Water In Reverse Micelles Research Articles

The self-assembly of water reverse micelles with imidazolium ionic liquids in supercritical carbon dioxide: A molecular dynamics simulation study

Molecular dynamics (MD) simulations were employed to investigate the self-assembly of water reverse micelles (RMs) with imidazolium ionic liquids (ILs) stabilized by dodecyl polyoxyethylene (3) polyoxypropylene (6) ether (LS-36) in supercritical carbon dioxide (scCO2) at 308 K and 20 MPa. The study explored the impact of various factors, including the IL concentration, the alkyl chain length of the imidazolium cations (1-ethyl-3-methylimidazolium [EMIM]+, 1-octyl-3-methylimidazolium [OMIM]+), and the anion type (bis(trifluoromethylsulfonyl)imide [NTf2]-, tetrafluoroborate [BF4]-, acetate [ACE]-) on the solubilization of ILs by water reverse micelles. The findings revealed that water, ILs, and the surfactant formed spherical RMs in the fluid phase, with varying structures depending on the hydrophobicity of the IL. The presence of ILs was found to expedite the self-assembly process and increase the number of assembled surfactants. Higher IL concentrations resulted in greater water content in the polar core of the RMs and reduced water solubility in scCO2. The intermolecular interactions occurring between components of the systems as well as dynamical properties are discussed in terms of radial distribution functions, density distribution, hydrogen bond number and lifetime, number of contacts, and self-diffusion coefficients.

Anomalously Large Heat Generation of Hydration Water under Microwave Irradiation.

Much attention has been paid to the biological effects of microwave irradiation. The hydration water surrounding a biomolecule is crucial in its biological reactions and functions. Therefore, it is important to know the response of hydration water to microwaves to understand their biological effects; however, the scarcity of studies about it often leads to speculations and debates about that effect. In this study, we have made real-time temperature measurements of reverse micellar solutions with their water droplet size from ∼2.3 to ∼9.5 nm using a waveguide system combined with a microwave generator at 2.45 GHz. The heat generated by water in reverse micelles has been observed to depend on their size. It is about 10 times larger than that of liquid water at their small sizes (<∼3.5 nm) and diminishes with further enlarging the size, approaching the water's value at their large sizes (∼10 nm). These results indicate that the heat generation behavior has an interfacial effect; specifically, the hydration water on the surfactant layer produces heat 10 times larger than bulk water. Moreover, the hydration number per surfactant molecule decreases in a core-shell model with increasing the reverse micelle size. These features are also reflected in the heat generation rate. Our findings may offer a new and fundamental perspective for studies on the biological effects of microwave irradiation.

Molecular-Level investigation of AOT reverse micelle water content for preserving chymotrypsin's native structure using MD simulation

The molecular dynamics simulation approach has been effectively employed to determine suitable activity conditions of chymotrypsin (α-CT) within a range of nano-pools. Results from eleven molecular dynamics simulations were presented, which were performed in ten water-AOT-isooctane reverse micelles and a bulk aqueous solution. Half of the RMs are empty, and the other half are loaded with α-CT in their water pools. Each batch of five RMs is studied in five different compositions of 3, 5, 10, 15 and 20 water-to-surfactant concentration ratios (W0) at ambient temperature and pressure. The simulation is not started from generally predefined geometric structures. Our simulations all started from random molecular configurations and then allowed sufficient simulation time for the system to reach equilibrium. The general shapes of RMs without protein cores are elongated ellipsoids at low W0 values and quasi-spherical at higher W0 values, while the overall shapes of RMs with protein cores are quasi-spherical and almost independent of W0 values. Previously published experimental data strongly support the results of our predicted simulated structures and analyzed dynamics. In both the simulated RM and the experimentally well-studied α-CT protein within RM at W0 15, the dynamics and structure closely mirror those of the actual bulk water environment. The shift in behavior was identified that led to the alteration of the protein structure's activity during the increase in water content of reverse micelles between W0 15 and 20. Overall, the rise in surface area interaction between the protein and nonpolar iso-Octane can be attributed to the reduction in surfactant coverage, causing the transition from W0 15 to 20.

