The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform
Jin-xin Xiao - One of the best experts on this subject based on the ideXlab platform.
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Effect of anionic surfactant molecular structure on bovine serum albumin (BSA) fluorescence
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006Co-Authors: Aoneng Cao, Luhua Lai, Jin-xin XiaoAbstract:Abstract The interactions of BSA with different anionic surfactants, such as sodium Alkyl sulfate (CnSO4Na, n = 8, 10 and 12), sodium Alkyl Sulfonate (CnSO3Na, n = 8, 10 and 12) and sodium Alkyl carboxylate (CnCOONa, n = 9 and 11) were investigated by fluorescence spectroscopy. The effect of molecular structure of anionic surfactants, such as the types of hydrophilic groups and the lengths of hydrophobic chain, on BSA intrinsic fluorescence was examined. It was shown that addition of anionic surfactants induced strong quenching of BSA fluorescence. The quenching of BSA fluorescence relied on the hydrophobic chain lengths of surfactant. The more hydrophobic surfactant had a greater capacity to quench BSA fluorescence. However, anionic surfactants with different headgroups did not show significant difference, e.g., CnSO4− and CnSO3− with same Alkyl chain had similar quenching effect on BSA fluorescence.
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Surfactant-induced refolding of lysozyme
Biochimica et biophysica acta, 2005Co-Authors: Jin-xin Xiao, Aoneng Cao, Luhua Lai, Bu-yao Zhu, Guo-xi ZhaoAbstract:Abstract The surfactant–lysozyme interaction was investigated by circular dichroism, fluorescence, UV, dynamic light scattering, surface tension, turbidity measurements and lysozyme activity assay. A new way of refolding of lysozyme was found. It was shown that the lysozyme unfolded by anionic surfactants could be renatured by adding cationic surfactants. That is, lysozyme formed precipitate with anionic surfactants, the precipitates could be dissolved by adding a cationic surfactant solution, and then the lysozyme was refolded to its native state spontaneously. Different couples of anionic surfactants and cationic surfactants including C10SO3/C10NE, C12SO3/C10NE, C10SO3/C12NE, C10SO3/C12NB, C10SO4/C10NE and C12SO4/C10NE (CnSO3, CnSO4, CnNE and CnNB represent sodium Alkyl Sulfonate/sulfate, Alkyl triethyl/butyl ammonium bromide respectively) were investigated, all of them gave similar results. The results were explained in terms of the differences between the interaction of anionic–cationic surfactants and that of surfactant–lysozyme. It was thought that the formation of mixed micelles of anionic–cationic surfactants is a more favorable process than that of lysozyme–surfactant complexes, which induces the dissociation of lysozyme–surfactant complexes when cationic surfactants were added.
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polymer surfactant interaction differences between Alkyl sulfate and Alkyl Sulfonate
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004Co-Authors: Peng Yan, Jin-xin XiaoAbstract:Abstract The interactions between sodium Alkyl sulfates (CnSO4)/sodium Alkyl Sulfonates (CnSO3) and polyethylene oxide (PEO) were studied by surface tension, fluorescence and dynamic light scattering measurements, assisted with quantum-chemical calculations. It was found that, although many properties of CnSO4 and CnSO3 were similar, there were striking differences in their interactions with PEO. Sodium Alkyl Sulfonates were seen to interact more weakly than their sulfate analogs. Such differences were especially distinct when compared C10SO4-PEO with C10SO3-PEO, the former exhibits obvious interactions, but no observable interaction in the latter. With the help of ab initio quantum-chemical calculation, the results were explained.
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Polymer–surfactant interaction: differences between Alkyl sulfate and Alkyl Sulfonate
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004Co-Authors: Peng Yan, Jin-xin XiaoAbstract:Abstract The interactions between sodium Alkyl sulfates (CnSO4)/sodium Alkyl Sulfonates (CnSO3) and polyethylene oxide (PEO) were studied by surface tension, fluorescence and dynamic light scattering measurements, assisted with quantum-chemical calculations. It was found that, although many properties of CnSO4 and CnSO3 were similar, there were striking differences in their interactions with PEO. Sodium Alkyl Sulfonates were seen to interact more weakly than their sulfate analogs. Such differences were especially distinct when compared C10SO4-PEO with C10SO3-PEO, the former exhibits obvious interactions, but no observable interaction in the latter. With the help of ab initio quantum-chemical calculation, the results were explained.
