Water Immobilization at Surfactant Interfaces in Reverse Micelles

Riter, Ruth E.; Willard, Dale M.; Levinger, Nancy E.

doi:10.1021/jp973330n

Cited by 308 publications

(552 citation statements)

References 85 publications

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“…[15][16][17][18][19] Mid-infrared ultrafast pumpprobe spectroscopy of RMs of different well-defined sizes revealed slow vibrational relaxation dynamics of water at the interface. 16 Using the picosecond-resolved fluorescence spec-…”

Section: Introductionmentioning

confidence: 99%

Validation and Divergence of the Activation Energy Barrier Crossing Transition at the AOT/Lecithin Reverse Micellar Interface

et al. 2008

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In this report, the validity and divergence of the activation energy barrier crossing model for the bound to free type water transition at the interface of the AOT/lecithin mixed reverse micelle (RM) has been investigated for the first time in a wide range of temperatures by time-resolved solvation of fluorophores. Here, picosecondresolved solvation dynamics of two fluorescent probes, ANS (1-anilino-8-naphthalenesulfonic acid, ammonium salt) and Coumarin 500 (C-500), in the mixed RM have been carefully examined at 293, 313, 328, and 343 K. Using the dynamic light scattering (DLS) technique, the size of the mixed RMs at different temperatures was found to have an insignificant change. The solvation process at the reverse micellar interface has been found to be the activation energy barrier crossing type, in which interface-bound type water molecules get converted into free type water molecules. The activation energies, E a , calculated for ANS and C-500 are 7.4 and 3.9 kcal mol -1 , respectively, which are in good agreement with that obtained by molecular dynamics simulation studies. However, deviation from the regular Arrhenius type behavior was observed for ANS around 343 K, which has been attributed to the spatial heterogeneity of the probe environments. Time-resolved fluorescence anisotropy decay of the probes has indicated the existence of the dyes in a range of locations in RM. With the increase in temperature, the overall anisotropy decay becomes faster revealing the lability of the microenvironment at elevated temperatures.

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Section: Introductionmentioning

confidence: 99%

Validation and Divergence of the Activation Energy Barrier Crossing Transition at the AOT/Lecithin Reverse Micellar Interface

et al. 2008

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“…reverse micelles, carbon nanotubes, and glycolipid membranes) is characterized by a disrupted hydrogen bonding network and decreased solvent dynamics relative to its bulk properties. [31][32][33][34][35][36][37][38][39] Numerous studies have analyzed the dynamics of solvent molecules inside silica sol-gel pores. [40][41][42][43][44][45][46][47][48] Using small fluorescent molecules as environmental probes, several studies have reported small increases of the solvent viscosities in silica sol-gel pores.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Proteins Encapsulated in Silica Sol−Gel Glasses Studied with IR Vibrational Echo Spectroscopy

2006

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Spectrally-resolved infrared stimulated vibrational echo spectroscopy is used to measure the fast dynamics of heme-bound CO in carbonmonoxy-myoglobin (MbCO) and hemoglobin (HbCO) embedded in silica sol-gel glasses. On the time scale of ~100 fs to several ps, the vibrational dephasing of the heme-bound CO is measurably slower for both MbCO and HbCO relative to aqueous protein solutions. The fast structural dynamics of MbCO, as sensed by the heme-bound CO, are influenced more by the sol-gel environment than those of HbCO. Longer time scale structural dynamics (tens of ps), as measured by the extent of spectral diffusion, are the same for both proteins encapsulated in sol-gel glasses compared to aqueous solutions. A comparison of the sol-gel experimental results to viscosity dependent vibrational echo data taken on various mixtures of water and fructose shows that the sol-gel encapsulated MbCO exhibits dynamics that are the equivalent to the protein in a solution that is nearly 20 times more viscous than bulk water. In contrast, the HbCO dephasing in the sol-gel reflects only a 2-fold increase in viscosity. Attempts to alter the encapsulating pore size by varying the molar ratio of silane precursor to water (R-value) used to prepare the sol-gel glasses were found to have no effect on the fast or steady-state spectroscopic results. The vibrational echo data are discussed in the context of solvent confinement and protein-pore wall interactions to provide insights into the influence of a confined environment on the fast structural dynamics experienced by a biomolecule.

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“…46 Such measurements have been carried out by Levinger and co-workers in a wide variety of reverse micelles, [9][10][11][12][13][14][15] Bhattacharyya and co-workers in reverse micelles, vesicles, solgels, and zeolites, 4 -8 Baumann et al in sol-gels, 16,17 and a number of other groups. 18 -25 In paper I we found that a chromophore with a charge transfer transition in a hydrophobic spherical nanometer-scale cavity displays different trends in the steady-state absorption and fluorescence spectra with cavity size.…”

Section: Introductionmentioning

confidence: 99%

Simulations of time-dependent fluorescence in nano-confined solvents

Thompson

2004

The Journal of Chemical Physics

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The time-dependent fluorescence of a model diatomic molecule with a charge-transfer electronic transition in confined solvents has been simulated. The effect of confining the solvent is examined by comparing results for solutions contained within hydrophobic spherical cavities of varying size ͑radii of 10-20 Å͒. In previous work ͓J. Chem. Phys. 118, 6618 ͑2002͔͒ it was found that the solute position in the cavity critically affects the absorption and fluorescence spectra and their dependence on cavity size. Here we examine the effect of cavity size on the time-dependent fluorescence, a common experimental probe of solvent dynamics. The present results confirm a prediction that motion of the solute in the cavity after excitation can be important in the time-dependent fluorescence. The effects of solvent density are also considered. The results are discussed in the context of interpreting time-dependent fluorescence measurements of confined solvent systems.

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Water Immobilization at Surfactant Interfaces in Reverse Micelles

Cited by 308 publications

References 85 publications

Validation and Divergence of the Activation Energy Barrier Crossing Transition at the AOT/Lecithin Reverse Micellar Interface

Validation and Divergence of the Activation Energy Barrier Crossing Transition at the AOT/Lecithin Reverse Micellar Interface

Dynamics of Proteins Encapsulated in Silica Sol−Gel Glasses Studied with IR Vibrational Echo Spectroscopy

Simulations of time-dependent fluorescence in nano-confined solvents

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