Insights into the self-assembly of water reverse micelles and solubilization process in liquid and supercritical solvents: A molecular dynamics study

This article reports on a full-atomic classical molecular dynamics simulation investigating the self-assembly process of reverse micelles in carbon tetrachloride and supercritical carbon dioxide (scCO2). The study explores the impact of solvent type, surfactant structure (sodium dodecyl sulfate and sodium bis(3,5,5-trimethyl-1-hexyl) sulfosuccinate), water/surfactant ratio, and surfactant concentration on the self-assembly, size, and shape of reverse micelles. The results indicate that at low water/surfactant ratios in scCO2, irregularly shaped reverse micelles are formed, whereas spherical micelles form as the water/surfactant ratio increases. In scCO2, there is always a small fraction of free water molecules present, whereas in CCl4, all water molecules are surrounded by surfactants. The distribution of head groups of di-chain surfactants over the surface of micelles is observed to occur in groups of several surfactants, forming salt bridges through sodium cations. The solubilization of methyl orange by reverse micelles in pure scCO2 and scCO2 modified with ethanol has also been investigated. The study reveals that the hydrophilic part of the solute is located in the water core of the micelle, while the tail is positioned in the hydrophobic crown. Moreover, the presence of ethanol increases the number of reverse micelles compared to the system without ethanol. Ethanol molecules primarily reside on the surface of the water core, forming stable hydrogen bonds with surfactants, as well as shorter-lived hydrogen bonds with water molecules.

Extended molar absorption analysis of confined states of water in reverse micelles using near-infrared spectroscopy

The properties of nanoscale water pools in reverse micelles (RMs) are significantly different from those of bulk water because of the influence of polar groups and spatial confinement. It was commonly accepted that water in RMs exists in two forms: interfacial water near the surfactant polar groups and core water in the central region away from the polar groups, however, it is difficult to detect two distinct forms. The near-infrared spectra of water inside the RMs formed by four surfactants were measured, and the spectra of bulk water-like core water were detected by an extended molar absorption analysis.

Properties of Water in Reverse Micelles

The key role of self-organization processes in the formation of stable nanoparticles of various metals (Fe, Au, Rh, Re, Pd) in reverse micelles (acting as microreactors) is experimentally confirmed. An important property of the water pools of reverse micelles is also confirmed: the water in these pools is in the polarized state and can reduce metal ions.

Role of Different States of Solubilized Water on Solvation Dynamics and Rotational Relaxation of Coumarin 490 in Reverse Micelles of Gemini Surfactants, Water/12-s-12.2Br- (s = 5, 6, 8)/n-Propanol/Cyclohexane.

The present study demonstrates how the different states of solubilized water viz. quaternary ammonium headgroup-bound, bulklike, counterion-bound, and free water in reverse micelles of a series of cationic gemini surfactants, water/12-s-12 (s = 5, 6, 8).2Br–/n-propanol/cyclohexane, control the solvation dynamics and rotational relaxation of Coumarin 490 (C-490) and microenvironment of the reverse micelles. The relative number of solubilized water molecules of a given state per surfactant molecule decides major and minor components. A rapid increase in the number of bulklike water molecules per surfactant molecule as compared to the slow increase in the number of each of headgroup- and counterion-bound water molecules per surfactant molecule with increasing water content (Wo) in a given reverse micellar system is responsible for the increase in the rate of solvation and rotational relaxation of C-490. The increase in the number of counterion-bound water molecules per surfactant molecule and the concomitant decrease in the number of bulklike water molecules per surfactant molecule with increasing spacer chain length of gemini surfactants at a given Wo are ascribed to the slower rates of both solvation and rotational relaxation. Relative abundances of different states of water have a role on the microenvironment of the reverse micelles as well. Thus, a comprehensive effect of different states of water on dynamics in complex biomimicking systems has been presented here.

Water Structure and Dynamics in the Stern Layer of Micelles: Femtosecond Mid-Infrared Pump-Probe Spectroscopy Study.

Molecular-level understanding of the water structure and dynamics in the Stern layer of micelles is important to elucidate the active role of water in biological processes on membrane surfaces. Micelles and reverse micelles are considered to be excellent membrane model systems. Here, to address the question of whether or not the spatial confinement effect on water in reverse micelles and nanometric water pool systems plays a role in modulating water dynamics, we consider four different aqueous micelle solutions and study the water dynamics in the Stern layer of micelles using a femtosecond mid-infrared pump-probe spectroscopy technique. Vibrational energy relaxation and rotational dynamics of the O?D stretch mode of HDO and the azido stretch mode of hydrazoic acid are critically dependent on the charge, polarity, and chemical structure of the surfactant head group. In particular, water molecules in the Stern layer of micelles, which are not in spatially confined environments, are notably different from those in bulk water. This finding clearly indicates that changes in the vibrational and rotational dynamics of water molecules, even in spatially confined systems, are mainly induced by surface effects instead of spatial confinement effects. We believe that the present experimental results are of importance for understanding water-involved biochemical processes on biological membranes.

