Biochemical and Biophysical Research Communications, Mar 1, 2007
CueO protein is a hypothetical bacterial laccase and a good laccase candidate for large scale ind... more CueO protein is a hypothetical bacterial laccase and a good laccase candidate for large scale industrial application. Four CueO crystal structures were determined at different copper concentrations. Low copper occupancy in apo-CueO and slow copper reconstitution process in CueO with exogenous copper were demonstrated. These observations well explain the copper dependence of CueO oxidase activity. Structural comparison between CueO and other three fungal laccase proteins indicates that Glu106 in CueO constitutes the primary counter-work for reconstitution of the trinuclear copper site. Mutation of Glu106 to a Phe enhanced CueO oxidation activity and supported this hypothesis. In addition, an extra a-helix from Leu351 to Gly378 covers substrate biding pocket of CueO and might compromises the electron transfer from substrate to type I copper.
Journal of Surfactants and Detergents, Oct 21, 2018
In this work, ester sulfoxide (ESO) surfactants based on 2‐hydroxy‐4‐(methylthio) butyric acid ar... more In this work, ester sulfoxide (ESO) surfactants based on 2‐hydroxy‐4‐(methylthio) butyric acid are shown to have temperature‐sensitive microemulsion phase behaviors. Both C10 (C10ESO) and C12 (C12ESO) surfactants studied contained one sulfoxide unit in the structure. Phase inversion temperatures (PIT) and interfacial tensions (IFT) between water‐rich and oil‐rich phases have been measured for ternary systems of water, oil, and sulfoxide surfactants. Hydrophilic–lipophilic deviation (HLD) parameters of these surfactants were obtained by fitting the experimental data to a semiempirical HLD equation. The characteristic surfactant parameter and temperature sensitivity of C10ESO and C12ESO surfactants were obtained and compared with similar ethoxylated alcohol surfactants. By comparing the characteristic parameters of these surfactants with those of ethoxylated alcohol surfactants, it was shown that one sulfoxide ester moiety is equally hydrophilic as approximately 5 ethylene oxide groups. The temperature sensitivity of the ESO was roughly a factor of four less than ethoxylated surfactants based on the temperature coefficient of the HLD equation.
Journal of Surfactants and Detergents, Dec 30, 2016
This manuscript describes the study of a novel sulfoxide-based surfactant class, namely the parti... more This manuscript describes the study of a novel sulfoxide-based surfactant class, namely the partially oxidized 2-hydroxy-4-(methylthio) butyrate esters. The acid group was reacted with a primary alkyl alcohol or alkyl amine to form esters or amides, respectively, and the sulfide was partially oxidized to the sulfoxide. These sulfoxide surfactants behave as non-ionic surfactants in response to electrolytes, and have very good water solubility with high cloud temperatures. Surface tensions at the critical micelle concentration as low as 30 mN/m were measured. These surfactants were synergistic with anionic surfactants in the mixed micelle and adsorbed surface monolayer. They exhibited fast surface tension decay, good wetting and foaming performance, and performed equally well as a nonyl-phenol ethoxylate surfactant in an enzyme-containing laundry formulation.
Journal of Surfactants and Detergents, Jul 9, 2015
2‐Hydroxy‐4‐(methylthio)butanoic acid (HMTBA) is a commonly used animal feed additive available i... more 2‐Hydroxy‐4‐(methylthio)butanoic acid (HMTBA) is a commonly used animal feed additive available in large quantities. In this study, anionic surfactants were synthesized utilizing HMTBA as a starting material. Specifically, a straight‐chain fatty acid containing 12 or 16 carbon atoms was attached to the hydroxyl group via esterification. After neutralization of the carboxylic acid with sodium, the molecules behave as anionic surfactants. Oxidation of the sulfur atom can be performed to further increase water solubility. The molecules exhibit critical micelle concentrations (CMCs), and lower the surface tension to 35–45 mN/m at the CMC. The derivatives have low Krafft points (<4 °C) and good wetting performance. The hardness tolerance of the ester made from dodecanoic acid is ∼2.5–4 orders of magnitude higher than an analogous carboxylate surfactant, namely sodium dodecanoate. Foam created according to the Ross‐Miles foam test is substantial, but dissipates quickly as compared to other anionic surfactants.
Processing of light tight oils (LTOs) and their blends is challenged with their high fouling prop... more Processing of light tight oils (LTOs) and their blends is challenged with their high fouling propensity. In this study, their fouling potential was attributed to fractions from centrifuge-accelerat...
