The Experts below are selected from a list of 8688 Experts worldwide ranked by ideXlab platform
Réjean Beaudet - One of the best experts on this subject based on the ideXlab platform.
-
purification and characterization of prba a new esterase from enterobacter cloacae hydrolyzing the esters of 4 Hydroxybenzoic Acid parabens
Journal of Biological Chemistry, 2003Co-Authors: Nelly Valkova, François Lépine, Maryse Dupont, Louisette Labrie, Réjean BeaudetAbstract:The esterase PrbA from Enterobacter cloacae strain EM has previously been shown to confer additional resistance to the esters of 4-Hydroxybenzoic Acid (parabens) to two species of Enterobacter. The PrbA protein has been purified from E. cloacae strain EM using a three-step protocol resulting in a 60-fold increase in specific activity. The molecular mass of the mature enzyme was determined to be 54,619 +/- 1 Da by mass spectrometry. It is highly active against a series of parabens with alkyl groups ranging from methyl to butyl, with K(m) and V(max) values ranging from 0.45 to 0.88 mM and 0.031 to 0.15 mM/min, respectively. The K(m) and V(max) values for p-nitrophenyl acetate were 3.7 mM and 0.051 mM/min. PrbA hydrolyzed a variety of structurally analogous compounds, with activities larger than 20% relative to propyl paraben for methyl 3-hydroxybenzoate, methyl 4-aminobenzoate, or methyl vanillate. The enzyme showed optimum activity at 31 degrees C and at pH 7.0. PrbA was able to transesterify parabens with alcohols of increasing chain length from methanol to n-butanol, achieving 64% transesterification of 0.5 mm propyl paraben with 5% methanol within 2 h. PrbA was inhibited by 1-chloro-3-tosylamido-4-phenyl-2-butanone and 1-chloro-3-tosylamido-7-amino-2-heptanone (TLCK), with K(i) values of 0.29 and 0.20 mM, respectively, and was irreversibly inhibited by Diisopropyl fluorophosphate (DFP) or diethyl pyrocarbonate. The stoichiometry of addition of DFP to the enzyme was 1:1 and only 1 TLCK molecule was found in TLCK-modified enzyme, as measured by mass spectrometry. Analysis of the tryptic digest of the DFP-modified PrbA demonstrated that the addition of a DFP molecule occurred at Ser-189, indicating the location of the active serine.
-
purification and characterization of prba a new esterase from enterobacter cloacae hydrolyzing the esters of 4 Hydroxybenzoic Acid parabens
Journal of Biological Chemistry, 2003Co-Authors: Nelly Valkova, François Lépine, Maryse Dupont, Louisette Labrie, Réjean BeaudetAbstract:Abstract The esterase PrbA from Enterobacter cloacae strain EM has previously been shown to confer additional resistance to the esters of 4-Hydroxybenzoic Acid (parabens) to two species of Enterobacter. The PrbA protein has been purified from E. cloacae strain EM using a three-step protocol resulting in a 60-fold increase in specific activity. The molecular mass of the mature enzyme was determined to be 54,619 ± 1 Da by mass spectrometry. It is highly active against a series of parabens with alkyl groups ranging from methyl to butyl, withK m and V max values ranging from 0.45 to 0.88 mm and 0.031 to 0.15 mm/min, respectively. The K m andV max values for p-nitrophenyl acetate were 3.7 mm and 0.051 mm/min. PrbA hydrolyzed a variety of structurally analogous compounds, with activities larger than 20% relative to propyl paraben for methyl 3-hydroxybenzoate, methyl 4-aminobenzoate, or methyl vanillate. The enzyme showed optimum activity at 31 °C and at pH 7.0. PrbA was able to transesterify parabens with alcohols of increasing chain length from methanol to n-butanol, achieving 64% transesterification of 0.5 mm propyl paraben with 5% methanol within 2 h. PrbA was inhibited by 1-chloro-3-tosylamido-4-phenyl-2-butanone and 1-chloro-3-tosylamido-7- amino-2-heptanone (TLCK), withK i values of 0.29 and 0.20 mm, respectively, and was irreversibly inhibited by Diisopropyl fluorophosphate (DFP) or diethyl pyrocarbonate. The stoichiometry of addition of DFP to the enzyme was 1:1 and only 1 TLCK molecule was found in TLCK-modified enzyme, as measured by mass spectrometry. Analysis of the tryptic digest of the DFP-modified PrbA demonstrated that the addition of a DFP molecule occurred at Ser-189, indicating the location of the active serine.
