Chien Wu | NTHU - Academia.edu (original) (raw)
Papers by Chien Wu
Journal of the Chinese Chemical Society, 1993
ABSTRACT Aminopeptidase‐I from pronase contains five tryptophan residues, determined by modificat... more ABSTRACT Aminopeptidase‐I from pronase contains five tryptophan residues, determined by modification with N‐bromosuccinimide and MCD measurments. The fluorescence of the enzyme is quenched by acrylamide, a neutral quencher, but not by iodide, an anionic quencher. The quenching constant for acrylamide is about one tenth that of acctyltryptophan in aqueous solution because of the steric effect of the large protein molecule. The inaccessibility of iodide to the tryptophans is probably due to the anionic environment of the fluorophores created by the large content of Asp and Glu in the enzyme. Aminopeptidase‐I is quenched by Cu(II) and Co(II) through the formation of a nonfluorescent ground‐state complex. The results indicate that there are three accessible tryptophans for Cu(II) and two for Co(II) suggesting that some tryptophans are buried inside the enzyme and are thus inaccessible to the quencher. In the presence of a competitive inhibitor, the enzyme contains one fewer accessible tryptophan for Cu(II) indicating that this tryptophan is located in the active center. The CD spectrum of the enzyme in the far UV region is unaltered by the presence of Ca(II), whereas that in the aromatic region is enhanced significantly. The perturbation of the CD spectrum probably results from the local conformational change induced by Ca(II) or from the rigidity of the tryptophan being enhanced by the bound Ca(II).
Water research, 2004
The radiolytic degradation of methyl tert-butyl ether (MTBE) in air-equilibrated dilute solution ... more The radiolytic degradation of methyl tert-butyl ether (MTBE) in air-equilibrated dilute solution was investigated. Complete degradation of MTBE can be achieved within 5 min of irradiation at 59.7 Gy/min. The observed first-order degradation rate constant, called dose constant, increased from 0.04 to 0.56 Gy(-1) as the concentration of MTBE decreased from 92500 to 19 microg/L. Tert-butyl formate, tert-butyl alcohol, acetone and methyl acetate were found to be the primary intermediates of the degradation reaction with yields of 47%, 11%, 6.4% and 9.1%, respectively. The degradation of MTBE or its intermediates was also found to depend on the concentrations of benzene and cupric ion. The study shows that the removal of MTBE can be significantly decreased with increasing concentration of benzene. Little affects were observed with the presence of cupric ions, while the degradation of TBF was apparently reduced. These results indicate that gamma radiolysis can be a potentially effective t...
Journal of Inorganic Biochemistry, 1995
The effect of metal ions on the catalytic and thermodynamic properties of the aminopeptidase isol... more The effect of metal ions on the catalytic and thermodynamic properties of the aminopeptidase isolated from pronase has been investigated. A decrease in K M and enhanced activity were observed for most of the metal ions examined. Ca(II) exhibits the most prominent effect on enzyme activity. The observed stability constants for the enzyme-bound metal ions are in the range of 102-106 M-l, which is much smaller than that of a metalloenzyme, indicating that the metal ion is not an integral part of the enzyme. The complexation of L-leucine-p-nitroanilide and the transition metal ions causes a reduction in free substrate concentration and hence a concomitant decrease in enzyme activity. Therefore, care must be taken to account for this decrease in substrate concentration in order to obtain reliable kinetic parameters. Binding of E and S to form ES was accompanied by a decrease in Gibbs free energy, whereas a dramatic increase in the free energy was observed for the conversion of ES to ES*. Both the enthalpy and the entropy were found to be crucial in destabilizing ES*. In the presence of Ca(lI), ES is stabilized by ~ 1 kcal/mol and ES* by ~1.4 kcal/mol. The stabilization of ES by the presence of Ca(II) is reflected by a smaller KM value compared to that of the metal-free enzyme. The activation free energies for the process E + S ~ ES* were 10.8 and 9.4 kcal/mol for the metal-free and the Ca(II)-activated enzymes, respectively. The difference of ~ 1.4 kcal/mol in the activation free energy may account for enhanced activity by the presence of Ca(II).