Processing of light tight oils (LTOs) and their blends is challenged with their high fouling prop... more Processing of light tight oils (LTOs) and their blends is challenged with their high fouling propensity. In this study, their fouling potential was attributed to fractions from centrifuge-accelerat...
The Karamay oil sand in Xinjiang province, northwest China, forms a large heavy oil reserve. At 8... more The Karamay oil sand in Xinjiang province, northwest China, forms a large heavy oil reserve. At 8 present, a lack of understanding of the wettability of the oil sands precludes the engineers from properly 9 characterizing the efficiency of fluid injection in either water or steam-flood practices. In this study, a series of 10 experiments were conducted on a specime obtained from a Karamay oil sand reservoir, including contact angle 11 tests, scanning electron microscopy (SEM) observations, nuclear magnetic resonance (NMR) tests and zeta-12 potential tests. On the basis of the experimental results, the wettability of the Karamay oil sand as well as the 13 influences of the differential pressure and the pH on its wettability were analyzed in detail. It was found that 14 there exists a water film on the oil sand grains, implying the oil sand is water-wet. In addition, the presence and 15 stability of the water film were analyzed using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Under 16 the reservoir conditions, a water film with a thickness of 2-7 nm forms in the Karamay oil sand. Either 17 increasing the injection pressure difference or enhancing the alkaline environment during water injection will 18 contribute to the formation of a stable water film. 19
Dispersant systems for oceanic oil spill remediation have gained renewed attention following the ... more Dispersant systems for oceanic oil spill remediation have gained renewed attention following the Deepwater Horizon oil spill in 2010. The combination of surfactants and silica or clay nanoparticles and microparticles can provide synergy in the formation and stabilization of dodecane droplets in synthetic seawater. The surfactants lower the oil/water interfacial tension and allows the formation of oil/water emulsions composed of small oil drops (<100 micron diameter), while the presence of nanoparticles at the oil/water interface enhances emulsion stability by providing a larger steric barrier to droplet coalescence than surfactants alone. The use of particles may therefore reduce the concentration of surfactants required for the dispersion of oil in seawater. Droplet sizes were analyzed with optical microscopy and static light scattering, and the dispersion mechanisms for various formulations were explored via a small-scale jet apparatus. The generation of droplets via jet breaku...
Industrial & Engineering Chemistry Research, 2014
During deep sea oil leaks, dispersants may be used to break up the oil into droplets smaller than... more During deep sea oil leaks, dispersants may be used to break up the oil into droplets smaller than about 70 µm, which may then be bioremediated by bacteria before they reach the ocean surface. To investigate the mechanism of droplet formation, a flowing oleophilic stream containing amphiphiles was mixed with flowing dodecane and then atomized through a 0.25 mm circular nozzle as a function of dispersant type, concentration and jet velocity. The minimum droplet diameters were 2.2, 4.5, and 24 µm for only 5 w:v % amphiphile in the oil phase for Corexit 9500A, Tergitol 15-S-7 (C 12 H 25 CH(OCH 2 CH 2) 7 OH) and a silica nanoparticle/Span 20 mixture, respectively. For Tergitol 15-S-7, the droplet size exhibited the expected scaling with Weber number (We) at low viscosity numbers (Vi <50) where inertial forces overcome interfacial forces, and Reynolds number (Re) at high Vi numbers (Vi>50), where inertial forces overcome viscous forces. However, in the case of the silica nanoparticle/Span 20 mixture, the magnitude of the exponent of We scaling was found to be smaller than-3/5. A better understanding of how low concentrations of dispersants (with relatively high Page 1 of 36 ACS Paragon Plus Environment Industrial & Engineering Chemistry Research oil/water interfacial tensions) may be used to provide a sufficient We with high inertial forces (high Re) in jets to form small oil droplets is of interest for advancing environmental protection in the undesired event of a deep sea oil leak.
