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Yuriy F. Zuev - One of the best experts on this subject based on the ideXlab platform.
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Brownian dynamics simulation of substrate motion near active site of enzyme entrapped inside Reverse Micelle.
European Biophysics Journal, 2010Co-Authors: Elena A Ermakova, Natalia L Zakhartchenko, Yuriy F. ZuevAbstract:Brownian dynamics simulation has been applied to analyze the influence of the electrostatic field of a Reverse Micelle on the enzyme-substrate complex formation inside a Micelle. The probability that the enzyme-substrate complex will form from serine protease (trypsin) and the specific hydrophilic cationic substrate Nα-benzoyl-l-arginine ethyl ester has been studied within the framework of the encounter complex formation theory. It has been shown that surfactant charge, dipole moments created by charged surfactant molecules and counterions, and permittivity of the inner core of Reverse Micelles can all be used as regulatory parameters to alter the substrate orientation near the active site of the enzyme and to change the probability that the enzyme-substrate complex will form.
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effect of surface potential of Reverse Micelle on enzyme substrate complex formation
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2008Co-Authors: Elena A Ermakova, Natalia L Zakhartchenko, Yuriy F. ZuevAbstract:Abstract The influence of the electrostatic potential of Reverse Micelle on the enzyme–substrate complex formation have been studied within the framework of the encounter complex (EC) formation theory. Reverse Micelles have a multiple-factor effect on encapsulated substances and on mechanisms of their interaction. The action of individual constituents on the overall micellar effect was analyzed by means of Brownian dynamics simulation. The effects of surface potential in charged and neutral Reverse Micelles, of the size and of the ionic strength of micellar core on the probability to form the reaction complex between serine protease (trypsin) and specific substrate Nα-benzoyl- l -arginine ethyl ester was examined. It was shown that negative potential of Micelle increases the probability of EC formation and the positive potential decreases it. Orientation of substrate in electrostatic field of Micelle depends on the value and the sign of surface potential.
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Effect of surface potential of Reverse Micelle on enzyme–substrate complex formation
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2008Co-Authors: Elena A Ermakova, Natalia L Zakhartchenko, Yuriy F. ZuevAbstract:Abstract The influence of the electrostatic potential of Reverse Micelle on the enzyme–substrate complex formation have been studied within the framework of the encounter complex (EC) formation theory. Reverse Micelles have a multiple-factor effect on encapsulated substances and on mechanisms of their interaction. The action of individual constituents on the overall micellar effect was analyzed by means of Brownian dynamics simulation. The effects of surface potential in charged and neutral Reverse Micelles, of the size and of the ionic strength of micellar core on the probability to form the reaction complex between serine protease (trypsin) and specific substrate Nα-benzoyl- l -arginine ethyl ester was examined. It was shown that negative potential of Micelle increases the probability of EC formation and the positive potential decreases it. Orientation of substrate in electrostatic field of Micelle depends on the value and the sign of surface potential.
Olivia A Graeve - One of the best experts on this subject based on the ideXlab platform.
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Reverse Micelle synthesis of oxide nanopowders mechanisms of precipitate formation and agglomeration effects
Journal of Colloid and Interface Science, 2013Co-Authors: Olivia A Graeve, Hoorshad Fathi, James P Kelly, Michael S Saterlie, Kaustav Sinha, G Rojasgeorge, Raghunath Kanakala, David R Brown, Enrique A LopezAbstract:Abstract We present an analysis of Reverse Micelle stability in four model systems. The first two systems, composed of unstable microemulsions of isooctane, water, and Na-AOT with additions of either iron sulfate or yttrium nitrate, were used for the synthesis of iron oxide or yttrium oxide powders. These oxide powders were of nanocrystalline character, but with some level of agglomeration that was dependent on calcination temperature and cleaning procedures. Results show that even though the Reverse micellar solutions were unstable, nanocrystalline powders with very low levels of agglomeration could be obtained. This effect can be attributed to the protective action of the surfactant on the surfaces of the powders that prevents neck formation until after all the surfactant has volatilized. A striking feature of the IR spectra collected on the iron oxide powders is the absence of peaks in the ∼1715 cm −1 to 1750 cm −1 region, where absorption due to the symmetric C O (carbonyl) stretching occurs. The lack of such peaks strongly suggests the carbonyl group is no longer free, but is actively participating in the surfactant-precipitate interaction. The final two microemulsion systems, containing CTAB as the surfactant, showed that loss of control of the Reverse Micelle synthesis process can easily occur when the amount of salt in the water domains exceeds a critical concentration. Both model systems eventually resulted in agglomerated powders of broad size distributions or particles that were large compared to the sizes of the Reverse Micelles, consistent with the notion that the microemulsions were not stable and the powders were precipitated in an uncontrolled fashion. This has implications for the synthesis of nanopowders by Reverse Micelle synthesis and provides a benchmark for process control if powders of the highest quality are desired.