The Effect of Hydroxyl Groups on Solubilization of Pyridine Derivatives in Span 80–Water–n-Decane Reverse Micelles

Computer simulation of pyridine, pyridine-2-ol, and pyridine-2,5-diol solubilization by Span 80–water reverse micelles in n-decane has been performed. All solubilized compounds are polar (their polarity increases in a series pyridine, pyridine-2,5-diol, and pyridine-2-ol) and have different numbers of donors/acceptors forming hydrogen bonds. The most probable positions of pyridine molecules relative to a reverse micelle change fundamentally with a rise in the number of hydroxyl groups in their structure. Pyridine, pyridine-2-ol, and pyridine-2,5-diol are located in the nonpolar medium, on the micelle surface between the head groups of surfactant molecules, and on the inside surface of the aqueous core, respectively. Thus, the number and arrangement of hydrophilic groups in the structure of a molecule, rather than its polarity, have the strongest effect on the ability to solubilization in the reverse micelles.

AOT reverse micelles as versatile reaction media for chitosan nanoparticles synthesis

It is known that Chitosan (Ch) can be used in several applications, such as antimicrobial agent or as drug delivery agent. However, being its water dispersibility very low at physiological pH it is necessary to find a way to improve it. One attractive strategy is to synthesize Chitosan Nanoparticles (Ch-NPs). In this work, a versatile method to obtain Ch-NPs with different and controlled sizes, that were successfully prepared by cross-linking reaction of glutaraldehyde and native chitosan inside of n-heptane/sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT)/water reverse micelles (RMs) is presented. Highly monodisperse NPs were synthesized as confirmed by Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM) techniques. The particle size was dependent on the reactants concentration, cross-linking degree and mainly the amount of water inside of the AOT RMs used as nanoreactors. While the cross-linking is quite difficult to control in bulk water, the reaction inside the RMs is more manageable and efficient.

The Use of AOBH‐DEHP Molecular Probe to Characterize BHDC Reverse Micelles Interfaces. Insights on the Interfacial Water Structure

AbstractThis work presents the use of the molecular probe: 3,6‐bis(dimethylamino) acridinium bis‐(2‐ethylhexyl) phosphate salt, AOBH‐DEHP. This probe is used to gain insights into the properties of the benzene/benzyl‐n‐hexadecyldimethylammonium chloride (BHDC)/water reverse micelles (RMs) interfaces. The techniques employed were absorption and emission spectroscopy in addition to the steady‐state and, time‐resolved fluorescence emission.For BHDC RMs without water addition, AOBH‐DEHP can be used to determine the critical micellar concentration, CMC. Upon addition of water, we detect, at concentrations of BHDC lower &lt; 1x10−2 M, a proton transfer process from the AOBH+ cation to the DEHP− anion producing AOB species. However, for [BHDC] &gt; 10−2 M, when the RMs is completely formed this process is reverted because water molecules at the interface interact with the cationic polar head of BHDC through the oxygen non‐bonding electron pair enhancing their hydrogen bond ability and acidity, hence it can easily transfer a proton to AOB species to form AOBH+.

On the design of a versatile ionic liquid, AOBH-DEHP, which can be used as a new molecular probe to investigate supramolecular assemblies

The motivation of our work is to find an exciting new molecular probe, which has the advantages that contains the acridine orange moiety but also has an ample range of solubility in different media. The probe is obtained through the acid-base reaction between acridine orange base (AOB) and bis-(2-ethylhexyl) phosphoric acid (HDEHP) giving AOBH-DEHP. This synthesized dye results to be a protic ionic liquid, since it is a viscous liquid at room temperature and, it is only constituted by ions.The spectroscopic behavior of AOBH-DEHP in homogeneous medium, using water, benzene and n-heptane as solvents and, in benzene or n-heptane/sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT)/water reverse micelles (RMs) has been investigated. Absorption, emission and single photon counting techniques, were used to fully characterize the new molecule in different environments.It is shown that AOBH-DEHP has all the advantages of its chromophore, AOBH+ but, the presence of the hydrophobic anion, DEHP−, gives to the dye, unique solubility in solvents of very different polarities. As such and, in contrast to AOBH+ chloride salts, AOBH-DEHP can be used to determine different properties, such as micropolarity, restricted motion environment, critical micellar concentration in different RMs media.

