scholarly journals A theoretical study on the expression of enzymic activity in reverse micelles

1989 ◽  
Vol 259 (2) ◽  
pp. 355-361 ◽  
Author(s):  
R Bru ◽  
A Sánchez-Ferrer ◽  
F Garcia-Carmona
Keyword(s):  
Reverse Micelle ◽  
Reverse Micelles ◽  
Structural Model ◽  
Dynamic Equilibrium ◽  
Free Water ◽  
Continuous Phase ◽  
Enzymic Activity ◽  
Water Dynamics ◽  
Polar Phase ◽  
Catalytic Constant

The present work deals with a theoretical model of catalysis by enzymes entrapped in reverse micelles. Three aspects of the enzyme-reverse-micelle system have been considered: structure, dynamics and enzyme distribution and catalysis in reverse micelles. A proposed structural model of reverse micelles [El Seoud (1984) in Reverse Micelles (Luisi, P. L. & Straub, B. E., eds.), p. 81, Plenum Press, New York] consists of three domains: surfactant apolar tails, bound water and free water. Dynamics are based on a dynamic equilibrium of association-dissociation that lead one to consider the dispersed polar phase as a pseudo-continuous phase [Luisi, Giomini, Pileni & Robinson (1988) Biochim. Biophys. Acta 947, 207-246]. Enzyme is distributed among the reverse-micelle domains and it expresses a catalytic constant for each one of them. The overall activity is calculated taking into account the volume in which enzyme is solubilized, and expressed as a function of the whole volume (V). The characteristic parameters of reverse micelles, omega 0 (= [H2O]/[surfactant]) and theta (= % water, v/v), were investigated as modulators of enzymic activity. Three basic patterns of modulation by omega 0 were found depending on which domain the enzyme expressed the highest catalytic constant. Combinations of those basic patterns lead to other modulation types that can be found experimentally, such as superactivation. Other combinations predict behaviour patterns not described to date, such as superinhibition. Dependence of catalytic activity on theta was only stated at omega 0 values around a critical value, which coincides with the appearance of free water.

scholarly journals The effect of substrate partitioning on the kinetics of enzymes acting in reverse micelles

1990 ◽  
Vol 268 (3) ◽  
pp. 679-684 ◽  
Author(s):  
R Bru ◽  
A Sánchez-Ferrer ◽  
F García-Carmona
Keyword(s):  
Reverse Micelle ◽  
Substrate Concentration ◽  
Reverse Micelles ◽  
Bound Water ◽  
Free Water ◽  
Enzymic Activity ◽  
Molar Ratio ◽  
Biphasic Model ◽  
Catalytic Constant ◽  
Kinetics Of

A theoretical model for the expression of enzymic activity in reverse micelles previously developed [Bru. Sánchez-Ferrer & García-Carmona (1989) Biochem. J. 259, 355-361] was extended in the present work. The substrate concentration in each reverse-micelle phase (free water, bound water and surfactant apolar tails) and the organic solvent was expressed as a function of the total substrate concentration, taking into account its partition coefficients, that is, partitioning of the substrate in a multiphasic system. In each phase the enzyme expresses a catalytic constant and a Km. Thus the whole reaction rate is the addition of the particular rates expressed in each domain. This model was compared with that developed for a biphasic system [Levashov, Klyachko, Pantin, Khmelnitski & Martinek (1980) Bioorg. Khim. 6, 929-943] by fitting the experimental results obtained with mushroom tyrosinase (working on both 4-t-butylcatechol and 4-methylcatechol) to the two models. The parameters which characterize reverse micelles, omega 0 (water/surfactant molar ratio) and theta (fraction of water) were investigated. The omega 0 profile was shown to be hyperbolic for both substrates. Activity towards 4-t-butylcatechol decreases as theta increases, this observation being attributable to a dilution of the substrate. A Km of 7.8 M for 4-t-butylcatechol could be calculated on the basis of the biphasic model, whereas it was 13.5 mM when calculating on the basis of our model. A new parameter, rho (= [substrate]/theta), was defined to characterize those substrates that mainly solubilize in the reverse micelle (‘micellar substrates’).