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ionic concentration effects on Reverse Micelle size and stability implications for the synthesis of nanoparticles
Langmuir, 2012Co-Authors: Hoorshad Fathi, James P Kelly, Victor R Vasquez, Olivia A GraeveAbstract:We present a systematic investigation and analysis of the structure and stability of Reverse Micelle systems with the addition of NH4OH, ZrOCl2, and Al(NO3)3 salts. We demonstrate that the Reverse Micelle size decreases with increasing salt additions until one reaches a critical concentration, which characterizes the onset of system destabilization. The concept of an electrical double layer, as it applies to Reverse Micelles, is considered for explaining features of destabilization, including the initial decrease in Reverse Micelle size, the destabilization concentration, and the effect of cation valence. We propose that the reduction in size prior to instability is caused by compression of the Reverse Micelle electrical double layers, as higher concentrations of salts are present. The reduced thickness of the electrical double layers allows the decaying potentials to move into closer proximity to each other before generating enough repulsion to balance the forces for Reverse Micelle formation and form a ...
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stability and comparative analysis of aot water isooctane Reverse Micelle system using dynamic light scattering and molecular dynamics
Journal of Physical Chemistry B, 2011Co-Authors: Victor R Vasquez, B C Williams, Olivia A GraeveAbstract:We use molecular dynamics (MD) and dynamic light scattering (DLS) measurements to analyze the size of Reverse micellar structures in the AOT−water−isooctane system at different water-to-surfactant ratios at ambient temperature and pressure. We find good qualitative agreement for the size and morphology behavior of the Reverse Micelle structures between molecular dynamics calculations and DLS measurements; however, the average values for the Reverse Micelle size distributions are systematically larger for the DLS measurements. The latter tends to capture the average hydrodynamic size of the structures based on self-diffusion rather than the average physical size as measured in MD simulations, explaining the systematic deviations observed. The combination of MD with DLS allows a better interpretation of the experimental results, in particular for conditions where the structures are nonspherical, commonly observed at lower water-to-surfactant ratios. We also present and analyze the effect of zirconyl chlorid...
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stability and comparative analysis of aot water isooctane Reverse Micelle system using dynamic light scattering and molecular dynamics
Journal of Physical Chemistry B, 2011Co-Authors: Victor R Vasquez, B C Williams, Olivia A GraeveAbstract:We use molecular dynamics (MD) and dynamic light scattering (DLS) measurements to analyze the size of Reverse micellar structures in the AOT-water-isooctane system at different water-to-surfactant ratios at ambient temperature and pressure. We find good qualitative agreement for the size and morphology behavior of the Reverse Micelle structures between molecular dynamics calculations and DLS measurements; however, the average values for the Reverse Micelle size distributions are systematically larger for the DLS measurements. The latter tends to capture the average hydrodynamic size of the structures based on self-diffusion rather than the average physical size as measured in MD simulations, explaining the systematic deviations observed. The combination of MD with DLS allows a better interpretation of the experimental results, in particular for conditions where the structures are nonspherical, commonly observed at lower water-to-surfactant ratios. We also present and analyze the effect of zirconyl chloride on the micellar size distributions in this system. These type of salts are common for Reverse micellar synthesis processes. We find that zirconyl chloride affects significantly the size distributions.
Elena A Ermakova - One of the best experts on this subject based on the ideXlab platform.
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Brownian dynamics simulation of substrate motion near active site of enzyme entrapped inside Reverse Micelle.
European Biophysics Journal, 2010Co-Authors: Elena A Ermakova, Natalia L Zakhartchenko, Yuriy F. ZuevAbstract:Brownian dynamics simulation has been applied to analyze the influence of the electrostatic field of a Reverse Micelle on the enzyme-substrate complex formation inside a Micelle. The probability that the enzyme-substrate complex will form from serine protease (trypsin) and the specific hydrophilic cationic substrate Nα-benzoyl-l-arginine ethyl ester has been studied within the framework of the encounter complex formation theory. It has been shown that surfactant charge, dipole moments created by charged surfactant molecules and counterions, and permittivity of the inner core of Reverse Micelles can all be used as regulatory parameters to alter the substrate orientation near the active site of the enzyme and to change the probability that the enzyme-substrate complex will form.
