Sodium Octyl Sulfate Research Articles

Self-Assembly in Mixtures of an Anionic and a Cationic Surfactant: A Comparison between Small-Angle Neutron Scattering and Cryo-Transmission Electron Microscopy

The self-assembly in SOS-rich mixtures of the anionic surfactant sodium octyl sulfate (SOS) and the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) has been investigated with the complementary techniques small-angle neutron scattering (SANS) and cryo-transmission electron microscopy (cryo-TEM). Both techniques confirm the simultaneous presence of open and closed bilayer structures in highly diluted samples as well as the existence of small globular and large elongated micelles at higher concentrations. However, the two techniques sometimes differ with respect to which type of aggregates is present in a particular sample. In particular, globular or wormlike micelles are sometimes observed with cryo-TEM in the vicinity of the micelle-to-bilayer transition, although only bilayers are present according to SANS and the samples appear bluish to the eye. A similar discrepancy has previously been reported but could not be satisfactorily rationalized. On the basis of our comparison between in situ (SANS) and ex situ (cryo-TEM) experimental techniques, we suggest that this discrepancy appears mainly as a result of the non-negligible amount of surfactant adsorbed at interfaces of the thin sample film created during the cryo-TEM specimen preparation. Moreover, from our detailed SANS data analysis, we are able to observe the unusually high amount of free surfactant monomers present in SOS-rich mixtures of SOS and CTAB, and the experimental results give excellent agreement with model calculations based on the Poisson-Boltzmann mean field theory. Our careful comparison between model calculations and experiments has enabled us to rationalize the dramatic microstructural transformations frequently observed upon simply diluting mixtures of an anionic and a cationic surfactant.

Enhanced recovery of spermatozoa and comprehensive lysis of epithelial cells from sexual assault samples having a low cell counts or aged up to one year

Differential extraction (DE) is the most common method for processing sexual assault samples, allowing for the simultaneous recovery of sperm and epithelial cells from the swab with the separation of sperm cells from epithelial cell DNA by exploiting the differences in the cell membrane susceptibility to detergents. However, sperm cell recovery when using DE is generally 40-50% [1], which can reduce the probability of obtaining a STR profile of the semen contributor, especially if the sample is aged or has a low number of sperm cells. Here, we present a novel buffer, containing SDS and ProK that, when used as an initial incubation buffer, enhances sperm cell recovery to as high as 90%, representing a 200-300% increase over conventional DE buffer. Adjusting the incubation time and temperature provided high, reproducible sperm cell yields. Sample vortexing and replacement of SDS with sodium octyl sulfate (SOS), another sulfate-based anionic detergent, did not provide any further enhancement of the sperm cell recoveries. Furthermore, the one-step buffer provided up to a 300% increase in recovery over the conventional DE buffer when used on samples aged up to one year. STR analysis of samples containing 500 or more sperm cells treated with this buffer showed comparable results (i.e., full STR profiles; 16 of 16 loci) to those obtained using a conventional DE buffer. Finally, when the sample contained only 400 sperm cells (recovered in 100μL volume, then extracted), substantially more STR loci (14 of 16) were generated using the novel buffer in comparison to the conventional DE buffer (4 of 16 loci). This work demonstrates that this buffer may be useful as an alternative for the initial sample incubation step in differential extraction, particularly for aged or samples known to have a low number of sperm cells.

An economic method for synthesis of highly ordered porous silica

We report an economic method for synthesis of highly ordered silica with a mixing surfactant system containing short-chain cationic surfactant (decyltrimethyl ammonium bromide, denoted C10TMAB) and short-chain anionic surfactant (sodium octyl sulfate, denoted SOS) as the templating agents. Highly ordered supermicroporous silica was synthesized by judiciously chosen mixing ratio of surfactants. The samples were characterized by small-angle X-ray diffraction, transmission electron microscopy, and N2 adsorption–desorption. The results showed that the pore structure of the resulting silica belongs to the two-dimensional hexagonal structure (space group 2D-p6mm) with a pore size of ca. 2.2nm. Moreover, the method proposed herein is expected to facilitate the synthesis of not only porous silicas but also materials with other framework compositions.