Journal of Chromatography A, 2002
A method for the analysis of six alkyl organoiodides (iodomethane, iodoethane, 1-iodopropane, 1-i... more A method for the analysis of six alkyl organoiodides (iodomethane, iodoethane, 1-iodopropane, 1-iodobutane, 1-iodopentane, 1-iodohexane) commonly found in acetic acid process was developed. In this method the target analytes were determined by high-performance liquid chromatography (HPLC) using a post-column photochemical reactor with electrochemical detection (ED) in less than 30 min. HPLC was performed in ODS C18 reversed-phase column (5 microm, 250 x 4.6 mm I.D.) under isocratic conditions with methanol-0.067 M acetate buffer (70:30, v/v), pH 6.2 as mobile phase at flow-rate 1.1 ml/min. Alkyl organoiodides, which are electrochemically inactive, were made oxidizable at potential of 120 mV after post-column irradiation with low-pressure mercury lamp in a knitted PTFE tube. The photoreactor was placedin an aluminum housing full of nitrogen in order to prevent from the interference of oxygen. The detection limit for most analytes was of the order of 1-2 microg/l. The HPLC-ED method with a post-column photochemical reactor has good precision and linearity and can be readily applied to the routine determination of alkyl organoiodides in real acetic acid samples.
Journal of Chromatography A, 2005
This paper describes the feasibility of employing capillary electrophoresis (CE) to separate silv... more This paper describes the feasibility of employing capillary electrophoresis (CE) to separate silver particles in nanometer regimes. We have found that the addition of an anionic surfactant, sodium dodecyl sulphate (SDS), to the running electrolyte prevents coalescence of the silver particles during the process, which improves the separation performance; the concentration of SDS required for optimal silver nanoparticle separation is ca. 20 mM. By monitoring the electropherograms using a diode-array detection (DAD) system, we have also investigated the separation of suspended silver nanorods with respect to their shapes. Our results demonstrate that the combination of CE and DAD is a powerful one for the separation and characterization of various silver nanoparticles.
Journal of Chromatography A, 2009
A simple and sensitive method is described for the determination of picomolar amounts of C 1 -C 9... more A simple and sensitive method is described for the determination of picomolar amounts of C 1 -C 9 linear aliphatic aldehydes in waters containing heavy metal ions. In this method, aldehydes were first derivatized with 2,4-dinitrophenylhydrazine (DNPH) at optimized pH 1.8 for 30 min and analyzed by HPLC with UV detector at 365 nm. Factors affecting the derivatization reaction of aldehydes and DNPH were investigated. Cupric ion, an example of heavy metals, is a common oxidative reagent, which may oxidize DNPH and greatly interfere with the determination of aldehydes. EDTA was used to effectively mask the interferences by heavy metal ions. The method detection limits for direct injection of derivatized most aldehydes except formaldehyde were of the order of 7-28 nM. The detection limit can be further lowered by using off-line C 18 adsorption cartridge enrichment. The recoveries of C 1 -C 9 aldehydes were 93-115% with a relative standard deviation of 3.6-8.1% at the 0.1 M level for aldehydes. The HPLC-DNPH method has been applied for determining aldehyde photoproducts from Cu(II)-amino acid complex systems.
Journal of Chromatography A, 2003
Chromatographia, 2002
... for High-Tech Industries CHWu/JT Lu/JG Lo* ... Each new fiber was condi-tioned for 60 min at ... more ... for High-Tech Industries CHWu/JT Lu/JG Lo* ... Each new fiber was condi-tioned for 60 min at 230 ~ before use. Sample aliquots of 2.5 mL were placed in amber vials (height, 45 mm; diameter, 15 mm) and capped with 13-mm PTFE/sili-cone septa and Teflon screw caps. ...
Bioresource Technology, 2008
Carbonized moso bamboo (Phyllostachys pubescens) was coated with TiO(2) nanoparticles to enhance ... more Carbonized moso bamboo (Phyllostachys pubescens) was coated with TiO(2) nanoparticles to enhance its removal efficiency of harmful gases. Carbonized bamboo-TiO(2) composite (CBC) was prepared by heating mixtures of carbonized bamboo powder (CB) and TiO(2) nanoparticles, denoted as CBM, under nitrogen condition. TiO(2) nanoparticle and carbonized bamboo powder were mixed with the mass ratios of 1/1 and 2/1, respectively. At the same mass ratio of TiO(2) to CB, the benzene and toluene removal efficiencies follow the trend: CBC>CBM>CB, which is consistent with the amount of TiO(2) validated by elemental analysis. Sorption mechanism of benzene and toluene by CB, CBM and CBC might belong to hydrophobic-hydrophobic interaction, observed by depletion of untreated bamboo (UB) carbohydrates during carbonization. Sorption kinetics was further analyzed, and optimal correlation was found by fitting with the Elovich kinetic equation.