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effect of surface potential of Reverse Micelle on enzyme substrate complex formation
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2008Co-Authors: Elena A Ermakova, Natalia L Zakhartchenko, Yuriy F. ZuevAbstract:Abstract The influence of the electrostatic potential of Reverse Micelle on the enzyme–substrate complex formation have been studied within the framework of the encounter complex (EC) formation theory. Reverse Micelles have a multiple-factor effect on encapsulated substances and on mechanisms of their interaction. The action of individual constituents on the overall micellar effect was analyzed by means of Brownian dynamics simulation. The effects of surface potential in charged and neutral Reverse Micelles, of the size and of the ionic strength of micellar core on the probability to form the reaction complex between serine protease (trypsin) and specific substrate Nα-benzoyl- l -arginine ethyl ester was examined. It was shown that negative potential of Micelle increases the probability of EC formation and the positive potential decreases it. Orientation of substrate in electrostatic field of Micelle depends on the value and the sign of surface potential.
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Effect of surface potential of Reverse Micelle on enzyme–substrate complex formation
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2008Co-Authors: Elena A Ermakova, Natalia L Zakhartchenko, Yuriy F. ZuevAbstract:Abstract The influence of the electrostatic potential of Reverse Micelle on the enzyme–substrate complex formation have been studied within the framework of the encounter complex (EC) formation theory. Reverse Micelles have a multiple-factor effect on encapsulated substances and on mechanisms of their interaction. The action of individual constituents on the overall micellar effect was analyzed by means of Brownian dynamics simulation. The effects of surface potential in charged and neutral Reverse Micelles, of the size and of the ionic strength of micellar core on the probability to form the reaction complex between serine protease (trypsin) and specific substrate Nα-benzoyl- l -arginine ethyl ester was examined. It was shown that negative potential of Micelle increases the probability of EC formation and the positive potential decreases it. Orientation of substrate in electrostatic field of Micelle depends on the value and the sign of surface potential.
Natalia L Zakhartchenko - One of the best experts on this subject based on the ideXlab platform.
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Brownian dynamics simulation of substrate motion near active site of enzyme entrapped inside Reverse Micelle.
European Biophysics Journal, 2010Co-Authors: Elena A Ermakova, Natalia L Zakhartchenko, Yuriy F. ZuevAbstract:Brownian dynamics simulation has been applied to analyze the influence of the electrostatic field of a Reverse Micelle on the enzyme-substrate complex formation inside a Micelle. The probability that the enzyme-substrate complex will form from serine protease (trypsin) and the specific hydrophilic cationic substrate Nα-benzoyl-l-arginine ethyl ester has been studied within the framework of the encounter complex formation theory. It has been shown that surfactant charge, dipole moments created by charged surfactant molecules and counterions, and permittivity of the inner core of Reverse Micelles can all be used as regulatory parameters to alter the substrate orientation near the active site of the enzyme and to change the probability that the enzyme-substrate complex will form.
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effect of surface potential of Reverse Micelle on enzyme substrate complex formation
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2008Co-Authors: Elena A Ermakova, Natalia L Zakhartchenko, Yuriy F. ZuevAbstract:Abstract The influence of the electrostatic potential of Reverse Micelle on the enzyme–substrate complex formation have been studied within the framework of the encounter complex (EC) formation theory. Reverse Micelles have a multiple-factor effect on encapsulated substances and on mechanisms of their interaction. The action of individual constituents on the overall micellar effect was analyzed by means of Brownian dynamics simulation. The effects of surface potential in charged and neutral Reverse Micelles, of the size and of the ionic strength of micellar core on the probability to form the reaction complex between serine protease (trypsin) and specific substrate Nα-benzoyl- l -arginine ethyl ester was examined. It was shown that negative potential of Micelle increases the probability of EC formation and the positive potential decreases it. Orientation of substrate in electrostatic field of Micelle depends on the value and the sign of surface potential.
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Effect of surface potential of Reverse Micelle on enzyme–substrate complex formation
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2008Co-Authors: Elena A Ermakova, Natalia L Zakhartchenko, Yuriy F. ZuevAbstract:Abstract The influence of the electrostatic potential of Reverse Micelle on the enzyme–substrate complex formation have been studied within the framework of the encounter complex (EC) formation theory. Reverse Micelles have a multiple-factor effect on encapsulated substances and on mechanisms of their interaction. The action of individual constituents on the overall micellar effect was analyzed by means of Brownian dynamics simulation. The effects of surface potential in charged and neutral Reverse Micelles, of the size and of the ionic strength of micellar core on the probability to form the reaction complex between serine protease (trypsin) and specific substrate Nα-benzoyl- l -arginine ethyl ester was examined. It was shown that negative potential of Micelle increases the probability of EC formation and the positive potential decreases it. Orientation of substrate in electrostatic field of Micelle depends on the value and the sign of surface potential.