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Striking differences between Alkyl sulfate and Alkyl Sulfonate when mixed with cationic surfactants
Colloid & Polymer Science, 2004Co-Authors: Li Chen, Jin-xin XiaoAbstract:The properties of Alkyl sulfate and Alkyl Sulfonate are similar except for their Krafft points. However, Alkyl sulfate and Alkyl Sulfonate behave quite differently when they are mixed with cationic surfactants and show some totally unexpected results. In this work sodium Alkyl sulfate (CnH2n+1SO4Na,CnSO4)–Alkyl quaternary ammonium bromide [CnH2n+1N(CmH2m+1)3Br, CnN, m=1–4] mixtures and sodium Alkyl Sulfonate (CnH2n+1SO3Na, CnSO3)–CnN mixtures were studied. It was found that, in contrast to the single surfactants, CnSO3–CnN mixtures were much more soluble than CnSO4–CnN mixtures. Besides, the two kinds of catanionic surfactant mixtures were quite different in their phase behavior and aggregate properties. The results were interpreted in terms of the interactions between surfactant molecules, which were very different in the two kinds of mixed systems owing to the distinction between Alkyl sulfate and Alkyl Sulfonate in the molecular charge distribution.
Aram A. Shahinyan - One of the best experts on this subject based on the ideXlab platform.
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Shape of Long Chain Alkyl Sulfonate Micelle upon Salt Addition: a Molecular Dynamics Study
Journal of Surfactants and Detergents, 2015Co-Authors: Armen H. Poghosyan, Levon H. Arsenyan, Aram A. ShahinyanAbstract:Here we report a molecular dynamics simulation on the state of long chain Alkyl Sulfonate micelle which occurs in the presence of salt. We tracked the formation of a large micelle with a dumbbell-like shape, which has hemispherical end caps with a large radius rather than the middle cylindrical body, where the shape bending angle was around 160^o. The data from chain analysis indicate that the micelle hydrocarbon layer is covered with disordered tails. We also report micelle fission controlled by changes in salt concentration. Overall, the parameters obtained are compared with existing experimental findings.
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Long-chain Alkyl Sulfonate micelle fission: a molecular dynamics study
Colloid and Polymer Science, 2014Co-Authors: Armen H. Poghosyan, Levon H. Arsenyan, Aram A. ShahinyanAbstract:In this study, we investigate micelle fission of long-chain Alkyl Sulfonate molecules using atomistic scale simulation. GROMACS software code with the united atom force field was applied. 0.5-μs parallel molecular dynamics simulation study was conducted for a surfactant/water system consisting of 192 sodium pentadecyl Sulfonate and 40,553 water molecules. The large preassembled micelle was ruptured at Krafft above T = 323-K temperature, and we track two ellipsoid-like micelles over the course of the production run. To estimate the micelle shape, we determined the principal moments of inertia and the eccentricity, which proved that the micelles have a pronounced prolate spheroid shape, which agrees well with our previous experimental data. The mechanism of micelle fission was explored in detail. The aggregation number, ionization degree, and other parameters obtained from simulation were consistent with existing experimental finding. The determined parameters in addition to simple visual inspection of trajectories revealed monomer-micelle exchange—with the estimated relaxation time τ _1 = 10^− 9s. We assume that the exchange process is conditioned by the unequal size of micelles leading to adjustment of aggregation number.
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atomic level and coarse grained simulation of long chain Alkyl Sulfonate micelle self assembly
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014Co-Authors: Armen H. Poghosyan, Levon H. Arsenyan, L A Antonyan, Aram A. ShahinyanAbstract:Abstract A series of long runs were performed on pentadecyl Sulfonate/water systems using both atomic level and coarse-grained approaches. Surfactant micelle fusion was observed with coarse-grained approach; however, the atomic scale study did not reach the equilibrium even at long timescales. The shape of micellar aggregate appeared as to be prolate spheroidal rather than spherical. The aggregation number, hydrocarbon tails and water properties were also examined. The comparison data obtained from atomic level and coarse-grained are in agreement with previous reports. In this report self-assembly of micelle formation is discussed. We state that the growth of micelles occurs by gradually coalescence of micellar aggregates. We suggest that with coarse-grained approach equilibrium is achieved at dispersed initial configuration and therefore, the model is ideally suited to describe the dynamical nature of the self-assembly of surfactants.
