The aqueous environment in AOT and Triton X-100 (w/o) microemulsions probed by fluorescence

Andrade, Suzana M.; Costa, Sı́lvia M. B.

doi:10.1039/b201477g

Cited by 31 publications

(37 citation statements)

References 40 publications

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“…The state of solubilized water in the aqueous core of reverse microemulsions has been widely studied 26. 29, 36–38 In the AOT‐based reverse microemulsions, only a few initial water molecules are needed to solvate the interface, and the remaining water molecules are available to form water pools; but, in TX‐100 aqueous microemulsions, there is a higher demand for hydration water 38. It has been suggested that the inner core water molecules have a strong tendency to form a hydrogen‐bonded bridged structure between two adjacent OE groups 39.…”

Section: Resultsmentioning

confidence: 99%

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Structural Studies of 1‐Butyl‐3‐methylimidazolium Tetrafluoroborate/TX‐100/ p‐Xylene Ionic Liquid Microemulsions

Gao¹,

Zhang²,

Xu³

et al. 2006

ChemPhysChem

168

135

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The ionic liquid (IL) 1‐butyl‐3‐methylimidazolium tetrafluoroborate (bmimBF4) forms nonaqueous microemulsions with p‐xylene, with the aid of the nonionic surfactant TX‐100. The phase behavior of the ternary system is investigated, and three microregions of the microemulsions—ionic liquid‐in‐oil (IL/O), bicontinuous, and oil‐in‐ionic liquid (O/IL)—are identified by conductivity measurements, according to percolation theory. On the basis of a phase diagram, a series of IL/O microemulsions are chosen and characterized by dynamic light scattering (DLS). The size of aggregates increases on increasing the amount of added polar component (bmimBF4), which is a similar phenomenon to that observed for typical water‐in‐oil (W/O) microemulsions, suggesting the formation of IL/O microemulsions. The microstructural characteristics of the microemulsions are investigated by FTIR and 1H NMR spectroscopy. The results indicate that the interaction between the electronegative oxygen atoms of the oxyethylene (OE) units in TX‐100 and the electropositive imidazolium ring may be the driving force for the solubilization of bmimBF4 into the core of the TX‐100 aggregates. In addition, the micropolarity of the microemulsions is investigated by using methyl orange (MO) as a UV/Vis spectroscopic probe. A relatively constant polarity of the microemulsion droplets is obtained in the IL microemulsion. Finally, a plausible structure for the IL/O microemulsion is presented.

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Section: Resultsmentioning

confidence: 99%

“…[38] It has been suggested that the inner core water molecules have a strong tendency to form a hydrogenbonded bridged structure between two adjacent OE groups. [39] An oblate form is observed in the TX-100 aqueous microemulsion, due to the longer size of the hydrophilic groups of TX-100.…”

Section: Possible Structure Of the Il/o Microemulsionmentioning

confidence: 99%

Structural Studies of 1‐Butyl‐3‐methylimidazolium Tetrafluoroborate/TX‐100/ p‐Xylene Ionic Liquid Microemulsions

Gao¹,

Zhang²,

Xu³

et al. 2006

ChemPhysChem

168

135

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“…Previously, Andrade et al have observed a Lewis base character of TX-100 in the interaction with another dye, acridine orange. 48 In the present case also, it is possible that TX-100 acts as a Lewis base toward 7H4MC, and thus, a part of the dye molecules form a kind of contact ion pair (7H4MC δ-/TX-100 δ+ , I) at the interfacial region, which absorbs in the longer-wavelength region (∼370 nm). Such an ion pair formation with a corresponding absorption band in the longer-wavelength region has also been reported for 7H4MC dye with the bases like triethyl amine in some nonhydroxylic solvents.…”

Section: Absorption and Fluorescence Spectral Features And Time-resolmentioning

confidence: 97%

Modulation of Excited-State Proton-Transfer Reactions of 7-Hydroxy-4-methylcoumarin in Ionic and Nonionic Reverse Micelles