A lead salt mid-infrared laser sample grown by molecular-beam epitaxy (MBE) on a polished BaF2 (1... more A lead salt mid-infrared laser sample grown by molecular-beam epitaxy (MBE) on a polished BaF2 (110) substrate is studied. For improving the laser performance at higher operating temperature, a method of substrate transfer from a BaF2 substrate to a copper heat sink is developed. The cleaved facet along the {100} plane, which is helpful for the formation of a Fabry-Pérot
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
ABSTRACT Asphaltenes from six different crude oils were isolated and tested with respect to their... more ABSTRACT Asphaltenes from six different crude oils were isolated and tested with respect to their water solubility and interfacial behavior at temperatures as high as 190 °C and 125 °C respectively in (1) water with 18 MΩ*cm resistance, (2) a 8 wt.% NaCl-2 wt.% CaCl2 salt solution, and (3) artificial seawater. None of the asphaltenes had any water solubility except for possibly very slight solubility in two cases. A higher interfacial activity was found to be loosely correlated with asphaltene molecular weight as measured by freezing point depression measurements; a lower molecular weight asphaltene had a higher interfacial activity. Chemical measurements of the asphaltenes were performed and only hydrogen content appeared to possibly correlate with interfacial activity; the interfacial activity decreased as the hydrogen content increased. Overall, the interfacial activity was highest for artificial seawater, and lowest for pure water and brine. Interfacial tensions (IFTs) were also measured from room temperature to 125 °C at a fixed concentration of 5 g/l in toluene for the artificial seawater and pure water. With a couple of exceptions, decreases of IFT with temperature were very similar for all asphaltenes and smaller than that of the pure water/toluene system. Higher temperature did lead to a slightly larger decrease of IFT at long times where rearrangement of the interfacial layer has been postulated to occur.
Biochemical and Biophysical Research Communications, 2007
CueO protein is a hypothetical bacterial laccase and a good laccase candidate for large scale ind... more CueO protein is a hypothetical bacterial laccase and a good laccase candidate for large scale industrial application. Four CueO crystal structures were determined at different copper concentrations. Low copper occupancy in apo-CueO and slow copper reconstitution process in CueO with exogenous copper were demonstrated. These observations well explain the copper dependence of CueO oxidase activity. Structural comparison between CueO and other three fungal laccase proteins indicates that Glu106 in CueO constitutes the primary counter-work for reconstitution of the trinuclear copper site. Mutation of Glu106 to a Phe enhanced CueO oxidation activity and supported this hypothesis. In addition, an extra a-helix from Leu351 to Gly378 covers substrate biding pocket of CueO and might compromises the electron transfer from substrate to type I copper.
A high-quality as-grown PbSe film with a record low threading dislocation density of 9×105 cm−2 o... more A high-quality as-grown PbSe film with a record low threading dislocation density of 9×105 cm−2 on patterned Si(111) substrate has been obtained using molecular beam epitaxy. The mechanisms leading to the remarkable reduction in threading dislocation density are analyzed. Based on the analysis, further reduction in dislocation density is anticipated. Materials with such low dislocation density should significantly improve the Si-based IV-VI group device performance.
Biochemical and Biophysical Research Communications, Mar 1, 2007
CueO protein is a hypothetical bacterial laccase and a good laccase candidate for large scale ind... more CueO protein is a hypothetical bacterial laccase and a good laccase candidate for large scale industrial application. Four CueO crystal structures were determined at different copper concentrations. Low copper occupancy in apo-CueO and slow copper reconstitution process in CueO with exogenous copper were demonstrated. These observations well explain the copper dependence of CueO oxidase activity. Structural comparison between CueO and other three fungal laccase proteins indicates that Glu106 in CueO constitutes the primary counter-work for reconstitution of the trinuclear copper site. Mutation of Glu106 to a Phe enhanced CueO oxidation activity and supported this hypothesis. In addition, an extra a-helix from Leu351 to Gly378 covers substrate biding pocket of CueO and might compromises the electron transfer from substrate to type I copper.
Journal of Surfactants and Detergents, Oct 21, 2018
In this work, ester sulfoxide (ESO) surfactants based on 2‐hydroxy‐4‐(methylthio) butyric acid ar... more In this work, ester sulfoxide (ESO) surfactants based on 2‐hydroxy‐4‐(methylthio) butyric acid are shown to have temperature‐sensitive microemulsion phase behaviors. Both C10 (C10ESO) and C12 (C12ESO) surfactants studied contained one sulfoxide unit in the structure. Phase inversion temperatures (PIT) and interfacial tensions (IFT) between water‐rich and oil‐rich phases have been measured for ternary systems of water, oil, and sulfoxide surfactants. Hydrophilic–lipophilic deviation (HLD) parameters of these surfactants were obtained by fitting the experimental data to a semiempirical HLD equation. The characteristic surfactant parameter and temperature sensitivity of C10ESO and C12ESO surfactants were obtained and compared with similar ethoxylated alcohol surfactants. By comparing the characteristic parameters of these surfactants with those of ethoxylated alcohol surfactants, it was shown that one sulfoxide ester moiety is equally hydrophilic as approximately 5 ethylene oxide groups. The temperature sensitivity of the ESO was roughly a factor of four less than ethoxylated surfactants based on the temperature coefficient of the HLD equation.