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molecular dynamics study of intermediate phase of long chain Alkyl Sulfonate water systems
Langmuir, 2013Co-Authors: Armen H. Poghosyan, Levon H. Arsenyan, Aram A. ShahinyanAbstract:Using atomic level simulation we aimed to investigate various intermediate phases of the long chain Alkyl Sulfonate/water system. Overall, about 800 ns parallel molecular dynamics simulation study was conducted for a surfactant/water system consisting of 128 sodium pentadecyl Sulfonate and 2251 water molecules. The GROMACS software code with united atom force field was applied. Despite some differences, the analysis of main structural parameters is in agreement with X-ray experimental findings. The mechanism of self-assembly of SPDS molecules was also examined. At T = 323 K we obtained both tilted fully interdigitated and liquid crystalline-like disordered hydrocarbon chains; hence, the presence of either gel phase that coexists with a lamellar phase or metastable gel phase with fraction of gauche configuration can be assumed. Further increase of temperature revealed that the system underwent a transition to a lamellar phase, which was clearly identified by the presence of fully disordered hydrocarbon cha...
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Molecular dynamics study of intermediate phase of long chain Alkyl Sulfonate/water systems.
Langmuir : the ACS journal of surfaces and colloids, 2012Co-Authors: Armen H. Poghosyan, Levon H. Arsenyan, Aram A. ShahinyanAbstract:Using atomic level simulation we aimed to investigate various intermediate phases of the long chain Alkyl Sulfonate/water system. Overall, about 800 ns parallel molecular dynamics simulation study was conducted for a surfactant/water system consisting of 128 sodium pentadecyl Sulfonate and 2251 water molecules. The GROMACS software code with united atom force field was applied. Despite some differences, the analysis of main structural parameters is in agreement with X-ray experimental findings. The mechanism of self-assembly of SPDS molecules was also examined. At T = 323 K we obtained both tilted fully interdigitated and liquid crystalline-like disordered hydrocarbon chains; hence, the presence of either gel phase that coexists with a lamellar phase or metastable gel phase with fraction of gauche configuration can be assumed. Further increase of temperature revealed that the system underwent a transition to a lamellar phase, which was clearly identified by the presence of fully disordered hydrocarbon cha...
David J. Snodin - One of the best experts on this subject based on the ideXlab platform.
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Elusive Impurities—Evidence versus Hypothesis. Technical and Regulatory Update on Alkyl Sulfonates in Sulfonic Acid Salts
Organic Process Research & Development, 2019Co-Authors: David J. SnodinAbstract:There is a widespread and long-standing perception that drug substances presented as sulfonic acid salts pose an inherent risk to patients, owing to the potential presence of mutagenic Alkyl Sulfonate impurities. Extensive and indisputable kinetic, mechanistic, and experimental evidence indicates that this is not a sustainable position. Sulfonic acid salt formation normally involves addition of a sulfonic acid to an equimolar amount of the base form of a drug substance dissolved in a suitable solvent (most frequently ethanol or other protic solvent). In such systems, no Alkyl Sulfonate impurities are generated via an ester-forming side reaction, owing to essentially instantaneous base protonation and neutralization of the acidic component. Carryover of impurities in sulfonic acids is considered highly unlikely, given the use of pharma-grade reagents and the significant in-built purge factors based on dilution and the high solubility of Alkyl Sulfonates in alcohol solvents. Efforts to create a dialogue wit...
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Mutagenic Alkyl-Sulfonate Impurities in Sulfonic Acid Salts: Reviewing the Evidence and Challenging Regulatory Perceptions
Organic Process Research & Development, 2015Co-Authors: David J. Snodin, Andrew TeasdaleAbstract:Alkyl Sulfonates are direct-acting bacterial mutagens and are almost universally regarded by regulatory authorities to be potential impurities in drug substances presented as sulfonic acid salts, particularly if synthesized using an alcohol solvent. A detailed review of the available public domain data indicates that regulatory policy appears to be based on speculation, assumption, and assertion rather than actual evidence. Ester formation from a sulfonic acid in the presence of an alcohol is an extremely slow and thermodynamically unfavored reaction requiring strongly acidic conditions to produce even minimal conversion. Following addition of an equimolar amount of a sulfonic acid to a pharmaceutical base (the active), proton transfer to form an acid salt occurs instantaneously, thus neutralizing the acid and precluding any ester formation as a side reaction even if an alcoholic solvent is employed. Other possible routes to sulfonic acid ester formation by interaction of an alcohol with preformed sulfoni...
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Drug substances presented as sulfonic acid salts: overview of utility, safety and regulation.