On the growth of pneumatic foams

This work reports on the behaviour of tenacious and transient pneumatic foams produced at large range of values of gas delivery rates (or superficial velocities) and surface tensions. Experimental data from the literature and produced in the course of this study were processed and analyzed. The tenacious foams were stabilized via Polyoxiethylene-2 sulfate (SDP(2)S) in presence of 0.024M NaCl and 0.003M AlCl(3) ( CMC = 1.83×10(-2) M) in the concentration range of 3.33×10(-3) M to 3.8×10(-2) M (0.18CMC -2.08CMC corresponding to values of the dynamic surface tension in the range of 42.7mN/m to 37.5mN/m. The range of gas delivery rates was from 20.5ml/min to 482.8ml/min. It was found out that the rate of foam generation coincides with the gas delivery rate until a certain critical value of the latter, beyond which the rate of foam growth exceeds the rate of gas delivery. The level of this exceeding depends on the dynamic surface tension. The lower the value of the dynamic surface tension the larger the level of this exceeding. This rule was found valid until a certain upper limit of the gas delivery rate, at which the dependence on the dynamic surface tension ceases to exist. The second set of experiments was conducted on transient foams. The latter were stabilized by three members of homologue surfactants series: sodium octylsulfate (SOS), sodium decylsulfate (SDeS), and sodium dodecylsulfate (SDS) in the concentration range of 0.01CMC -0.1CMC corresponding to 72.75mN/m to 68.18mN/m. The aqueous solutions of the three surfactant homologues had identical values of static surface tension at the same ratio C/CMC . Bikerman's "unit of foaminess" was measured for each particular case. It was shown that at identical equilibrium surface tensions both the foaminess and the rate of foam decay increase upon lengthening of the surfactant's hydrocarbon chain. It was indicated as well that the foaminess increases linearly upon raising the gas delivery rate until a certain critical value, above which substantial increase is observed. It was finally concluded that both the tenacious and the transient foams have completely different behaviour. For this reason they should be modeled separately but more experimental data are still needed.

Molecular dynamics simulation of cetyltrimethylammonium bromide and sodium octyl sulfate mixtures: aggregate shape and local surfactant distribution

To examine the self-assembly of cationic-anionic (catanionic) surfactant mixtures, we performed molecular dynamical (MD) simulations at fixed surfactant numbers but different ratios of cationic cetyltrimethylammonium bromide (CTAB) and anionic sodium octyl sulfate (SOS) aqueous mixtures, which were investigated previously (J. Phys. Chem. 1996, 100, 5874-5879). The simulation results show that with an increase of CTAB, there are two different potential aggregation evolving paths. For SOS-rich mixtures, the aggregation transition is sphere-disc-rod, while in CTAB-rich mixtures, it is rod-sphere. Furthermore, a disc micelle model was built to explain the shape of the aggregates with varying compositions of CTAB and SOS. In the model, the surfactant distribution in disc micelles is spontaneously adjusted according to the different curvature of the disc surface. The short-tailed SOS tends to stay in the edge region of high curvature, while in the disc center, where the curvature is very low, equimolar mixing of cationic and anionic surfactants is better for the arrangement of CTAB and SOS. Based on this model, the relation between the shape and composition of CTAB and SOS aggregates is well established by analyzing the local surfactant distribution. These new simulations on the evolving mechanism of aggregate shape are very important for the full understanding of the complex phase behavior in cationic and anionic mixtures and for the self-assembly of other mixed surfactant systems.