Journal of Surfactants and Detergents, Dec 30, 2016
This manuscript describes the study of a novel sulfoxide-based surfactant class, namely the parti... more This manuscript describes the study of a novel sulfoxide-based surfactant class, namely the partially oxidized 2-hydroxy-4-(methylthio) butyrate esters. The acid group was reacted with a primary alkyl alcohol or alkyl amine to form esters or amides, respectively, and the sulfide was partially oxidized to the sulfoxide. These sulfoxide surfactants behave as non-ionic surfactants in response to electrolytes, and have very good water solubility with high cloud temperatures. Surface tensions at the critical micelle concentration as low as 30 mN/m were measured. These surfactants were synergistic with anionic surfactants in the mixed micelle and adsorbed surface monolayer. They exhibited fast surface tension decay, good wetting and foaming performance, and performed equally well as a nonyl-phenol ethoxylate surfactant in an enzyme-containing laundry formulation.
Journal of Surfactants and Detergents, Jul 9, 2015
2‐Hydroxy‐4‐(methylthio)butanoic acid (HMTBA) is a commonly used animal feed additive available i... more 2‐Hydroxy‐4‐(methylthio)butanoic acid (HMTBA) is a commonly used animal feed additive available in large quantities. In this study, anionic surfactants were synthesized utilizing HMTBA as a starting material. Specifically, a straight‐chain fatty acid containing 12 or 16 carbon atoms was attached to the hydroxyl group via esterification. After neutralization of the carboxylic acid with sodium, the molecules behave as anionic surfactants. Oxidation of the sulfur atom can be performed to further increase water solubility. The molecules exhibit critical micelle concentrations (CMCs), and lower the surface tension to 35–45 mN/m at the CMC. The derivatives have low Krafft points (&lt;4 °C) and good wetting performance. The hardness tolerance of the ester made from dodecanoic acid is ∼2.5–4 orders of magnitude higher than an analogous carboxylate surfactant, namely sodium dodecanoate. Foam created according to the Ross‐Miles foam test is substantial, but dissipates quickly as compared to other anionic surfactants.
Processing of light tight oils (LTOs) and their blends is challenged with their high fouling prop... more Processing of light tight oils (LTOs) and their blends is challenged with their high fouling propensity. In this study, their fouling potential was attributed to fractions from centrifuge-accelerat...
Processing of light tight oils (LTOs) and their blends is challenged with their high fouling prop... more Processing of light tight oils (LTOs) and their blends is challenged with their high fouling propensity. In this study, their fouling potential was attributed to fractions from centrifuge-accelerat...
The Karamay oil sand in Xinjiang province, northwest China, forms a large heavy oil reserve. At 8... more The Karamay oil sand in Xinjiang province, northwest China, forms a large heavy oil reserve. At 8 present, a lack of understanding of the wettability of the oil sands precludes the engineers from properly 9 characterizing the efficiency of fluid injection in either water or steam-flood practices. In this study, a series of 10 experiments were conducted on a specime obtained from a Karamay oil sand reservoir, including contact angle 11 tests, scanning electron microscopy (SEM) observations, nuclear magnetic resonance (NMR) tests and zeta-12 potential tests. On the basis of the experimental results, the wettability of the Karamay oil sand as well as the 13 influences of the differential pressure and the pH on its wettability were analyzed in detail. It was found that 14 there exists a water film on the oil sand grains, implying the oil sand is water-wet. In addition, the presence and 15 stability of the water film were analyzed using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Under 16 the reservoir conditions, a water film with a thickness of 2-7 nm forms in the Karamay oil sand. Either 17 increasing the injection pressure difference or enhancing the alkaline environment during water injection will 18 contribute to the formation of a stable water film. 19
Dispersant systems for oceanic oil spill remediation have gained renewed attention following the ... more Dispersant systems for oceanic oil spill remediation have gained renewed attention following the Deepwater Horizon oil spill in 2010. The combination of surfactants and silica or clay nanoparticles and microparticles can provide synergy in the formation and stabilization of dodecane droplets in synthetic seawater. The surfactants lower the oil/water interfacial tension and allows the formation of oil/water emulsions composed of small oil drops (<100 micron diameter), while the presence of nanoparticles at the oil/water interface enhances emulsion stability by providing a larger steric barrier to droplet coalescence than surfactants alone. The use of particles may therefore reduce the concentration of surfactants required for the dispersion of oil in seawater. Droplet sizes were analyzed with optical microscopy and static light scattering, and the dispersion mechanisms for various formulations were explored via a small-scale jet apparatus. The generation of droplets via jet breaku...