Rotational Reorientation Dynamics of Aerosol-OT Reverse Micelles Formed in Nearcritical Propane

1996 ◽  
Vol 50 (6) ◽  
pp. 732-739 ◽  
Author(s):  
Mark P. Heitz ◽  
Frank V. Bright
Keyword(s):  
Reverse Micelle ◽  
Reverse Micelles ◽  
Lateral Diffusion ◽  
Continuous Phase ◽  
Interfacial Region ◽  
Experimental Conditions ◽  
Correlation Times ◽  
Aerosol Ot ◽  
Rotational Correlation Times ◽  
Rotational Correlation

The rotational reorientation kinetics of two fluorescent solutes (rhodamine 6G, R6G, and rhodamine 101, R101) have been determined in sodium bis(2-ethylhexyl) sulfosuccinate (Aerosol-OT, AOT) reverse micelles formed in liquid and nearcritical propane. We show that the amount of water loading ([water]/[AOT], R), continuous phase density, and temperature all influence the solute rotational dynamics. In all cases, the decay of anisotropy data (i.e., frequency-dependent differential polarized phase angle and polarized modulation ratio) are well-described by a bi-exponential decay law. We find that the faster rotational correlation times are similar to but slightly less than the values predicted for an individual AOT reverse micelle rotating in propane. The recovered rotational correlation times range from 200 to 500 ps depending on experimental conditions. This faster rotational process is explained in terms of lateral diffusion of the fluorophore along the water/headgroup interfacial region within the reverse micelle. The recovered values for the slower rotational correlation times range from 7 to 18 ns. These larger rotational reorientation times are assigned to varying micelle-micelle (i.e., tail-tail) interactions in the low-density, highly compressible fluid region. We also quantify the contribution of the reverse micellar “aggregate” to the total decay of anisotropy.

Improvement of monodispersity and shape symmetry of silica shell for PbS quantum dots by introducing surface silanization and adjusting reverse micelle size

2021 ◽  
Author(s):  
Kohki MUKAI ◽  
Kosuke Ikeda ◽  
Reo Hatta
Keyword(s):  
Reverse Micelle ◽  
Reverse Micelles ◽  
Silica Coating ◽  
Silica Shell ◽  
Raw Material ◽  
Shell Formation ◽  
Shell Size ◽  
Surface Control ◽  
Micelle Size ◽  
Pbs Quantum Dots

Abstract Increasing the thickness of the quantum dot silica coating layer reduces monodispersity and shape symmetry. This paper reports three effective ways to solve this problem and achieve a large silica-coated QDs, i.e., proper silanization on the QD surface, control of reverse micelle size by adjusting the amount of QD solvent, and two-step formation of silica shell. Proper substitution of ligands on the QD surface in the early stages of silica shell formation was important for uniform coating reaction. An amount of toluene as QD solvent determined the size of reverse micelles during the silica shell formation. There was an optimum combination of inverse micelle size and silica shell size to obtain silica-coated QDs with good monodispersity and high shape symmetry. We succeeded in growing the thick silica shell with expanding reverse micelle size by additionally supplying toluene with the raw material using the optimum silica-coated QDs as growth nucleus

Geometry and Nanolength Scales versus Interface Interactions: Water Dynamics in AOT Lamellar Structures and Reverse Micelles

2009 ◽  
Vol 131 (23) ◽  
pp. 8318-8328 ◽  
Author(s):  
David E. Moilanen ◽  
Emily E. Fenn ◽  
Daryl Wong ◽  
M. D. Fayer
Keyword(s):  
Reverse Micelles ◽  
Water Dynamics ◽  
Lamellar Structures

Supramolecular solvent-based microextraction of copper and lead in water samples prior to reacting with synthesized Schiff base by flame atomic absorption spectrometry determination