![Research paper thumbnail of Corrigendum to “Differential optical absorption spectrometer measurement of NO, SO, O, HCHO and aromatic volatile organics in ambient air of Kaohsiung Petroleum Refinery in Taiwan” [Atmos. Env. 39(5) (2005) 929–943]](https://attachments.academia-assets.com/64974914/thumbnails/1.jpg)
](Atmospheric Environment, 2005
Atmospheric Environment, 2004
The air quality assessment for volatile organic compounds (VOC) was conducted in and around Chine... more The air quality assessment for volatile organic compounds (VOC) was conducted in and around Chinese petroleum corporation (CPC) refinery at Kaohsiung, located in southern Taiwan, during 2001 by collecting air samples at 26 sites. Benzene and toluene were detected as the most abundant VOC by both gas chromatography and ultra-violet differential optical absorption spectroscopy (UV-DOAS) techniques. BTXE concentrations showed day and night variations at some of the sampling site. The highest among the 26 sites for total concentration of VOC at CPC was 2506 ppbv near waste burning stack. High concentrations of VOC were also detected at the wastewater management area and the east gate of the plant. The values were 10-18 times higher than those probed in Kaohsiung city. The meteorological parameters such as wind speed and direction played vital roles in the distribution of ambient air VOC concentrations and affected the petrochemical complex emissions. The application of UV-DOAS for online monitoring of criteria pollutants appears feasible though the accuracy of the technique is not fully controlled. r
Atmospheric Environment, 2005
UV-differential optical absorption spectrometer (DOAS) technique is considered as a promising tec... more UV-differential optical absorption spectrometer (DOAS) technique is considered as a promising technique to detect gaseous pollutants and was applied to conduct one-week continuous measurements in the Chinese Petroleum (CPC) refinery plant located in Lin Yuan industrial park of Kaohsiung, Southern Taiwan. With the combination of local meteorological information, including solar radiation, wind direction and speed, the results showed that the concentrations of aromatic compounds and formaldehyde (HCHO) were higher at night while the values of ozone, NO 2 and SO 2 were high during the day. The major source of aromatics was the aromatic extraction unit in the refinery while NO 2 and SO 2 were mainly emitted from chimneys with not very high average concentrations. Formaldehyde concentration was above 50 ppbv during night. There exists an apparent correlation between the variation of groundlevel ozone concentration and photochemical reactions. The results indicate that in addition to benzene and toluene, ozone is a deleterious pollutant. The commercial DOAS system provides reliable information on distribution patterns of major air pollutants depending on their concentration levels in ambient air. r
Analytica Chimica Acta, 1999
A fast and simple solvent microextraction technique using salting out-vortex-assisted liquid–liqu... more A fast and simple solvent microextraction technique using salting out-vortex-assisted liquid–liquid microextraction (salting out-VALLME) was developed for the extraction of furfurals (2-furfural (2-F), 3-furfural (3-F), 5-methylfurfural (5-MF) and 5-hydroxymethylfurfural (5-HMF)) and patulin (PAT) in fruit juice samples. The optimum extraction conditions for 5 mL sample were: extraction solvent, 1-hexanol; volume of extractant, 200 µL; vortex time, 45 s; salt addition, 20%. The simultaneous determination of the furfurals and PAT were investigated using high performance liquid chromatography coupled with diode array detector (HPLC–DAD). The separation was performed using ODS Hypersil C18 column (4.6 mm i.d×250 mm, 5 μm) under gradient elution. The detection wavelengths used for all compounds were 280 nm except for 3-F (210 nm). The furfurals and PAT were successfully separated in less than 9 min. Good linearities (r2>0.99) were obtained within the range 1–5000 μg L−1 for all compounds except for 3-F (10–5000 µg L−1) and PAT (0.5–100 μg L−1). The limits of detection (0.28–3.2 µg L−1) were estimated at S/N ratio of 3. The validated salting out-VALLME-HPLC method was applied for the analysis of furfurals and PAT in fruit juice samples (apple, mango and grape).