Synthesis, spectroscopic properties and photodynamic activity of two cationic BODIPY derivatives with application in the photoinactivation of microorganisms

Two cationic BODIPYs 3 and 4 were synthesized by acid-catalyzed condensation of the corresponding pyrrole and benzaldehyde, followed by complexation with boron and methylation. Compound 3 contains methyl at the 1,3,5 and 7 positions of the s-indacene ring and a N,N,N-trimethylamino group attached to the phenylene unit, while 4 is not substituted by methyl groups and the cationic group is bound by an aliphatic spacer. UV-visible absorption spectra of these BODIPYs show an intense band at ∼500 nm in solvents of different polarities and n-heptane/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/water reverse micelles. Compound 3 exhibits a higher fluorescence quantum yield (ΦF = 0.29) than 4 (ΦF = 0.030) in N,N-dimethylformamide (DMF) due to sterically hindered rotation of the phenylene ring. BODIPYs 3 and 4 induce photosensitized oxidation of 1,3-diphenylisobenzofuran (DPBF) with yields of singlet molecular oxygen of 0.07 and 0.03, respectively. However, the photodynamic activity increases in a microheterogenic medium formed by AOT micelles. Also, both BODIPYs sensitize the photodecomposition of l-tryptophan (Trp). In presence of diazabicyclo[2.2.2]octane (DABCO) or D-mannitol, a reduction in the photooxidation of Trp was found, indicating a contribution of type I photoprocess. Moreover, the addition of KI produces fluorescence quenching of BODIPYs and reduces the photooxidation of DPBF. In contrast, this inorganic salt increases the photoinduced decomposition of Trp, possibly due to the formation of reactive iodine species. The effect of KI was also observed in the potentiation of the photoinactivation of microorganisms. Therefore, the presence of KI could increase the decomposition of biomolecules induced by these BODIPYs in a biological media, leading to a higher cell photoinactivation.

Determination of Critical Micelle Concentrations of Surfactants by Terahertz Time-Domain Spectroscopy

A novel detection method is presented to determine the critical micelle concentrations (CMCs) of surfactants by using a simple and convenient terahertz time-domain spectroscopy (THz-TDS) technology which has been successfully used to study the picosecond dynamics of water in reverse micelles. Absorption coefficients or refractive indices of aqueous solutions of an ionic surfactant sodium dodecyl sulfate and a nonionic surfactant nonaethylene glycol monododecyl ether in 0.2–1.8 THz frequency range at different concentrations are measured through the THz-TDS. A clear intersection of THz absorption coefficient or refractive index caused by the micelle formation is observed. This phenomenon is strongly associated with the change of component ratio between surfactant, bulk water and hydration water during the formation of micelles. The corresponding concentration is determined as the CMC of the surfactant which is in good agreement with the most existing results using traditional methods. For comparison, absorption coefficients of the two surfactants in hydrochloric acid solutions are also measured and differences in contrast to those in aqueous solutions are observed and explained. Our findings indicate that THz spectroscopy technology can be applied to determine the CMCs of surfactants in a sensitive, accurate, and label-free way.

Synthesis, spectroscopic properties and photodynamic activity of a fulleropyrrolidine bearing a basic amino group and its dicationic analog against Staphylococcus aureus

Abstract N-Methyl-2-[4-(3-N,N-dimethylaminopropoxy)phenyl]fulleropyrrolidine (MPC60) was synthesized by 1,3-dipolar cycloaddition reaction of 4-(3-N,N-dimethylaminopropoxy)benzaldehyde, N-methylglycine and fullerene C60 in 43% yield. The amine groups of MPC60 were methylated with dimethyl sulfate to obtain a dicationic fullerene DPC602+ in 96 % yield. Absorption spectra of these fullerenes in N,N-dimethylformamide (DMF) and toluene/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/water reverse micelles showed strong absorptions in the UV region, with a peak at 430 nm and broader range of absorption up to 710 nm. Fluorescence quantum yields of about 10−4 were calculated for these compounds in DMF. A higher singlet molecular oxygen, O2(1Δg), generation was found for MPC60 than DPC602+ in DMF. The photodynamic activity of these photosensitizers remained high in a simple biomimetic AOT system. Also, the formation of superoxide anion radical induced by MPC60 and DPC602+ was detected in presence of NADH. Decomposition of l -tryptophan in DMF mediated by both fullerenes indicated a possible contribution of type I photoprocess. Photosensitized inactivation of Staphylococcus aureus was investigated using different conditions. Cell suspensions of 108 cells/mL incubated with 0.5 μM fullerene and irradiated for 30 min exhibited a 4.4 and 5.0 log decrease of cell survival by MPC60 and DPC602+, respectively. Therefore, these fullerene derivatives can be used as effective photosensitizers for the photodynamic inactivation of S. aureus cells.