-
Hydrolysis of 4-Hydroxybenzoic Acid Esters (Parabens) and Their Aerobic Transformation into Phenol by the Resistant Enterobacter cloacae Strain EM
Applied and environmental microbiology, 2001Co-Authors: Nelly Valkova, François Lépine, Loredana Valeanu, Maryse Dupont, Louisette Labrie, J.-g. Bisaillon, Réjean Beaudet, François Shareck, Richard VillemurAbstract:Enterobacter cloacae strain EM was isolated from a commercial dietary mineral supplement stabilized by a mixture of methylparaben and propylparaben. It harbored a high-molecular-weight plasmid and was resistant to high concentrations of parabens. Strain EM was able to grow in liquid media containing similar amounts of parabens as found in the mineral supplement (1,700 and 180 mg of methyl and propylparaben, respectively, per liter or 11.2 and 1.0 mM) and in very high concentrations of methylparaben (3,000 mg liter−1, or 19.7 mM). This strain was able to hydrolyze approximately 500 mg of methyl-, ethyl-, or propylparaben liter−1 (3 mM) in less than 2 h in liquid culture, and the supernatant of a sonicated culture, after a 30-fold dilution, was able to hydrolyze 1,000 mg of methylparaben liter−1 (6.6 mM) in 15 min. The first step of paraben degradation was the hydrolysis of the ester bond to produce 4-Hydroxybenzoic Acid, followed by a decarboxylation step to produce phenol under aerobic conditions. The transformation of 4-Hydroxybenzoic Acid into phenol was stoichiometric. The conversion of approximately 500 mg of parabens liter−1 (3 mM) to phenol in liquid culture was completed within 5 h without significant hindrance to the growth of strain EM, while higher concentrations of parabens partially inhibited its growth.
Nelly Valkova - One of the best experts on this subject based on the ideXlab platform.
-
purification and characterization of prba a new esterase from enterobacter cloacae hydrolyzing the esters of 4 Hydroxybenzoic Acid parabens
Journal of Biological Chemistry, 2003Co-Authors: Nelly Valkova, François Lépine, Maryse Dupont, Louisette Labrie, Réjean BeaudetAbstract:The esterase PrbA from Enterobacter cloacae strain EM has previously been shown to confer additional resistance to the esters of 4-Hydroxybenzoic Acid (parabens) to two species of Enterobacter. The PrbA protein has been purified from E. cloacae strain EM using a three-step protocol resulting in a 60-fold increase in specific activity. The molecular mass of the mature enzyme was determined to be 54,619 +/- 1 Da by mass spectrometry. It is highly active against a series of parabens with alkyl groups ranging from methyl to butyl, with K(m) and V(max) values ranging from 0.45 to 0.88 mM and 0.031 to 0.15 mM/min, respectively. The K(m) and V(max) values for p-nitrophenyl acetate were 3.7 mM and 0.051 mM/min. PrbA hydrolyzed a variety of structurally analogous compounds, with activities larger than 20% relative to propyl paraben for methyl 3-hydroxybenzoate, methyl 4-aminobenzoate, or methyl vanillate. The enzyme showed optimum activity at 31 degrees C and at pH 7.0. PrbA was able to transesterify parabens with alcohols of increasing chain length from methanol to n-butanol, achieving 64% transesterification of 0.5 mm propyl paraben with 5% methanol within 2 h. PrbA was inhibited by 1-chloro-3-tosylamido-4-phenyl-2-butanone and 1-chloro-3-tosylamido-7-amino-2-heptanone (TLCK), with K(i) values of 0.29 and 0.20 mM, respectively, and was irreversibly inhibited by Diisopropyl fluorophosphate (DFP) or diethyl pyrocarbonate. The stoichiometry of addition of DFP to the enzyme was 1:1 and only 1 TLCK molecule was found in TLCK-modified enzyme, as measured by mass spectrometry. Analysis of the tryptic digest of the DFP-modified PrbA demonstrated that the addition of a DFP molecule occurred at Ser-189, indicating the location of the active serine.