Industrial & Engineering Chemistry Research, 2014
During deep sea oil leaks, dispersants may be used to break up the oil into droplets smaller than... more During deep sea oil leaks, dispersants may be used to break up the oil into droplets smaller than about 70 µm, which may then be bioremediated by bacteria before they reach the ocean surface. To investigate the mechanism of droplet formation, a flowing oleophilic stream containing amphiphiles was mixed with flowing dodecane and then atomized through a 0.25 mm circular nozzle as a function of dispersant type, concentration and jet velocity. The minimum droplet diameters were 2.2, 4.5, and 24 µm for only 5 w:v % amphiphile in the oil phase for Corexit 9500A, Tergitol 15-S-7 (C 12 H 25 CH(OCH 2 CH 2) 7 OH) and a silica nanoparticle/Span 20 mixture, respectively. For Tergitol 15-S-7, the droplet size exhibited the expected scaling with Weber number (We) at low viscosity numbers (Vi <50) where inertial forces overcome interfacial forces, and Reynolds number (Re) at high Vi numbers (Vi>50), where inertial forces overcome viscous forces. However, in the case of the silica nanoparticle/Span 20 mixture, the magnitude of the exponent of We scaling was found to be smaller than-3/5. A better understanding of how low concentrations of dispersants (with relatively high Page 1 of 36 ACS Paragon Plus Environment Industrial & Engineering Chemistry Research oil/water interfacial tensions) may be used to provide a sufficient We with high inertial forces (high Re) in jets to form small oil droplets is of interest for advancing environmental protection in the undesired event of a deep sea oil leak.
A lead salt mid-infrared laser sample grown by molecular-beam epitaxy (MBE) on a polished BaF2 (1... more A lead salt mid-infrared laser sample grown by molecular-beam epitaxy (MBE) on a polished BaF2 (110) substrate is studied. For improving the laser performance at higher operating temperature, a method of substrate transfer from a BaF2 substrate to a copper heat sink is developed. The cleaved facet along the {100} plane, which is helpful for the formation of a Fabry-Pérot
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
ABSTRACT Asphaltenes from six different crude oils were isolated and tested with respect to their... more ABSTRACT Asphaltenes from six different crude oils were isolated and tested with respect to their water solubility and interfacial behavior at temperatures as high as 190 °C and 125 °C respectively in (1) water with 18 MΩ*cm resistance, (2) a 8 wt.% NaCl-2 wt.% CaCl2 salt solution, and (3) artificial seawater. None of the asphaltenes had any water solubility except for possibly very slight solubility in two cases. A higher interfacial activity was found to be loosely correlated with asphaltene molecular weight as measured by freezing point depression measurements; a lower molecular weight asphaltene had a higher interfacial activity. Chemical measurements of the asphaltenes were performed and only hydrogen content appeared to possibly correlate with interfacial activity; the interfacial activity decreased as the hydrogen content increased. Overall, the interfacial activity was highest for artificial seawater, and lowest for pure water and brine. Interfacial tensions (IFTs) were also measured from room temperature to 125 °C at a fixed concentration of 5 g/l in toluene for the artificial seawater and pure water. With a couple of exceptions, decreases of IFT with temperature were very similar for all asphaltenes and smaller than that of the pure water/toluene system. Higher temperature did lead to a slightly larger decrease of IFT at long times where rearrangement of the interfacial layer has been postulated to occur.
Biochemical and Biophysical Research Communications, 2007
CueO protein is a hypothetical bacterial laccase and a good laccase candidate for large scale ind... more CueO protein is a hypothetical bacterial laccase and a good laccase candidate for large scale industrial application. Four CueO crystal structures were determined at different copper concentrations. Low copper occupancy in apo-CueO and slow copper reconstitution process in CueO with exogenous copper were demonstrated. These observations well explain the copper dependence of CueO oxidase activity. Structural comparison between CueO and other three fungal laccase proteins indicates that Glu106 in CueO constitutes the primary counter-work for reconstitution of the trinuclear copper site. Mutation of Glu106 to a Phe enhanced CueO oxidation activity and supported this hypothesis. In addition, an extra a-helix from Leu351 to Gly378 covers substrate biding pocket of CueO and might compromises the electron transfer from substrate to type I copper.
A high-quality as-grown PbSe film with a record low threading dislocation density of 9×105 cm−2 o... more A high-quality as-grown PbSe film with a record low threading dislocation density of 9×105 cm−2 on patterned Si(111) substrate has been obtained using molecular beam epitaxy. The mechanisms leading to the remarkable reduction in threading dislocation density are analyzed. Based on the analysis, further reduction in dislocation density is anticipated. Materials with such low dislocation density should significantly improve the Si-based IV-VI group device performance.
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