Confined Space, Structural Biology, Biophysics and Drug Discovery

High-resolution multi-dimensional solution NMR is unique as a biophysical and biochemical tool in its ability to examine both the structure and dynamics of macromolecules at atomic resolution. Conventional non-TROSY/deuteration solution NMR approaches, however, are largely limited to examinations of relatively small (< 25 kDa) molecules, mostly due to the spectroscopic consequences of slow rotational diffusion. Encapsulation of macromolecules within the protective nanoscale aqueous interior of reverse micelles dissolved in low viscosity fluids has been developed as a means through which the ‘slow tumbling problem’ can be overcome. This approach has been successfully applied to diverse proteins and nucleic acids ranging up to 100 kDa, considerably widening the range of biological macromolecules to which the comprehensive small protein solution NMR methodologies can be applied. Recently, we have expanded the library of surfactants used to encapsulate proteins and nucleic acids within the reverse micelle water core with high structural fidelity. In addition, new applications have emerged including studies of protein hydration, dynamic nuclear polarization in solution, structural characterization of integral membrane proteins and membrane-anchored lipidated proteins. The nanoscale interior of the reverse micelle water core also offers the potential for a range of novel applications in drug discovery. With the emergence of fragment based drug discovery, the screening of protein targets for binding to weak ligands has become the focus of some interest. NMR is well positioned to provide detailed site-specific information about ligand binding to proteins. The confined space of the reverse micelle allows a considerable reduction in ligand required for detection of weak binding and can also significantly extend the detection sensitivity into the low mM regime. Examples utilizing dihydrofolate reductase and aldoketoreductase will be presented. Supported by NIH grants R01 GM107829, T32 GM071339, T32 GM008275, F32 GM087099 and NSF grant MCB-115803.

Synthesis, spectroscopic properties and photodynamic activity of porphyrin–fullerene C60 dyads with application in the photodynamic inactivation of Staphylococcus aureus

A covalently linked porphyrin–fullerene C60 dyad 5 was synthesized by 1,3-dipolar cycloaddition using 5-(4-formylphenyl)-10,15,20-tris[3-(N-ethylcarbazoyl)]porphyrin, N-methylglycine and fullerene C60. Methylation of 5 was used to obtain a cationic dyad 6. Spectroscopic properties were compared in toluene, N,N-dimethylformamide (DMF) and toluene/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/water reverse micelles. Absorption spectra of the dyads were essentially a superposition of the spectra of the porphyrin and fullerene reference compounds, indicating a very weak interaction between the chromophores in the ground state. The fluorescence emission of the porphyrin moiety in the dyads was strongly quenched by the attached fullerene C60 unit. The singlet molecular oxygen, O2(1Δg), productions (ΦΔ) were strongly dependent on the solvent polarity. Similar ΦΔ values were obtained for 5,10,15,20-tetrakis[3-(N-ethylcarbazoyl)]porphyrin (TCP) in both solvents. Also, dyad 5 showed a high O2(1Δg) generation in toluene. However, O2(1Δg) production mediated by 5 considerably diminished in the more polar solvent DMF. Also, a high photodynamic activity involving O2(1Δg) was found for both dyads in a simple biomimetic system formed by AOT reverse micelles. The photoinactivation ability of these dyads was investigated in Staphylococcus aureus cell suspensions. Photosensitized inactivation of S. aureus by dyad 6 exhibits a 4.5 log decrease of cell survival (99.997% cell inactivation), when the cultures are treated with 5 μM photosensitizer and irradiated with visible light (350–800 nm) for 30 min. Under these conditions, a lower photocytotoxic effect was found for 5 (3.2 log decrease). Furthermore, photoinactivation induced by 6 was higher than those obtained with the separate moieties of the dyad. Therefore, molecular structures formed by porphyrin–fullerene C60 dyads represent interesting photosensitizers to inactivate S. aureus.