-
purification and characterization of prba a new esterase from enterobacter cloacae hydrolyzing the esters of 4 Hydroxybenzoic Acid parabens
Journal of Biological Chemistry, 2003Co-Authors: Nelly Valkova, François Lépine, Maryse Dupont, Louisette Labrie, Réjean BeaudetAbstract:Abstract The esterase PrbA from Enterobacter cloacae strain EM has previously been shown to confer additional resistance to the esters of 4-Hydroxybenzoic Acid (parabens) to two species of Enterobacter. The PrbA protein has been purified from E. cloacae strain EM using a three-step protocol resulting in a 60-fold increase in specific activity. The molecular mass of the mature enzyme was determined to be 54,619 ± 1 Da by mass spectrometry. It is highly active against a series of parabens with alkyl groups ranging from methyl to butyl, withK m and V max values ranging from 0.45 to 0.88 mm and 0.031 to 0.15 mm/min, respectively. The K m andV max values for p-nitrophenyl acetate were 3.7 mm and 0.051 mm/min. PrbA hydrolyzed a variety of structurally analogous compounds, with activities larger than 20% relative to propyl paraben for methyl 3-hydroxybenzoate, methyl 4-aminobenzoate, or methyl vanillate. The enzyme showed optimum activity at 31 °C and at pH 7.0. PrbA was able to transesterify parabens with alcohols of increasing chain length from methanol to n-butanol, achieving 64% transesterification of 0.5 mm propyl paraben with 5% methanol within 2 h. PrbA was inhibited by 1-chloro-3-tosylamido-4-phenyl-2-butanone and 1-chloro-3-tosylamido-7- amino-2-heptanone (TLCK), withK i values of 0.29 and 0.20 mm, respectively, and was irreversibly inhibited by Diisopropyl fluorophosphate (DFP) or diethyl pyrocarbonate. The stoichiometry of addition of DFP to the enzyme was 1:1 and only 1 TLCK molecule was found in TLCK-modified enzyme, as measured by mass spectrometry. Analysis of the tryptic digest of the DFP-modified PrbA demonstrated that the addition of a DFP molecule occurred at Ser-189, indicating the location of the active serine.
-
Hydrolysis of 4-Hydroxybenzoic Acid Esters (Parabens) and Their Aerobic Transformation into Phenol by the Resistant Enterobacter cloacae Strain EM
Applied and environmental microbiology, 2001Co-Authors: Nelly Valkova, François Lépine, Loredana Valeanu, Maryse Dupont, Louisette Labrie, J.-g. Bisaillon, Réjean Beaudet, François Shareck, Richard VillemurAbstract:Enterobacter cloacae strain EM was isolated from a commercial dietary mineral supplement stabilized by a mixture of methylparaben and propylparaben. It harbored a high-molecular-weight plasmid and was resistant to high concentrations of parabens. Strain EM was able to grow in liquid media containing similar amounts of parabens as found in the mineral supplement (1,700 and 180 mg of methyl and propylparaben, respectively, per liter or 11.2 and 1.0 mM) and in very high concentrations of methylparaben (3,000 mg liter−1, or 19.7 mM). This strain was able to hydrolyze approximately 500 mg of methyl-, ethyl-, or propylparaben liter−1 (3 mM) in less than 2 h in liquid culture, and the supernatant of a sonicated culture, after a 30-fold dilution, was able to hydrolyze 1,000 mg of methylparaben liter−1 (6.6 mM) in 15 min. The first step of paraben degradation was the hydrolysis of the ester bond to produce 4-Hydroxybenzoic Acid, followed by a decarboxylation step to produce phenol under aerobic conditions. The transformation of 4-Hydroxybenzoic Acid into phenol was stoichiometric. The conversion of approximately 500 mg of parabens liter−1 (3 mM) to phenol in liquid culture was completed within 5 h without significant hindrance to the growth of strain EM, while higher concentrations of parabens partially inhibited its growth.