Structure, orientation and stability of lysozyme confined in layered materials

The confinement of lysozyme in 3 layered materials based on montmorillonite and lamellar double hydroxides exhibiting different surface charges was studied. The protein structure and orientation in these materials were determined by X-ray diffraction, time resolved fluorescence and fluorescence anisotropy. For montmorillonite exchanged with sodium and modified with a non-ionic surfactant (tri-ethylene glycol mono n-decyl ether), the lysozyme was found to be located in the interlayer space with the “end-on” and “side-on” orientations, respectively. Conversely, no lysozyme intercalation was observed with a lamellar double hydroxide modified with an anionic surfactant (sodium octylsulfate), since the protein was adsorbed on the surface of the particles. Fourier transformed infrared spectroscopy analysis shows that lysozyme confinement in the interlayer space preserves its structure after dehydration, whereas some structural changes were observed for lysozyme adsorbed on the particle surface.

Structural Analysis of Protein Denaturation with Alkyl Perfluorinated Sulfonates

The denaturation of three model proteins, bovine serum albumin (BSA), ovalbumin, and lysozyme, with fully fluorinated potassium sulfonate surfactants was studied using small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), polyacrylamide gel electrophoresis (PAGE), and circular dichroism (CD). Scattering analysis revealed that protein-surfactant complexes of fluorinated molecules could also organize into pearl-necklace structures. In contrast, fluorinated surfactants with just four carbons in the tail (PFC(4)S) promoted the formation of much larger aggregates. The changes in secondary structure of the protein-surfactant complexes were also analyzed by CD to determine the relative content of α-helix and β-sheet motifs. The CD spectra suggest that the α-helix content steadily decrease when proteins were denatured with surfactants of smaller tail lengths. Potassium perfluoro-octanesulfonate (PFC(8)S) was able to form stable complexes with all three of the model proteins, but lysozyme was unstable when denatured in the presence of shorter fluorinated surfactants. Finally, PFC(8)S was also found to be more effective in PAGE separations than a similarly sized hydrogenated surfactant, sodium octyl sulfate (SC(8)S), but fluorinated surfactants with only six (PFC(6)S) or four (PFC(4)S) carbons in the tail length showed much weaker performance in proteomic separations.

Foam production – Ratio between foaminess and rate of foam decay

Foams are usually characterized by the foaminess of their surfactant solutions and the rate of foam decay. These two properties have been described many times separately in the literature. There is a certain correlation between them, which can vary depending on the type and the concentration of the surfactants, the method of foam generation, etc. We suggest with this work a new parameter unifying foaminess and rate of foam decay. The foam production is a parameter, which is a ratio between foaminess and rate of foam decay. It was shown an example how foaminess, rate of foam decay and foam production depends on C/CMC (C – surfactant concentration, CMC – critical micelle concentration) of aqueous solutions of sodium octylsulfate (SOS). In addition, it has been stressed that a number of scientific problems on transient foams can be solved by means of the approach pointed out by this study. An example, for which the foam production depends on the way of foam generation, is given. A new criterion for assessing the ability of the surfactants to stabilize foams has been suggested. Thus, the stronger surfactants do not always produce more stable transient foams than the weaker ones, as usually is assumed.

Heterologous expression and characterization of a recombinant thermostable alkylsulfatase (sdsAP)

A novel alkylsulfatase gene, sdsAP, was cloned from a newly isolated bacterium Pseudomonas sp. S9. It encoded a protein of 675 amino acids with a calculated molecular mass of 74.9 kDa. The protein contained a typical N-terminal signal peptide of 41 amino acid residues, followed by a metallo-β-lactamase like domain at the N-terminus and a SCP-2-like domain at the C-terminus. This domain organization mode suggested that it belonged to the type III sulfatase. The mature alkylsulfatase was overexpressed in Escherichia coli. The optimal temperature and pH of the recombinant SdsAP were 70°C and 9.0, respectively. Notably, at optimal conditions, the purified recombinant SdsAP had a high specific activity of 23.25 μmol min(-1) mg(-1), a K(m (app)) of 264.3 μmol, and a V(max (app)) of 33.8 μmol min(-1) mg(-1) for SDS. Additionally, it still retained more than 90% activity after incubation at 65°C for 1 h, which was much different from other alkylsulfatases reported. The recombinant enzyme hydrolyzed the primary alkyl sulfate such as sodium octyl sulfate and sodium dodecyl sulfate (SDS). It was a Zn(2+)-containing and Ca(2+) activated alkylsulfatase. This is the first report to explore the various characteristics of the heterologous recombinant alkylsulfatase in details. These favorable properties could make SdsAP attractive to be useful in the degradation of SDS-containing waste.