The use of two non-toxic lipophilic oils to generate environmentally friendly anionic reverse micelles without cosurfactant. Comparison with the behavior found for traditional organic non-polar solvents

In this work two different non-toxic solvents/sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT)/water reverse micelles (RMs) have been investigated by dynamic (DLS) and static (SLS) light scattering techniques. Methyl laurate (ML) and isopropyl myristate (IPM) were used as external non-polar solvents to formulate the AOT RMs without cosurfactant. DLS results reveal the formation of IPM and ML AOT RMs containing water as a polar component since the droplet sizes values increase as the W0 values increase. To the best of our knowledge this is the first report where ML is used to formulate AOT RMs. The droplets size values, the maximum amount of water solubilized and the aggregation numbers (Nagg, determined by SLS) of both AOT RMs are dissimilar considering the chemical structure of the external solvents and they can be explained taking into account the different non-polar solvent penetration to the interface. The results suggest that IPM penetrate more the interface than ML in AOT RMs, diminishing the interdroplets interactions and producing RMs with smaller sizes and Nagg than ML/AOT. The higher viscosity and polarity of IPM in comparison with ML promotes the interface penetration. Thus, the penetration of IPM into the interface is higher than ML, making the interface of IPM/AOT RMs more rigid and, in consequence with smaller droplets sizes values. Finally, a peculiar comparable behavior (droplets size, maximum amount of water solubilized and Nagg) between n-heptane and ML AOT RMs and benzene and IPM AOT RMs was observed. These results present a very promissory field since that the unique properties of the alkanes/AOT/water RMs can be obtained using non-toxic lipophilic oils and, in the same way the opportunity to formulate environmentally friendly AOT RMs.

Measurement and Control of pH in the Aqueous Interior of Reverse Micelles

The encapsulation of proteins and nucleic acids within the nanoscale water core of reverse micelles has been used for over 3 decades as a vehicle for a wide range of investigations including enzymology, the physical chemistry of confined spaces, protein and nucleic acid structural biology, and drug development and delivery. Unfortunately, the static and dynamical aspects of the distribution of water in solutions of reverse micelles complicate the measurement and interpretation of fundamental parameters such as pH. This is a severe disadvantage in the context of (bio)chemical reactions and protein structure and function, which are generally highly sensitive to pH. There is a need to more fully characterize and control the effective pH of the reverse micelle water core. The buffering effect of titratable head groups of the reverse micelle surfactants is found to often be the dominant variable defining the pH of the water core. Methods for measuring the pH of the reverse micelle aqueous interior using one-dimensional 1H and two-dimensional heteronuclear NMR spectroscopy are described. Strategies for setting the effective pH of the reverse micelle water core are demonstrated. The exquisite sensitivity of encapsulated proteins to the surfactant, water content, and pH of the reverse micelle is also addressed. These results highlight the importance of assessing the structural fidelity of the encapsulated protein using multidimensional NMR before embarking upon a detailed structural and biophysical characterization.

Study on intramolecular charge transfer processes, solvation dynamics and rotational relaxation of coumarin 490 in reverse micelles of cationic gemini surfactant

The steady-state fluorescence properties, steady-state fluorescence anisotropy, solvation dynamics and rotational relaxation of coumarin 490 (C-490) have been studied in cationic gemini surfactant 1,4-bis(dodecyl-N,N-dimethylammoniumbromide)butane (12-4-12)–cyclohexane–n-pentanol–water reverse micelles (RMs). C-490 molecule resides in the water pool of RMs. A lesser extent of hydrogen bonding interactions occurs between the –OH group of the alcohol and the C-490 molecule at the interface of the present RMs as compared to the RMs of reported conventional cationic surfactants. The effect of the more hydrophobic nature of coumarin 480 (C-480) used to study the RMs of conventional cationic surfactants cannot be ruled out. C-490 migrates to the water pool with increasing content of water molecules. Therefore, the results of steady-state fluorescence properties, rotational relaxation and solvation dynamics depend on the water loading of RMs, unlike the RMs of conventional cationic surfactants. Thus, the solvation dynamics in gemini surfactant RMs are one order of magnitude faster as compared to the RMs of conventional cationic surfactants. The faster solvation dynamics in gemini surfactant RMs as compared with the reported AOT RMs are due to the absence of hydrogen bonding interactions between the water molecules and quaternary ammonium headgroups of gemini surfactants. The polarity of the surrounding microenvironment is found to have very little effect on the rates of non-radiative processes in the water pool of gemini surfactant RMs. The rates of non-radiative processes in the present RMs are found to be higher than those in reported AOT RMs.