Chuanxiang Chen - One of the best experts on this subject based on the ideXlab platform.
-
electrosynthesis of poly 3 amino 4 Hydroxybenzoic Acid nanoparticles with electroactivity even in highly alkaline solutions
Journal of Applied Polymer Science, 2015Co-Authors: Chuanxiang Chen, Xiaozhang Hong, Yuhua GaoAbstract:Electroactive poly(3-amino-4-Hydroxybenzoic Acid) nanoparticles were synthesized using cyclic voltammetry and exhibited high electroactivity in 0.30 M Na2SO4 solutions with pH values ranging from 1.0 to 12.0. This indicates that polymer has excellent electrochemical properties even in near-neutral and alkaline solutions compared to polyaniline. The anodic and cathodic peak currents of the polymer increase linearly with the square root of scan rate from 5 to 150 mV s−1, indicating that the electrode reaction is controlled by a diffusion process. The structure of the polymer was investigated using UV–visible spectroscopy, Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and X-ray photoelectron spectroscopy. Based on the spectroscopic measurements, a possible polymerization mechanism of 3-amino-4-Hydroxybenzoic Acid was proposed. The polymer surface morphology was characterized by scanning electron microscopy. The enhanced electrochemical properties are ascribed to the synergistic effect of COOH and OH groups in the polymer chains. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42190.
-
synthesis of poly aniline co 3 amino 4 Hydroxybenzoic Acid and its enhanced redox activity under highly basic conditions
Electrochimica Acta, 2013Co-Authors: Chuanxiang Chen, Guoqiang Ding, Dan ZhouAbstract:Abstract Poly(aniline- co -3-amino-4-Hydroxybenzoic Acid) was synthesized using cyclic voltammetry. The monomer concentration ratio and applied potential strongly affect the copolymerization rate and electrochemical properties of the copolymer. The results from the infrared spectrum (IR) and X-ray photoelectron spectroscopy (XPS) of the copolymer demonstrate that 3-amino-4-Hydroxybenzoic Acid units are incorporated into the copolymer chain and that SO 4 2− ions can be doped into the copolymer film during the electrochemical copolymerization. The scanning electron microscopy (SEM) micrograph proves that the copolymer film has a nanostructured network of mass interwoven fibers with a diameter of 10–50 nm. The copolymer obtained at the optimum conditions exhibits excellent redox activity in a 0.30 M Na 2 SO 4 aqueous solution (pH 11.0), which is superior to that of polyaniline itself. The improvement can be attributed to the synergistic effect of the COOH and OH functional groups in the copolymer chain.
Tatsuo Kaneko - One of the best experts on this subject based on the ideXlab platform.