Fresenius Environmental Bulletin, 2006
Journal of the Chinese Chemical Society, 1993
ABSTRACT Aminopeptidase‐I from pronase contains five tryptophan residues, determined by modificat... more ABSTRACT Aminopeptidase‐I from pronase contains five tryptophan residues, determined by modification with N‐bromosuccinimide and MCD measurments. The fluorescence of the enzyme is quenched by acrylamide, a neutral quencher, but not by iodide, an anionic quencher. The quenching constant for acrylamide is about one tenth that of acctyltryptophan in aqueous solution because of the steric effect of the large protein molecule. The inaccessibility of iodide to the tryptophans is probably due to the anionic environment of the fluorophores created by the large content of Asp and Glu in the enzyme. Aminopeptidase‐I is quenched by Cu(II) and Co(II) through the formation of a nonfluorescent ground‐state complex. The results indicate that there are three accessible tryptophans for Cu(II) and two for Co(II) suggesting that some tryptophans are buried inside the enzyme and are thus inaccessible to the quencher. In the presence of a competitive inhibitor, the enzyme contains one fewer accessible tryptophan for Cu(II) indicating that this tryptophan is located in the active center. The CD spectrum of the enzyme in the far UV region is unaltered by the presence of Ca(II), whereas that in the aromatic region is enhanced significantly. The perturbation of the CD spectrum probably results from the local conformational change induced by Ca(II) or from the rigidity of the tryptophan being enhanced by the bound Ca(II).
Water research, 2004
The radiolytic degradation of methyl tert-butyl ether (MTBE) in air-equilibrated dilute solution ... more The radiolytic degradation of methyl tert-butyl ether (MTBE) in air-equilibrated dilute solution was investigated. Complete degradation of MTBE can be achieved within 5 min of irradiation at 59.7 Gy/min. The observed first-order degradation rate constant, called dose constant, increased from 0.04 to 0.56 Gy(-1) as the concentration of MTBE decreased from 92500 to 19 microg/L. Tert-butyl formate, tert-butyl alcohol, acetone and methyl acetate were found to be the primary intermediates of the degradation reaction with yields of 47%, 11%, 6.4% and 9.1%, respectively. The degradation of MTBE or its intermediates was also found to depend on the concentrations of benzene and cupric ion. The study shows that the removal of MTBE can be significantly decreased with increasing concentration of benzene. Little affects were observed with the presence of cupric ions, while the degradation of TBF was apparently reduced. These results indicate that gamma radiolysis can be a potentially effective t...
Journal of Inorganic Biochemistry, 1995
The effect of metal ions on the catalytic and thermodynamic properties of the aminopeptidase isol... more The effect of metal ions on the catalytic and thermodynamic properties of the aminopeptidase isolated from pronase has been investigated. A decrease in K M and enhanced activity were observed for most of the metal ions examined. Ca(II) exhibits the most prominent effect on enzyme activity. The observed stability constants for the enzyme-bound metal ions are in the range of 102-106 M-l, which is much smaller than that of a metalloenzyme, indicating that the metal ion is not an integral part of the enzyme. The complexation of L-leucine-p-nitroanilide and the transition metal ions causes a reduction in free substrate concentration and hence a concomitant decrease in enzyme activity. Therefore, care must be taken to account for this decrease in substrate concentration in order to obtain reliable kinetic parameters. Binding of E and S to form ES was accompanied by a decrease in Gibbs free energy, whereas a dramatic increase in the free energy was observed for the conversion of ES to ES*. Both the enthalpy and the entropy were found to be crucial in destabilizing ES*. In the presence of Ca(lI), ES is stabilized by ~ 1 kcal/mol and ES* by ~1.4 kcal/mol. The stabilization of ES by the presence of Ca(II) is reflected by a smaller KM value compared to that of the metal-free enzyme. The activation free energies for the process E + S ~ ES* were 10.8 and 9.4 kcal/mol for the metal-free and the Ca(II)-activated enzymes, respectively. The difference of ~ 1.4 kcal/mol in the activation free energy may account for enhanced activity by the presence of Ca(II).