Transgenic conversion of omega-6 into omega-3 fatty acids in a mouse model of Parkinson's disease

We have recently identified a neuroprotective role for omega-3 polyunsaturated fatty acids (n-3 PUFAs) in a toxin-induced mouse model of Parkinson's disease (PD). Combined with epidemiological data, these observations suggest that low n-3 PUFA intake is a modifiable environmental risk factor for PD. In order to strengthen these preclinical findings as prerequisite to clinical trials, we further investigated the neuroprotective role of n-3 PUFAs in Fat-1 mice, a transgenic model expressing an n-3 fatty acid desaturase converting n-6 PUFAs into n-3 PUFAs. Here, we report that the expression of the fat-1 transgene increased cortical n-3:n-6 PUFA ratio (+28%), but to a lesser extent than dietary supplementation (92%). Such a limited endogenous production of n-3 PUFAs in the Fat-1 mouse was insufficient to confer neuroprotection against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine neurotoxicity as assessed by dopamine levels, tyrosine hydroxylase (TH)-positive neurons and fibers, as well as nigral Nurr1 and dopamine transporter (DAT) mRNA expression. Nevertheless, higher cortical docosahexaenoic acid (DHA) concentrations were positively correlated with markers of nigral dopaminergic neurons such as the number of TH-positive cells, in addition to Nurr1 and DAT mRNA levels. These associations are consistent with the protective role of DHA in a mouse model of PD. Taken together, these data suggest that dietary intake of a preformed DHA supplement is more effective in reaching the brain and achieving neuroprotection in an animal model of PD.

Characterization and electrochemical investigations of micellar/drug interactions

The effect of adding surface-active agents to electrolytes containing isoniazid (INH), an antituberculous drug, on the voltammetric response of carbon paste electrode (CPE) was studied. The enhancement of current signal due to the oxidation process was a function of the amount of analyte, pH of the medium, surfactants’ type, and chain length and aromaticity and accumulation time at the electrode surface. Eight surfactants were used, three anionic type, sodium dodecyl sulphate (SDS), sodium octyl sulphate (SOS) and sodium dodecyl benzene sulphonate (SDBS), three cationic type, cetyl trimethyl ammonium bromide (CTAB), trimethyl octyl ammonium bromide (TMOB) and cetyl pyridinium bromide (CPB) and two nonionic surfactants, albumin and Triton X-405. Addition of SDS and SDBS to the isoniazid-containing electrolyte was found to enhance the oxidation current signals while SOS showed an opposite effect. The addition of either the cationic or nonionic surfactants was found to decrease oxidation current signals. To confirm the interactions between surfactant and isoniazid, absorbance spectroscopy has been performed. NMR measurements gave a good expectation for the location and orientation of INH in different micelles and gave a similar conclusion to that obtained from electrochemical and UV–vis data. The use of SDS in the electrochemical determination of isoniazid using differential pulse voltammetry at carbon paste electrode improved the limit of detection to 6.29ngmL−1. The validity of using this method in the determination of drug active ingredient in tablet formulations was also demonstrated.