Mahavir Singh - One of the best experts on this subject based on the ideXlab platform.
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Influence of Ni doping on physical properties of La_0.7Sr_0.3FeO_3 synthesized by Reverse Micelle technique
Journal of Materials Science: Materials in Electronics, 2021Co-Authors: Abdullah Ameen Saad Hassan, Mahavir Singh, Wasi Khan, Shahid Husain, Pooja Dhiman, Meznah M. AlanaziAbstract:In the present work, a series of Ni-doped La_0.7Sr_0.3FeO_3 perovskite nanostructures with chemical composition La_0.7Sr_0.3Fe_1− x Ni_ x O_3 ( x = 0.0, 0.01 and 0.04) were synthesized by the Reverse Micelle (RM) technique. The X-ray diffraction (XRD) analysis verifies good crystallinity and an orthorhombic crystal structure of the samples. The remarkable growth of the crystallites was observed in increasing the amount of Ni doping. The morphology, topography, and chemical composition were investigated through field emission scanning electron microscope (FESEM) equipped with an energy dispersive X-ray spectrometer (EDS). The FESEM/EDS measurements confirm uniform morphology and interconnected nature of the particles with relevant elements. The Fourier transform infrared (FTIR) spectra further demonstrate the perovskite structure through Fe/Ni–O asymmetric stretching and deformation of Fe/Ni–O–Fe/Ni bending vibrations in the lattice. A systematic reduction in the bandgap ( E _ g ) is noticed upon the Ni doping in La_0.7Sr_0.3FeO_3, as estimated from the UV/visible spectra by employing the Tauc's relation. A distinct behaviour of dielectric properties was revealed as a function of frequency and temperature for all the samples. The dielectric constant ( ε ′), dielectric loss (tan δ ), and ac conductivity ( σ _ ac ) were measured at selected frequencies and temperatures. The results signify that the dielectric nature was frequency-dependent and thermally stimulated. The magnetic properties at room temperature indicate weak ferromagnetism with gradual increase in the maximum magnetization and coercivity with the increase in Ni concentration.
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nickel zinc ferrite from Reverse Micelle process structural and magnetic properties mossbauer spectroscopy characterization
Journal of Physical Chemistry C, 2009Co-Authors: Sangeeta Thakur, S C Katyal, Ajay Gupta, V R Reddy, S K Sharma, M Knobel, Mahavir SinghAbstract:Nickel−zinc ferrite (Ni0.58Zn0.42Fe2O4) nanoparticles with an average crystallite size of about 8.4 nm were synthesized by Reverse Micelle technique. Bulk sample was prepared by annealing nickel−zinc ferrite (NZFO) nanoparticles at 1473 K. Room temperature Mossbauer spectra of NZFO nanoparticles exhibit collective magnetic excitations, while annealed (bulk) NZFO particles have the ferrimagnetic phase. At 5 K, the broad shape of Mossbauer spectral lines for nanoparticles in comparison to bulk particles provide clear evidence of a wide distribution of magnetic fields acting at the Fe3+ nuclei in the nanoparticles. Bulk NZFO particles and inner core of nanoparticles exhibit a fully inverse spinel structure with a Neel type collinear spin arrangement, whereas the major feature of the ionic and spin configuration in the grain boundary (surface) region are a nonequilibrium cation distribution and a canted spin arrangement. The cation distribution of nano and bulk particles has been studied by using in-field Mos...
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structural and magnetic properties of nano nickel zinc ferrite synthesized by Reverse Micelle technique
Journal of Magnetism and Magnetic Materials, 2009Co-Authors: Sangeeta Thakur, S C Katyal, Mahavir SinghAbstract:Abstract Nanocrystalline nickel–zinc ferrites (Ni0.58Zn0.42Fe2O4) at different pH values (less than 9.6, 9.6, 10.96, and 11.40) for the alkali-precipitating reaction were synthesized by Reverse Micelle technique. X-ray diffraction reveals a well-defined nickel–zinc ferrite crystal phase at pH=9.6. Increase in pH value obstructs pure-phase formation and results in partial formation of α-Fe2O3. The magnetic behaviour of the samples was studied by superconducting quantum interference device. All the samples show superparamagnetic behaviour at room temperature (300 K) and negligible hysteresis at low temperature (5 K). The low value of saturation magnetization is explained on the basis of spin canting. The high-field irreversibility and shifting of the hysteresis loop detected in single-phase sample has been assigned to a spin-disordered phase, which has a spin-freezing temperature of approximately 42 K and other two samples have an antiferromagnetic phase (α-Fe2O3) coupled to the ferromagnetic phase.