Journal of Chromatography A, 2002
A method for the analysis of six alkyl organoiodides (iodomethane, iodoethane, 1-iodopropane, 1-i... more A method for the analysis of six alkyl organoiodides (iodomethane, iodoethane, 1-iodopropane, 1-iodobutane, 1-iodopentane, 1-iodohexane) commonly found in acetic acid process was developed. In this method the target analytes were determined by high-performance liquid chromatography (HPLC) using a post-column photochemical reactor with electrochemical detection (ED) in less than 30 min. HPLC was performed in ODS C18 reversed-phase column (5 microm, 250 x 4.6 mm I.D.) under isocratic conditions with methanol-0.067 M acetate buffer (70:30, v/v), pH 6.2 as mobile phase at flow-rate 1.1 ml/min. Alkyl organoiodides, which are electrochemically inactive, were made oxidizable at potential of 120 mV after post-column irradiation with low-pressure mercury lamp in a knitted PTFE tube. The photoreactor was placedin an aluminum housing full of nitrogen in order to prevent from the interference of oxygen. The detection limit for most analytes was of the order of 1-2 microg/l. The HPLC-ED method with a post-column photochemical reactor has good precision and linearity and can be readily applied to the routine determination of alkyl organoiodides in real acetic acid samples.
Journal of Chromatography A, 2005
This paper describes the feasibility of employing capillary electrophoresis (CE) to separate silv... more This paper describes the feasibility of employing capillary electrophoresis (CE) to separate silver particles in nanometer regimes. We have found that the addition of an anionic surfactant, sodium dodecyl sulphate (SDS), to the running electrolyte prevents coalescence of the silver particles during the process, which improves the separation performance; the concentration of SDS required for optimal silver nanoparticle separation is ca. 20 mM. By monitoring the electropherograms using a diode-array detection (DAD) system, we have also investigated the separation of suspended silver nanorods with respect to their shapes. Our results demonstrate that the combination of CE and DAD is a powerful one for the separation and characterization of various silver nanoparticles.
Journal of Chromatography A, 2009
A simple and sensitive method is described for the determination of picomolar amounts of C 1 -C 9... more A simple and sensitive method is described for the determination of picomolar amounts of C 1 -C 9 linear aliphatic aldehydes in waters containing heavy metal ions. In this method, aldehydes were first derivatized with 2,4-dinitrophenylhydrazine (DNPH) at optimized pH 1.8 for 30 min and analyzed by HPLC with UV detector at 365 nm. Factors affecting the derivatization reaction of aldehydes and DNPH were investigated. Cupric ion, an example of heavy metals, is a common oxidative reagent, which may oxidize DNPH and greatly interfere with the determination of aldehydes. EDTA was used to effectively mask the interferences by heavy metal ions. The method detection limits for direct injection of derivatized most aldehydes except formaldehyde were of the order of 7-28 nM. The detection limit can be further lowered by using off-line C 18 adsorption cartridge enrichment. The recoveries of C 1 -C 9 aldehydes were 93-115% with a relative standard deviation of 3.6-8.1% at the 0.1 M level for aldehydes. The HPLC-DNPH method has been applied for determining aldehyde photoproducts from Cu(II)-amino acid complex systems.
Journal of Chromatography A, 2003
Chromatographia, 2002
... for High-Tech Industries CHWu/JT Lu/JG Lo* ... Each new fiber was condi-tioned for 60 min at ... more ... for High-Tech Industries CHWu/JT Lu/JG Lo* ... Each new fiber was condi-tioned for 60 min at 230 ~ before use. Sample aliquots of 2.5 mL were placed in amber vials (height, 45 mm; diameter, 15 mm) and capped with 13-mm PTFE/sili-cone septa and Teflon screw caps. ...