Photophysics and dynamics of a β-carboline analogue in room temperature ionic liquids

Room temperature ionic liquids are rapidly emerging as a new class of media that are ideally suited for various applications including carrying out chemical reactions. In the present article, we report the photophysics of a β-carboline analogue, namely, 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine (AODIQ), in three room temperature ionic liquids (RTILs), 1-butyl-3-methylimidazolium methyl sulfate ([BMIM][MeSO(4)]), 1-butyl-3-methylimidazolium octyl sulfate ([BMIM][C(8)SO(4)]) and 1-ethyl-3-methylimidazolium methyl sulfate ([EMIM][MeSO(4)]). Out of these, [BMIM][C(8)SO(4)] is a typical RTIL that forms micellar aggregates above a critical micellar concentration (CMC). Steady state absorption, steady state and time resolved fluorescence techniques are used to probe the properties of these systems. The investigation reveals that the photophysics of AODIQ is modified significantly in the micelle-forming RTIL as compared to that in the other two. A comparative study with the fluorophore in [BMIM][C(8)SO(4)] and a conventional anionic surfactant of a similar hydrophobic chain length from the sodium-n-alkyl sulfate series, viz., sodium octyl sulfate (S(8)S), reveals that the fluorophore experiences a more constrained environment in the RTIL micelle as compared to the conventional anionic micelle.

Influence of Daphnia infochemicals on functional traits of Microcystis strains (Cyanobacteria)

We conducted a laboratory experiment to investigate the influence of Daphnia infochemicals on growth rate, microcystin production, colony formation and cell size of eight Microcystis strains isolated from two lakes. The strains were characterized genetically by their 16S-23S rDNA ITS sequence. The experiment was composed of four treatments: (1) a control using filtered WC medium, (2) addition of Scenedesmus obliquus culture medium filtrate, (3) addition of Daphnia magna culture medium filtrate and (4) addition of sodium octyl sulphate, a commercially available Daphnia infochemical. Our results showed that sympatric strains differed strongly for the measured functional traits, while no correlations between traits were found. Between-strain differences in growth rate, microcystin production, colony formation and cell size were generally larger than the differences in phenotypes observed between treatments. Despite this, several strains reacted to the infochemicals by changing functional trait values. Daphnia culture medium filtrate and, to a lesser extent, sodium octyl sulphate had a negative influence on the growth rate of half of the strains and stimulated microcystin production in one strain, but the latter effect was not Daphnia-specific as Scenedesmus culture medium filtrate had the same effect. Daphnia culture medium filtrate also induced colony formation in one strain. Our data suggest that Daphnia infochemicals generally have a weak influence on growth rate, microcystin production and colony formation of Microcystis strains as compared to the inter-strain variability, while existing inducible effects are highly strain-specific.

Determination of 1,1-dimethylhydrazine and its decomposition products using ion-pair chromatography

The influence of the nature of the ion-pair reagent (IPR) using sodium octylsulfate, octylsulfonate, and dodecylsulfate as an example on the separation of asymmetric dimethylhydrazine (ADMH) and its decomposition products has been investigated using a Synergi Hydro RP column. It has been shown that the use of sodium octylsulfate as an IRP is preferable. The approach to simultaneous determination of hydrazine, methylhydrazine, ADMH, N-nitrosodimethylamine, and tetramethyl-2-tetrazene with detection limits in water matrices of 0.3, 0.7, 0.8, 7, and 1.2 μg/L respectively (sample volume of 100 μL) has been proposed.

