physiological substrates are not known. The kinetic parameters k cat and K m (relative to k cat and K m of the wild-type), determined with four substrates (phenylacetate, paraoxon, diazoxon and chlorpyrifosoxon) were less than 1% and more than 100% for the W280A and W280F mutant enzymes, respectively. These results indicated that the aromatic/hydrophobic character of the amino acid in position 280 is essential for PON1 activity. In this study, we investigated whether this aromatic residue is in the PON1 active site. Group-specific labelling studies with N-bromosuccinimide, an oxidative agent of tryptophan, strongly suggested that one or several Trp could be in the active site of PON1 but we could not conclude either on the specificity of the labelling reaction or on the number of oxidized Trp. However, although PON activity was not altered by the hydrophilic tryptophan-modifying reagent 2-hydroxy-5-nitrobenzyl chloride (NBC), it was significantly reduced by the p-nitrophenylacetate analog 2-acetoxy-5-nitrobenzyl chloride (ANBC), whose hydrolysis by PON1 generated NBC in the active site. Moreover, since at least one calcium ion is present in the PON catalytic site, we attempted to probe the metal local environment using the calcium analog terbium. The luminescence spectrum of the PON-terbium complex exhibited an emission peak at 545 nm characteristic of an aromatic residue (Trp and/or Tyr)-terbium interaction. In conclusion, both the results obtained with the mechanism-based inhibitor of PON1 (ANBC) and the calcium-binding site luminescent probe terbium support the hypothesis of the presence of at least one Trp residue in the PON1 active site. Trp residue(s) may be involved in the binding of aromatic substrates.
In the search for new nerve agent scavengers the organophosphorus acid anhydride hydrolase (OPAA ... more In the search for new nerve agent scavengers the organophosphorus acid anhydride hydrolase (OPAA hydrolase) enzymes from human plasma (paraoxonase 1, PON1) have emerged as very promising candidates. Although the turnover rates of these enzymes are not believed to be high enough to confer a great amount of protection against nerve agents, it is probable that those rates can be improved by protein engineering once high-resolution crystal structures are available. It was previously shown that both known isozymes of PON1 are able to hydrolyze the toxic isomers of soman, sarin and, to a lesser extent, tabun. We now have shown that in spite of the rather high Km values of these enzymes with these agents, sarin and soman are hydrolyzed quite rapidly even at submicromolar concentrations. We have also demonstrated that the enzyme is able to catalyze the hydrolysis of VX. In contrast to the reactions with soman and sarin, both of which produced good Lineweaver-Burk plots from which Km and Vmax could be calculated, this reaction appears not to follow Michaelis-Menten kinetics; the rate of reaction continues to increase with substrate concentration at least up to 3.2 mM VX at which point the hydrolysis rate is 0.1 µmole per minute per mg enzyme, a value that is comparable to the value of 0.16 µmole per minute per mg enzyme reported for the hydrolysis of VX by the Co ++ form of the OPAA Hydrolase from Pseudomonas diminuta, the most efficient VX-hydrolyzing enzyme reported previously.