Choudhury

Pal

2009

J. Phys. Chem. B

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The prototropic behavior of the dye, 7-hydroxy-4-methylcoumarin (7H4MC), has been studied in cationic benzyldimethylhexadecylammonium chloride (BDHC) and nonionic poly(oxyethylene)(tetramethylbutyl)phenyl ether (TritonX-100, TX-100) reverse micelles using ground-state absorption and steady-state and time-resolved fluorescence measurements. The results have been compared with the previous results in the anionic sodium 1,4-bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles. Although the probe dye, 7H4MC, is indicated to reside in the interfacial region in all of the reverse micelles studied, significant differences have been observed in the evolution of the different prototropic species. In BDHC reverse micelles, the anionic form is favored over the tautomeric form at the higher w0 values, which is contrary to the observation in AOT reverse micelles where both of these forms are almost equally produced. The higher propensity for the formation of the anionic form in BDHC reverse micelles has been explained on the basis of the additional electrostatic stabilization of the anionic species in the cationic BDHC reverse micelles compared to that in the anionic AOT reverse micelles. On the other hand, in TX-100 reverse micelles, the anionic form is not very evident, but interestingly, the tautomer form begins to appear beyond w0=2. The appearance of the tautomeric species apparently coincides with the formation of the water pool in the TX-100 reverse micelles. However, due to the more restricted nature of the water molecules within this reverse micelle (mostly dispersed around the oxyethylene chains), deprotonation of the 7H4MC dye and the consequential stabilization of the anionic form are considerably reduced. The results clearly reveal that the aqueous environment in the vicinity of the probe is quite different for the reverse micelles considered, and these differences largely modulate the prototropic processes of the excited dye.

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“…To estimate the maximum number of heparin chains within a CPC-GAG cluster, the hydrodynamic volume of the cluster was assumed to be of (19,54). spherical shape (V h ¼ 4=3pR 3 h ) and was divided by the volume of a single heparin chain saturated with the defined number of ligands as measured by ITC.…”

Section: Dynamic Light Scatteringmentioning

confidence: 99%

Binding and Clustering of Glycosaminoglycans: A Common Property of Mono- and Multivalent Cell-Penetrating Compounds

Ziegler

Seelig

2008

Biophysical Journal

114

109

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Recent observations in cell culture provide evidence that negatively charged glycosaminoglycans (GAGs) at the surface of biological cells bind cationic cell-penetrating compounds (CPCs) and cluster during CPC binding, thereby contributing to their endocytotic uptake. The GAG binding and clustering occur in the low-micromolar concentration range and suggest a tight interaction between GAGs and CPCs, although the relation between binding affinity and specificity of this interaction remains to be investigated. We therefore measured the GAG binding and clustering of various mono- and multivalent CPCs such as DNA transfection vectors (polyethylenimine; 1,2-dioleoyl-3-trimethylammonium-propane), amino acid homopolymers (oligoarginine; oligolysine), and cell-penetrating peptides (Penetratin; HIV-1 Tat) by means of isothermal titration calorimetry and dynamic light scattering. We find that these structurally diverse CPCs share the property of GAG binding and clustering. The binding is very tight (microscopic dissociation constants between 0.34 and 1.34 microM) and thus biologically relevant. The hydrodynamic radius of the resulting aggregates ranges from 78 nm to 586 nm, suggesting that they consist of numerous GAG chains cross-linked by CPCs. Likewise, the membrane-permeant monovalent cation acridine orange leads to GAG binding and clustering, in contrast to its membrane-impermeant structural analogs propidium iodide and ethidium bromide. Because the binding and clustering of GAGs were found to be a common denominator of all CPCs tested, these properties might be helpful to identify further CPCs.

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The aqueous environment in AOT and Triton X-100 (w/o) microemulsions probed by fluorescence

Cited by 31 publications

References 40 publications

Structural Studies of 1‐Butyl‐3‐methylimidazolium Tetrafluoroborate/TX‐100/ p‐Xylene Ionic Liquid Microemulsions

Structural Studies of 1‐Butyl‐3‐methylimidazolium Tetrafluoroborate/TX‐100/ p‐Xylene Ionic Liquid Microemulsions

Modulation of Excited-State Proton-Transfer Reactions of 7-Hydroxy-4-methylcoumarin in Ionic and Nonionic Reverse Micelles

Binding and Clustering of Glycosaminoglycans: A Common Property of Mono- and Multivalent Cell-Penetrating Compounds

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