The Journal of pharmacy and pharmacology, 2009Co-Authors: David P. Elder, David J. SnodinAbstract:Objectives Controlling genotoxic impurities represents a significant challenge to both industry and regulators. The potential for formation of genotoxic short-chain Alkyl esters of sulfonic acids during synthesis of sulfonic acid salts is a long-standing regulatory concern. This review provides a general overview of the utility of sulfonic acids as salt-forming moieties and discusses strategies for effectively minimizing the potential for Alkyl Sulfonate formation during the synthesis and processing of Sulfonate salt active pharmaceutical ingredients. The potential implications of the recent establishment of a substantial human threshold dose for ethyl methaneSulfonate for the safety assessment of Alkyl Sulfonates in general are also discussed. Key findings The formation of Alkyl Sulfonates requires highly acidic conditions, possibly combined with long reaction times and/or elevated temperatures, to generate significant amounts, and these conditions are most unlikely to be present in the synthesis of active pharmaceutical ingredient Sulfonate salts. It is possible to design salt formation conditions, using a short-chain alcohol as solvent, to manufacture Sulfonate salts that are essentially free of Alkyl Sulfonate impurities. Processes using non-acidic conditions such as ethanol recrystallization or wet granulation should not raise any concerns of Alkyl Sulfonate formation. Summary An understanding of the mechanism of formation of Alkyl Sulfonates is critical in order to avoid restricting or over-controlling sulfonic acid salts, which have many technical advantages as pharmaceutical counterions. Recent regulatory acceptance of a human threshold limit dose of 2 mg/kg per day for ethyl methaneSulfonate, indicating that its toxicological risks have previously been considerably overestimated, could signal the beginning of the end over safety concerns on Alkyl Sulfonate residues, thus removing a major constraint from the exploitation of sulfonic acid counterions.
Armen H. Poghosyan - One of the best experts on this subject based on the ideXlab platform.
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Shape of Long Chain Alkyl Sulfonate Micelle upon Salt Addition: a Molecular Dynamics Study
Journal of Surfactants and Detergents, 2015Co-Authors: Armen H. Poghosyan, Levon H. Arsenyan, Aram A. ShahinyanAbstract:Here we report a molecular dynamics simulation on the state of long chain Alkyl Sulfonate micelle which occurs in the presence of salt. We tracked the formation of a large micelle with a dumbbell-like shape, which has hemispherical end caps with a large radius rather than the middle cylindrical body, where the shape bending angle was around 160^o. The data from chain analysis indicate that the micelle hydrocarbon layer is covered with disordered tails. We also report micelle fission controlled by changes in salt concentration. Overall, the parameters obtained are compared with existing experimental findings.
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Long-chain Alkyl Sulfonate micelle fission: a molecular dynamics study
Colloid and Polymer Science, 2014Co-Authors: Armen H. Poghosyan, Levon H. Arsenyan, Aram A. ShahinyanAbstract:In this study, we investigate micelle fission of long-chain Alkyl Sulfonate molecules using atomistic scale simulation. GROMACS software code with the united atom force field was applied. 0.5-μs parallel molecular dynamics simulation study was conducted for a surfactant/water system consisting of 192 sodium pentadecyl Sulfonate and 40,553 water molecules. The large preassembled micelle was ruptured at Krafft above T = 323-K temperature, and we track two ellipsoid-like micelles over the course of the production run. To estimate the micelle shape, we determined the principal moments of inertia and the eccentricity, which proved that the micelles have a pronounced prolate spheroid shape, which agrees well with our previous experimental data. The mechanism of micelle fission was explored in detail. The aggregation number, ionization degree, and other parameters obtained from simulation were consistent with existing experimental finding. The determined parameters in addition to simple visual inspection of trajectories revealed monomer-micelle exchange—with the estimated relaxation time τ _1 = 10^− 9s. We assume that the exchange process is conditioned by the unequal size of micelles leading to adjustment of aggregation number.
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atomic level and coarse grained simulation of long chain Alkyl Sulfonate micelle self assembly
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014Co-Authors: Armen H. Poghosyan, Levon H. Arsenyan, L A Antonyan, Aram A. ShahinyanAbstract:Abstract A series of long runs were performed on pentadecyl Sulfonate/water systems using both atomic level and coarse-grained approaches. Surfactant micelle fusion was observed with coarse-grained approach; however, the atomic scale study did not reach the equilibrium even at long timescales. The shape of micellar aggregate appeared as to be prolate spheroidal rather than spherical. The aggregation number, hydrocarbon tails and water properties were also examined. The comparison data obtained from atomic level and coarse-grained are in agreement with previous reports. In this report self-assembly of micelle formation is discussed. We state that the growth of micelles occurs by gradually coalescence of micellar aggregates. We suggest that with coarse-grained approach equilibrium is achieved at dispersed initial configuration and therefore, the model is ideally suited to describe the dynamical nature of the self-assembly of surfactants.