Bioresource Technology, 2008
Carbonized moso bamboo (Phyllostachys pubescens) was coated with TiO(2) nanoparticles to enhance ... more Carbonized moso bamboo (Phyllostachys pubescens) was coated with TiO(2) nanoparticles to enhance its removal efficiency of harmful gases. Carbonized bamboo-TiO(2) composite (CBC) was prepared by heating mixtures of carbonized bamboo powder (CB) and TiO(2) nanoparticles, denoted as CBM, under nitrogen condition. TiO(2) nanoparticle and carbonized bamboo powder were mixed with the mass ratios of 1/1 and 2/1, respectively. At the same mass ratio of TiO(2) to CB, the benzene and toluene removal efficiencies follow the trend: CBC>CBM>CB, which is consistent with the amount of TiO(2) validated by elemental analysis. Sorption mechanism of benzene and toluene by CB, CBM and CBC might belong to hydrophobic-hydrophobic interaction, observed by depletion of untreated bamboo (UB) carbohydrates during carbonization. Sorption kinetics was further analyzed, and optimal correlation was found by fitting with the Elovich kinetic equation.
Atmospheric Environment, 2005
Atmospheric Environment, 2004
The air quality assessment for volatile organic compounds (VOC) was conducted in and around Chine... more The air quality assessment for volatile organic compounds (VOC) was conducted in and around Chinese petroleum corporation (CPC) refinery at Kaohsiung, located in southern Taiwan, during 2001 by collecting air samples at 26 sites. Benzene and toluene were detected as the most abundant VOC by both gas chromatography and ultra-violet differential optical absorption spectroscopy (UV-DOAS) techniques. BTXE concentrations showed day and night variations at some of the sampling site. The highest among the 26 sites for total concentration of VOC at CPC was 2506 ppbv near waste burning stack. High concentrations of VOC were also detected at the wastewater management area and the east gate of the plant. The values were 10-18 times higher than those probed in Kaohsiung city. The meteorological parameters such as wind speed and direction played vital roles in the distribution of ambient air VOC concentrations and affected the petrochemical complex emissions. The application of UV-DOAS for online monitoring of criteria pollutants appears feasible though the accuracy of the technique is not fully controlled. r
Atmospheric Environment, 2005
UV-differential optical absorption spectrometer (DOAS) technique is considered as a promising tec... more UV-differential optical absorption spectrometer (DOAS) technique is considered as a promising technique to detect gaseous pollutants and was applied to conduct one-week continuous measurements in the Chinese Petroleum (CPC) refinery plant located in Lin Yuan industrial park of Kaohsiung, Southern Taiwan. With the combination of local meteorological information, including solar radiation, wind direction and speed, the results showed that the concentrations of aromatic compounds and formaldehyde (HCHO) were higher at night while the values of ozone, NO 2 and SO 2 were high during the day. The major source of aromatics was the aromatic extraction unit in the refinery while NO 2 and SO 2 were mainly emitted from chimneys with not very high average concentrations. Formaldehyde concentration was above 50 ppbv during night. There exists an apparent correlation between the variation of groundlevel ozone concentration and photochemical reactions. The results indicate that in addition to benzene and toluene, ozone is a deleterious pollutant. The commercial DOAS system provides reliable information on distribution patterns of major air pollutants depending on their concentration levels in ambient air. r
Analytica Chimica Acta, 1999
A fast and simple solvent microextraction technique using salting out-vortex-assisted liquid–liqu... more A fast and simple solvent microextraction technique using salting out-vortex-assisted liquid–liquid microextraction (salting out-VALLME) was developed for the extraction of furfurals (2-furfural (2-F), 3-furfural (3-F), 5-methylfurfural (5-MF) and 5-hydroxymethylfurfural (5-HMF)) and patulin (PAT) in fruit juice samples. The optimum extraction conditions for 5 mL sample were: extraction solvent, 1-hexanol; volume of extractant, 200 µL; vortex time, 45 s; salt addition, 20%. The simultaneous determination of the furfurals and PAT were investigated using high performance liquid chromatography coupled with diode array detector (HPLC–DAD). The separation was performed using ODS Hypersil C18 column (4.6 mm i.d×250 mm, 5 μm) under gradient elution. The detection wavelengths used for all compounds were 280 nm except for 3-F (210 nm). The furfurals and PAT were successfully separated in less than 9 min. Good linearities (r2>0.99) were obtained within the range 1–5000 μg L−1 for all compounds except for 3-F (10–5000 µg L−1) and PAT (0.5–100 μg L−1). The limits of detection (0.28–3.2 µg L−1) were estimated at S/N ratio of 3. The validated salting out-VALLME-HPLC method was applied for the analysis of furfurals and PAT in fruit juice samples (apple, mango and grape).
Fresenius Environmental Bulletin, 2006