Quantitative analysis of valiolamine through pre-column derivatization with phenylisocyanate using high-performance liquid chromatography with UV detection: Selection of reagent, identification of derivative and optimization of derivatization conditions

This report describes the improved quantitative determination of valiolamine in a medium for microbial culture using high-performance liquid chromatography with UV detection. Valiolamine aqueous solution was dried, dissolved in dimethyl sulfoxide and derivatization performances of phenylisocyanate (PHI), 1-fluoro-2,4-dinitrobenznene and 1-naphthylisothiocyanate were compared in the presence of triethylamine. The PHI was chosen as the most suitable derivatization reagent and the valiolamine–PHI derivative was identified by thin-layer chromatography and electrospray ionization mass spectrometry. The derivative eluted at 10.5 min on a reverse-phase column using a mobile phase composed of 10% acetonitrile in water containing 0.5 mM sodium octyl sulfate (pH 3.0), at a column flow rate of 1.0 mL/min with UV detection at 240 nm. The optimum conditions for derivatization were a reaction temperature of 30 °C, reaction time of 30 min, and PHI concentration higher than 33.6 mM. Calibration curves were linear in the range of 0.99–19.95 μg/mL for the standard solutions and 24.9–99.7 μg/mL for the spiked sample. The proposed method was validated and proven to be selective, accurate and precise and suitable for the quantitative analysis of valiolamine in medium for microbial cultures.

Selective enrichment of albumin in biological samples by CE using segmental filling with sodium octyl sulfate in the background electrolyte

This paper shows that in CE, the peak efficiency and effective electrophoretic mobility of HSA and BSA were significantly enhanced by using a short plug (8 nL) of 1% w/w sodium octyl sulfate (SOS) and 1% w/v dextran sulfate as the additive. However, under identical conditions, other proteins did not exhibit the same phenomena. When the concentration of SOS was increased to 1.0% w/w SOS, a broad peak that corresponded to HSA transformed to a sharp peak. When the SOS concentration was more than 3.0% w/w, there was no shift in the effective electrophoretic mobility of HSA (10 microM), indicating that the binding of SOS to HSA is saturated. Through the specific interaction between SOS and HSA, the selective sweeping of HSA was accomplished using a short plug (24 nL) of 1% w/w SOS, followed by the injection of 190 nL of the sample. The excellent peak efficiency was still obtained for HSA and BSA upon the injection of a large-volume sample. As a result, the LOD for HSA (S/N=3) was 0.1 nM. In contrast to the normal injection without the SOS plug, approximately, a 4000-fold increase in the sensitivity of HSA was obtained by using the sweeping method. The proposed method has been successfully applied for the quantification of HSA in urine and erythrocytes as well as the quantification of BSA in milk.

Thermodynamic Study of Intermediate State of Papain Induced by n-Alkyl Sulfates at Two Different pH Values: A Spectroscopic Approach

The formation of the intermediate state of papain was induced by n-alkyl sulfates including sodium octyl sulfate, SOS; sodium decyl sulfate, SDeS; and sodium dodecyl sulfate, SDS at different concentrations. A systematic investigation of n-alkyl sulfates induced conformational alteration in molten globule state under an acidic condition and the native state of papain was examined by tryptophan fluorescence, 1-anilino 8-naphtalene sulfonic acid (ANS) binding and UV absorbance. The addition of n-alkyl sulfates to molten globule state at pH 2 shows a decrease in tryptophan fluorescence intensity and quenched ANS fluorescence relative to the native state that leads to enhancement in tryptophan fluorescence and an increase in ANS fluorescence as well. In the presence of n-alkyl sulfates in various conditions, two intermediate (IA and IB) with different conformations were obtained at acidic and native states, respectively. Thus, we can assume that the intermediate states in folding and unfolding pathways in various conditions have different structures. The results show that SDS is much more effective than SDeS and SOS for the formation of the intermediate states for papain in the two different pathways due to the presence of its hydrophobic tail. Therefore, hydrophobic interactions play an important role in inducing the two different intermediates along the two various thermodynamic pathways.