-
high performance poly benzoxazole benzimidazole bio based plastics with ultra low dielectric constant from 3 amino 4 Hydroxybenzoic Acid
Polymer Degradation and Stability, 2019Co-Authors: Aniruddha Nag, Mohammad Asif Ali, Kenji Takada, Makoto Watanabe, Maninder Singh, Kittima Amornwachirabodee, Shunsuke Kato, Tetsu Mitsumata, Tatsuo KanekoAbstract:Abstract High-performance bio-based plastics can make a major contribution to environmental sustainability. A series of high-performance poly(2,5-benzoxazole-co-2,5-benzimidazole)s (PBO-co-PBI) bio-based plastic films, were developed using the aromatic biomolecule 3-amino-4-Hydroxybenzoic Acid and the commercial product 3,4-diaminobenzoic Acid. The partially bio-based PBO-co-PBI films exhibit higher thermal and mechanical performance than conventional bio-based polymers such as polyamide 11 or poly(lactic Acid). The robust PBO-co-PBI films exhibit lower dielectric constants (er) than conventional high-performance aromatic polymers, attaining the value comparable to those of polyethylene or polypropylene.
-
Synthesis of thermotropic polybenzoxazole using 3-amino-4-Hydroxybenzoic Acid
Journal of Polymer Research, 2017Co-Authors: Mohammad Asif Ali, Hiroshi Shimosegawa, Aniruddha Nag, Kenji Takada, Tatsuo KanekoAbstract:Bio-based polybenzoxazoles (PBOs) are prepared by polycondensation of diAcid monomer derived from 3-amino-4-Hydroxybenzoic Acid with a series of aliphatic diamines. Resulting bio-based PBOs have high weight average molecular weight ranging 5.70–7.20 × 10^4 g/mol and show ultrahigh thermal resistance with T _ 10 values over 400 °C and T _ g values over 170 °C, which are higher than those of conventional bio-based polymers, polyamides 11 (around 60 °C) or poly(lactic Acid) (56 °C). Especially hydrazide group of the bio-based PBO were cyclized to form diazole ring by annealing at 330 °C for 20 min. The resultant PBO show liquid crystalline (LC) behavior to spin fiber in a melting state. The resultant PBO fibers showed high values of Young’s modulus and mechanical strength as compared with conventional polymers polyamide 11 and poly(lactic Acid) (PLA).
Dewa Made I Kresna - One of the best experts on this subject based on the ideXlab platform.
-
in vitro characterization of 3 chloro 4 Hydroxybenzoic Acid building block formation in ambigol biosynthesis
Organic and Biomolecular Chemistry, 2021Co-Authors: Dewa Made I Kresna, Luis Linaresotoya, Tobias M Milzarek, Elke R Duell, Masha Mir Mohseni, Ute Mettal, Gabriele M KonigAbstract:The cyanobacterium Fischerella ambigua is a natural producer of polychlorinated aromatic compounds, the ambigols A-E. The biosynthetic gene cluster (BGC) of these highly halogenated triphenyls has been recently identified by heterologous expression. It consists of 10 genes named ab1-10. Two of the encoded enzymes, i.e. Ab2 and Ab3, were identified by in vitro and in vivo assays as cytochrome P450 enzymes responsible for biaryl and biaryl ether formation. The key substrate for these P450 enzymes is 2,4-dichlorophenol, which in turn is derived from the precursor 3-chloro-4-Hydroxybenzoic Acid. Here, the biosynthetic steps leading towards 3-chloro-4-Hydroxybenzoic Acid were investigated by in vitro assays. Ab7, an isoenzyme of a 3-deoxy-7-phosphoheptulonate (DAHP) synthase, is involved in chorismate biosynthesis by the shikimate pathway. Chorismate in turn is further converted by a dedicated chorismate lyase (Ab5) yielding 4-Hydroxybenzoic Acid (4-HBA). The stand alone adenylation domain Ab6 is necessary to activate 4-HBA, which is subsequently tethered to the acyl carrier protein (ACP) Ab8. The Ab8 bound substrate is chlorinated by Ab10 in meta position yielding 3-Cl-4-HBA, which is then transfered by the condensation (C) domain to the peptidyl carrier protein and released by the thioesterase (TE) domain of Ab9. The released product is then expected to be the dedicated substrate of the halogenase Ab1 producing the monomeric ambigol building block 2,4-dichlorophenol.
