Observation of Three Behaviors in Confined Liquid Water within a Nanopool Hosting Proton-Transfer Reactions

Douhal, Abderrazzak; Angulo, Gonzalo; Gil, Michał; Organero, Juan Ángel; Sanz, Mikel; Tormo, Laura

doi:10.1021/jp068764+

Cited by 63 publications

(74 citation statements)

References 48 publications

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“…Water dynamics can be investigated using nuclear magnetic resonance (NMR) (Grigolini and Maestro 1986;Quist and Halle 1988), fluorescence spectroscopy Douhal et al 2007;Pant et al 1998;Ueda and Schelly 1989;Zinsli 1979), dielectric relaxation (Nandi et al 2000) and ultrafast IR spectroscopy (Cringus et al 2007;Piletic et al 2005;Tan et al 2005a,b). Neutron scattering also provides information that can be directly compared to molecular simulation results, specifically those focused on the diffusion of interfacial water (Cummings et al 2010;Harpham et al 2004;Mamontov and Cole 2006).…”

Section: Experimental Toolsmentioning

confidence: 99%

“…Because this technique is responsive only to inhomogeneous structures, vibrational sum frequency spectroscopy can provide important insights into the dynamic behaviour of water at interfaces (Du et al 1993;Scatena et al 2001). For example, Salmeron and co-workers used this technique to study the properties of hydration water on mica at room conditions as a function of the amount of water present on the surface (Xu et al 1998).…”

Section: Vibrational Sum Frequency Generationmentioning

confidence: 99%

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From Interfacial Water to Macroscopic Observables: A Review

Striolo

2011

Adsorption Science & Technology

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ABSTRACT:The scientific community has always been fascinated by the properties of water and, consequently, a number of investigations continue to address this ubiquitous fluid responsible for life on this planet. Interfacial water plays an important role in a number of physical phenomena that include proteinfolding, structure/function relationships in enzymes, the design of nano-fluidic devices, and even macroscopic effects including drag reduction. Interfacial water is attracting renewed interest because of applications such as electrical double layer capacitors, and also for the microbial conversion of cellulose to biofuels. Current scientific explorations regarding interfacial water take advantage of innovations in experimental capabilities, theoretical models and computational tools. Particular attention has been devoted recently to uncovering the relationships between macroscopic properties, often summarized under the hydrophobic/hydrophilic characterization of solid surfaces, to the atomic-level behaviour of water near interfaces. The goal of the present review is to compile recent results obtained along these research objectives, for the most part obtained by simulation studies, to discuss some experimental techniques that appear most adequate to validate the simulation results (specular X-ray reflectivity, ultrafast IR spectroscopy, atomic force microscopy, and others), and to propose possible research topics to further develop this field. Because of our recent interests, the surfaces considered herein are mainly oxides.

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Section: Experimental Toolsmentioning

confidence: 99%

Section: Vibrational Sum Frequency Generationmentioning

confidence: 99%

From Interfacial Water to Macroscopic Observables: A Review

Striolo

2011

Adsorption Science & Technology

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“…5,6 Reverse micelles formed by surfactant molecules in hydrocarbon solvents with their polar head groups pointing inward can be good candidates for mimicking such nanoreactors. [7][8][9] The reverse micelle is nothing but nanometersized droplets of water or polar solvent, surrounded by a layer made of surfactant molecule and immersed in a nonpolar solvent. Though the ground-and excited-state proton transfer (PT) reactions have extensively been studied in the microheterogeneous environment of reverse micelles, [9][10][11][12][13][14] the acidity of surfactant bound water, the particular nature of the confined water, and its influence on PT are not yet completely understood.…”

Section: Introductionmentioning

confidence: 99%

Nanopools Governing Proton Transfer in Diametrical Ways in the Ground and Excited State

et al. 2008

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We present here the effects of geometrically constrained environments on the proton transfer reaction of 4-methyl 2,6-diformyl phenol (MFOH) both in the ground and excited states by employing steady-state and time-resolved fluorescence spectroscopy having picosecond and femtosecond resolutions. The nanometer-sized water pools formed in the ternary microemulsion of n-heptane-aerosol OT-water promote reprotonation of the probe. As we go on increasing the water content up to a certain value in the ground state whereas deprotonation is favored in the excited state. The emission intensity has a complex behavior as the water content is changed in the system. The lower fluidity of confined water within the reverse micelle with respect to the normal bulk water alters the related dynamics of the H-bonded network. These observations are rationalized on the basis of altered ionic water activity in the confined surroundings, i.e., on dielectric constant, ionic mobility, pH, and the favorable orientation of dipoles in the medium. Our observations might be helpful to infer about the characteristics of nanoreactors, which often mimic many biological hydrophilic pockets.