Compositional effects on electrophoretic and chromatographic figures of merit in electrokinetic chromatography with cetyltrimethylammonium bromide/sodium octyl sulfate vesicles as the pseudostationary phase. Part 1: Effect of the phase ratio

The effect of the phase ratio on the electrophoretic and chromatographic properties of unilamellar vesicles comprised of cetyltrimethylammonium bromide (CTAB) and sodium octyl sulfate (SOS) was investigated in EKC. The surfactant concentration of the vesicles was 0.9, 1.2, 1.5, and 1.8% w/v, with a mole ratio of 1:3.66 (CTAB/SOS). Results were compared to those obtained using SDS micelles at concentrations of 1.0% (w/v, 35 mM) and 1.5% (52 mM). The CTAB/SOS vesicles (0.9-1.8% w/v) provided a significantly larger elution range (5.7 < or = t(ves)/t(0) < or = 8.7) and greater hydrophobic (methylene) selectivity (2.8 < or = alpha(CH2) < or = 3.1) than SDS micelles (3.1 < or = t(mc)/t(0) < or = 3.3; alpha(CH2) = 2.2). Whereas the larger elution range can be attributed to the 25% reduction in EOF due to the interaction of unaggregated CTAB cations and the negatively charged capillary wall, the higher methylene selectivity is likely due to the lower concentration of water expected in the CTAB/SOS vesicle bilayer compared to the Palisades layer of SDS micelles. For a given phase ratio, CTAB/SOS vesicles are somewhat less retentive than SDS micelles, although retention factors comparable to those observed in 1.0-1.5% SDS can be obtained with 1.5-1.8% CTAB/SOS. A linear relationship was observed between phase ratio and retention factor, confirming the validity of the phase ratio model for these vesicles. Unique polar group selectivities and positional isomer shape selectivities were obtained with CTAB/SOS vesicles, with both types of selectivities being nearly independent of the phase ratio. For four sets of positional isomers, the elution order was always para < ortho < meta. Finally, the thermodynamics of solute retention was qualitatively similar to that reported for other surfactant aggregates (micelles and microemulsions); the enthalpic contribution to retention was consistently favorable for all compounds, whereas the entropic contribution was favorable only to hydrophobic solutes.

カチオン／アニオン界面活性剤混合系を利用したチタニア／界面活性剤複合粒子の調製とナノ構造制御

Titania/surfactant composite particles with nanoscale ordered structure have been prepared by hydrolysis and condensation reactions of titanium oxysulfate in the presence of molecular assemblies formed at aqueous mixtures of cationic and anionic surfactants as structure-directing agents. When cetyltrimethylammonium bromide (CTAB) and sodium octylsulfate (SOS) were used as cationic and anionic surfactants, respectively, particles with hexagonal type ordered nanostructure were obtained at CTAB-rich compositions and their repetition unit increased with increasing SOS content, while the hexagonal structure changed to lamellar structure at a certain SOS content and the repetition unit decreased above this content. These results showed that precise control of geometry and size of the nanoscale-ordered structure is possible by manipulation of the compositions of cationic CTAB and anionic SOS.

Photoinduced Increase in Vesicle Size and Role of Photoresponsive Malachite Green Leuconitrile Derivative in Vesicle Fusion

The influence of photoirradiation on vesicles containing a Malachite Green leuconitrile derivative carrying a long alkyl chain, affording photogenerated amphiphilicity, was investigated. The photoresponsive Malachite Green leuconitrile derivative was embedded in the vesicle bilayer of two single-tailed amphiphiles with oppositely charged head groups consisting of cetyltrimethylammonium chloride (CTAC) and sodium octyl sulfate (SOS). Transmission electron microscopy, which was used for observing photoinduced structural change in the vesicles, demonstrated that photoirradiation of the vesicles containing the Malachite Green leuconitrile derivative increased the average size of the vesicle diameter from 116 to 243 nm in the [CTAC]/[SOS] = 0.48 system. The mechanism for vesicle enlargement was studied with fluorescent probe molecules. The photoinduced change in the vesicle size can be explained by the destabilization of the vesicle bilayer, which is perturbed by photogenerated amphiphilicity. In addition, it was shown that the fusion process arising from the destabilized bilayer contributed to the increase in vesicle size.