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molecular dynamics study of intermediate phase of long chain Alkyl Sulfonate water systems
Langmuir, 2013Co-Authors: Armen H. Poghosyan, Levon H. Arsenyan, Aram A. ShahinyanAbstract:Using atomic level simulation we aimed to investigate various intermediate phases of the long chain Alkyl Sulfonate/water system. Overall, about 800 ns parallel molecular dynamics simulation study was conducted for a surfactant/water system consisting of 128 sodium pentadecyl Sulfonate and 2251 water molecules. The GROMACS software code with united atom force field was applied. Despite some differences, the analysis of main structural parameters is in agreement with X-ray experimental findings. The mechanism of self-assembly of SPDS molecules was also examined. At T = 323 K we obtained both tilted fully interdigitated and liquid crystalline-like disordered hydrocarbon chains; hence, the presence of either gel phase that coexists with a lamellar phase or metastable gel phase with fraction of gauche configuration can be assumed. Further increase of temperature revealed that the system underwent a transition to a lamellar phase, which was clearly identified by the presence of fully disordered hydrocarbon cha...
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Molecular dynamics study of intermediate phase of long chain Alkyl Sulfonate/water systems.
Langmuir : the ACS journal of surfaces and colloids, 2012Co-Authors: Armen H. Poghosyan, Levon H. Arsenyan, Aram A. ShahinyanAbstract:Using atomic level simulation we aimed to investigate various intermediate phases of the long chain Alkyl Sulfonate/water system. Overall, about 800 ns parallel molecular dynamics simulation study was conducted for a surfactant/water system consisting of 128 sodium pentadecyl Sulfonate and 2251 water molecules. The GROMACS software code with united atom force field was applied. Despite some differences, the analysis of main structural parameters is in agreement with X-ray experimental findings. The mechanism of self-assembly of SPDS molecules was also examined. At T = 323 K we obtained both tilted fully interdigitated and liquid crystalline-like disordered hydrocarbon chains; hence, the presence of either gel phase that coexists with a lamellar phase or metastable gel phase with fraction of gauche configuration can be assumed. Further increase of temperature revealed that the system underwent a transition to a lamellar phase, which was clearly identified by the presence of fully disordered hydrocarbon cha...
Peng Yan - One of the best experts on this subject based on the ideXlab platform.
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polymer surfactant interaction differences between Alkyl sulfate and Alkyl Sulfonate
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004Co-Authors: Peng Yan, Jin-xin XiaoAbstract:Abstract The interactions between sodium Alkyl sulfates (CnSO4)/sodium Alkyl Sulfonates (CnSO3) and polyethylene oxide (PEO) were studied by surface tension, fluorescence and dynamic light scattering measurements, assisted with quantum-chemical calculations. It was found that, although many properties of CnSO4 and CnSO3 were similar, there were striking differences in their interactions with PEO. Sodium Alkyl Sulfonates were seen to interact more weakly than their sulfate analogs. Such differences were especially distinct when compared C10SO4-PEO with C10SO3-PEO, the former exhibits obvious interactions, but no observable interaction in the latter. With the help of ab initio quantum-chemical calculation, the results were explained.
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Polymer–surfactant interaction: differences between Alkyl sulfate and Alkyl Sulfonate
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004Co-Authors: Peng Yan, Jin-xin XiaoAbstract:Abstract The interactions between sodium Alkyl sulfates (CnSO4)/sodium Alkyl Sulfonates (CnSO3) and polyethylene oxide (PEO) were studied by surface tension, fluorescence and dynamic light scattering measurements, assisted with quantum-chemical calculations. It was found that, although many properties of CnSO4 and CnSO3 were similar, there were striking differences in their interactions with PEO. Sodium Alkyl Sulfonates were seen to interact more weakly than their sulfate analogs. Such differences were especially distinct when compared C10SO4-PEO with C10SO3-PEO, the former exhibits obvious interactions, but no observable interaction in the latter. With the help of ab initio quantum-chemical calculation, the results were explained.