2014 ◽  
Vol 6 (7) ◽  
pp. 2294-2298 ◽  
Author(s):  
Zonghao Li ◽  
Jiaxi Chen ◽  
Mousheng Liu ◽  
Yaling Yang
Keyword(s):  
Atomic Absorption Spectrometry ◽  
Atomic Absorption ◽  
Flame Atomic Absorption Spectrometry ◽  
Water Samples ◽  
Reverse Micelles ◽  
Absorption Spectrometry ◽  
Continuous Phase ◽  
Nonanoic Acid ◽  
Flame Atomic Absorption ◽  
Supramolecular Solvent

A supramolecular solvent made up of reverse micelles of nonanoic acid, dispersed in a continuous phase of tetrahydrofuran and water allows simple, rapid and efficient microextraction of copper and lead in water samples prior to flame atomic absorption spectrometry determination.

How Does the Urea Dynamics Differ from Water Dynamics inside the Reverse Micelle?

2011 ◽  
Vol 115 (38) ◽  
pp. 10398-10407 ◽  
Author(s):  
Abhigyan Sengupta ◽  
Rahul V. Khade ◽  
Partha Hazra
Keyword(s):  
Reverse Micelle ◽  
Water Dynamics

scholarly journals Shrinking, Growing, and Bursting: Microfluidic Equilibrium Control of Water-in-Water Droplets

2021 ◽  
Author(s):  
Byeong-Ui Moon ◽  
Dae Kun Hwang ◽  
Scott S. H. Tsai
Keyword(s):  
Dynamic Equilibrium ◽  
Polymer Concentration ◽  
Dynamic Control ◽  
Microfluidic Channel ◽  
Continuous Phase ◽  
Phase System ◽  
Two Phase ◽  
Equilibrium Control ◽  
Tie Lines

We demonstrate the dynamic control of aqueous two phase system (ATPS) droplets in shrinking, growing, and dissolving conditions. The ATPS droplets are formed passively in a flow focusing microfluidic channel, where the dextran-rich (DEX) and polyethylene glycol-rich (PEG) solutions are introduced as disperse and continuous phases, respectively. To vary the ATPS equilibrium condition, we infuse into a secondary inlet the PEG phase from a different polymer concentration ATPS. We find that the resulting alteration of the continuous PEG phase can cause droplets to shrink or grow by approximately 45 and 30 %, respectively. This volume change is due to water exchange between the disperse DEX and continuous PEG phases, as the system tends towards new equilibria. We also develop a simple model, based on the ATPS binodal curve and tie lines, that predicts the amount of droplet shrinkage or growth, based on the change in the continuous phase PEG concentration. We observe a good agreement between our experimental results and the model. Additionally, we find that, when the continuous phase PEG concentration is reduced such that PEG and DEX phases no longer phase separate, the ATPS droplets are dissolved into the continuous phase. We apply this method to controllably release encapsulated microparticles and cells, and we find that their release occurs within 10 seconds. Our approach uses the dynamic equilibrium of ATPS to control droplet size along the microfluidic channel. By modulating the ATPS equilibrium, we are able to shrink, grow, and dissolve ATPS droplets in situ. We anticipate that this approach may find utility in many biomedical settings, for example, in drug and cell delivery and release applications.

scholarly journals On the characterization of NaDEHP/n-heptane nonaqueous reverse micelles: the effect of the polar solvent

2015 ◽  
Vol 17 (10) ◽  
pp. 7002-7011 ◽  
Author(s):  
Silvina S. Quintana ◽  
R. Dario Falcone ◽  
Juana J. Silber ◽  
Fernando Moyano ◽  
N. Mariano Correa
Keyword(s):  
Reverse Micelle ◽  
Reverse Micelles ◽  
Polar Solvent ◽  
The Novel ◽  
Schematic Representation

Schematic representation of different interfaces in the novel nonaqueous NaDEHP/n-heptane reverse micelle.

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