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“…[5][6][7][8][9][10][11][12][13] For example, the dielectric constant of a water nanopool has been reported to be much lower than that of bulk water (ε = 78. 5) 17 but similar to that of an alcohol (ε = [30][31][32][33][34][35][36][37][38][39][40].…”

Section: -16mentioning

confidence: 99%

“…As already mentioned above, the confinement effect and the enclosing interfacial surfaces of water nanopools are the major factors to determine the properties, such as H-bonding ability, polarity, and viscosity, of waterpools. [5][6][7][8][9][10][11][12][13] Water nanopools of AOT reverse micelles have been suggested to be alcohollike in polarity; water confined in reverse micelles has a relative dielectric constant (ε) of 30-40, which is very close to ε of methanol (33) and much smaller than ε of bulk water (78). [17][18][19] Thus, the micropolarity of water near 6HQ in reverse micelles is substantially low compared with the polarity of bulk water.…”

Section: Notesmentioning

confidence: 99%

Anomalous Acid-Base Equilibria in Biologically Relevant Water Nanopools

Park

Yoo²,

Pyo³

et al. 2012

Bulletin of the Korean Chemical Society

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Water plays a crucial role in many principal biological phenomena such as enzymatic catalysis and proton pumping through a membrane protein channel.1-4 Moreover, in biological systems, water is usually contained in a small pocket of a membrane, 5-8 and such confined water, which is generally called a water nanopool, [8][9][10] shows peculiar properties differing considerably from the properties of bulk water. 8-16The confinement effect and the enclosing interfacial surfaces of waterpools are the main factors to determine the properties, such as polarity, viscosity, and H-bonding ability, of water nanopools.5-13 For example, the dielectric constant of a water nanopool has been reported to be much lower than that of bulk water (ε = 78.5)17 but similar to that of an alcohol (ε = 30-40).18,19 On the other hand, biological processes often take place based on proton relay along a hydrogen (H)-bonded chain, [1][2][3][4][20][21][22][23][24] and the dynamics of biological proton relay is determined by the size, the structure, and the motion of a water cluster which is the prime agent in most of biological systems. 3,[13][14][15][24][25][26] Thus, for better understanding of cellular dynamics, it is necessary to investigate the properties of a biologically relevant water nanopool as a biomimetic system of water confined in a cell membrane. In this regard, water nanopools confined in reverse micelles, which are formed by surfactant molecules having polar headgroups pointing inward and dispersed in hydrocarbon solvents, can be good model systems of biological water. 6,18,19,27 It is a unique feature of reverse micelles that they can make nonpolar media to solubilize a large amount of water by encapsulating water molecules in their inner polar cores; 28 reverse micelles are surrounded by a layer of surfactant molecules such as Aerosol-OT (sodium 1,4-bis-2-ethylhexylsulfosuccinate, AOT) and immersed in a nonpolar solvent, so that nanometer-sized droplets of a polar solvent such as water are formed inside. The polar headgroups of surfactant molecules point inward toward a polar solvent pool, and the alkyl chains of the surfactant molecules point outward toward a nonpolar solvent. About 20 surfactant molecules of AOT form a reverse micelle having a diameter of 3.0 nm above the critical concentration of 1 mM in a hydrocarbon solvent such as n-heptane.29 By adding water to the AOT solution, microemulsions of nanometer-sized water droplets surrounded by AOT molecules are formed, and the size of water nanopools confined in AOT reverse micelles increases as the concentration of water increases. In n-heptane, the diameters in nanometers of the waterpools have been reported to be about 0.3w 0 , in which w 0 is the molar ratio of water to AOT. 30The catalytic properties of water nanopools depend strongly on the hydration extent of reverse micelles and on the solvation structure of reactants relevant to the polarity of waterpools confined in reverse micelles. [5][6][7][8]17,18 The peculiar structure of waterpools contained in reverse mi...

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Observation of Three Behaviors in Confined Liquid Water within a Nanopool Hosting Proton-Transfer Reactions

Cited by 63 publications

References 48 publications

From Interfacial Water to Macroscopic Observables: A Review

From Interfacial Water to Macroscopic Observables: A Review

Nanopools Governing Proton Transfer in Diametrical Ways in the Ground and Excited State

Anomalous Acid-Base Equilibria in Biologically Relevant Water Nanopools

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