Influence of Amine‐Based Cationic Gemini Surfactants on Catalytic Activity of α‐Chymotrypsin

The α‐chymotrypsin activity was tested in aqueous media with the presence of novel cationic amine–based gemini surfactant, with different spacer chain lengths and head group size, and also compared with the cationic cetyltrimethylammonium bromide (CTAB) and cetyltriphenylphosphonium bromide (CTPB) surfactants and aqueous buffer only. The p‐nitrophenyl acetate (PNPA) hydrolysis rate was monitored in the presence of the surfactant concentration at 30°C. Most of these gemini surfactants gave higher catalytic activity as compared to cationic CTAB and CTPB. The highest superactivity was measured in the presence of gemini 16‐12‐16, [dodecanediyl‐1,12‐bis(cetyldimethylammonium bromide)] surfactant at pH 7.5. The catalytic reaction follows the Michaelis–Menten mechanism. The catalytic rate constants, k_cat, show the same profile that the catalytic affinity; K_M being enhanced with increasing space chain length. The results are favorable for considering that the amine‐based gemini surfactant influences more than both the aqueous and cationic micellar media.     

Effects of head group of cationic surfactants on the hydrolysis of p‐nitrophenyl acetate catalyzed by α‐chymotrypsin

The kinetics of hydrolysis of p‐nitrophenyl acetate catalyzed by α‐chymotrypsin (α‐CT) has been studied in the presence of several cationic surfactants having different head groups maintaining the dodecyl hydrophobic residue and bromide counterion. The enzyme activity was tested in the presence of dodecyl trimethylammonium bromide (DTAB), dodecylpyridinium bromide (DPB), dodecyldimethylethanolammonium bromide (DDMEAB), dodecyldiethylethanolammonium bromide (DDEEAB), benzyldimethyldodecylammonium bromide (BDDAB), and dodecyltriphenylphosphonium bromide (DTPB) surfactants. The extent of superactivity depends upon head groups of surfactants. The activity of α‐CT depends on the surfactant concentration and it varies with the surfactant head group dimensions (DTPB > DDEEAB > DTAB > BDDAB > DDMEAB > DPB). For all surfactants, DTPB exhibits highest superactivity. The effects of surfactants on the apparent kinetic parameters like Michaelis constant K_m and the catalytic constant k_cat have been determined. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 377–381, 2009     

Activity of α‐Chymotrypsin in Cationic and Nonionic Micellar Media: Ultraviolet and Fluorescence Spectroscopic Approach

α‐Chymotrypsin (α‐CT) activity was measured in aqueous buffer with the following alkyltriphenylphosphonium bromide surfactants in the series cetyl, tetradecyl, and dodecyl as a tail length. For the sake of comparison with mixed micellar investigation on activity of α‐CT, cationic cetyltriphenylphosphonium bromide (CTPB) and nonionic surfactant Triton X‐100, Brij‐56, Brij‐35, Tween 20, and Igepal Co‐210 have been used. The p‐nitrophenyl acetate (PNPA) hydrolysis rate was determined at the surfactant concentration of both cationic and mixed micellar systems by a UV–vis spectrophotometer. The catalytic reaction follows the Michaelis–Menten mechanism, and the catalytic efficiency (k_cat/K_M) was evaluated for both homogeneous and mixed‐micellar media. The maximum catalytic efficiency was observed at 5 mM concentration of CTPB, but the highest catalytic efficiency, 572 M^?1 s^?1, was measured in the presence of mixed micellar (7.5 mM CTPB + 2.5 mM Tween‐20). The fluorescence (FL) spectra showed the differences of α‐CT conformations in the presence of cationic surfactants. The FL results suggest that the influence of cationic surfactant on proteolysis arises from the interaction with the α‐CT. The binding constant, k_sv, of α‐CT with cationic aggregates was determined in the buffer using the Stern–Volmer equation by the fluorescence spectroscopic approach.     

卵清蛋白与离子型表面活性剂的相互作用

本文通过荧光光谱法、紫外-可见吸收光谱法和透射电镜并结合电导率测定分别研究了水中卵清蛋白与阴离子表面活性剂十二烷基硫酸钠（SDS）和阳离子表面活性剂十二烷基三甲基溴化铵（DTAB）和十六烷基三甲基溴化铵（CTAB）之间的相互作用。研究结果表明卵清蛋白可以增加SDS和CTAB的临界胶束浓度,但对DTAB的临界胶束浓度没有影响。阴离子表面活性剂可以使卵清蛋白构象完全伸展,而阳离子表面活性剂却不具备此种作用。表面活性剂单体与卵清蛋白的相互作用强于表面活性剂胶束与卵清蛋白的相互作用。     

Oil Solubilization Capacity,Liquid Crystalline Properties,and Antibacterial Activity of Alkanolamine‐Based Novel Cationic Surfactants

A series of monomeric and dimeric cationic surfactants with tuned polarity was synthesized. Oil solubilization capacity, thermotropic liquid crystalline properties, and minimum inhibitory concentration (MIC) of novel hydroxylated cationic surfactants using selected gram positive and gram negative bacteria were examined. Antibacterial activity and the propensity of gemini surfactants for oil solubilization were observed to be better than those of corresponding monomeric surfactants. Pseudo ternary phase diagrams for these surfactants, methyl methacrylate (MMA), and water clearly showed, that microemulsions can be easily formulated with all these surfactants. Solubilization and foam studies of mixed surfactant systems were also examined. Molecular architecture like the tail length, head group area, and presence of ethanolic goups in the surfactant affect the performance properties. Unlike conventional gemini surfactants the synthesized gemini surfactants also show thermotropic liquid crystalline properties (smectic‐A, L_α phase).     

Optical Sensing Membrane Based on Tetrabromophenolphthalein Ethyl Ester for the Determination of Cationic Surfactants

Abstract

An optical sensing membrane for detection of cationic surfactants was developed. The optical sensing membrane is 2‐nitrophenyl octyl ether‐plasticized poly(vinyl chloride) membrane incorporating tetrabromophenolphthalein ethyl ester (TBPE). The response of the optical membrane to cationic surfactants was a result of extraction of cationic surfactant into the PVC membrane. The protonated TBPE deprotonates forming an ion associate with the extracted cationic surfactant; simultaneously, the deprotonation of the TBPE is accompanied by a spectral change. Namely, the extracted cationic surfactant changes color of the membrane from yellowish green to blue (absorption maximum: 622 nm). The optical membrane responds to cationic surfactants such as Zephiramine and cetyltrimethylammonium bromide in the concentration range from 1 µM to 100 µM.     

Interactions between nonpolar surfaces in mixed solutions of cationic and nonionic surfactants

The interaction energy between hydrophobic SiO₂ particles in aqueous solutions of a cationic surfactant (dodecylpyridinium bromide, DDPB), a nonionic surfactant (Triton X-100, TX-100), and their mixed solutions was measured as a function of concentration. Synergism has been observed in mixed surfactant solutions: the surfactant concentration required for achieving the set interaction energy in the mixed solutions was lower than in the solutions of the individual surfactants. The molecular interaction parameters in surfactant mixtures were calculated using the Rosen model. Chain-chain interactions between nonionic and cationic surfactants were suggested as the main reason for the synergism.     

Mixing Behavior of Conventional and Gemini Cationic Surfactants

Micellization behavior of cationic monomeric surfactants, hexadecyltrimethylammonium bromide (CTAB), cetylpyridinium bromide (CPB), cetylpyridinium chloride (CPC), tetradecyltrimethylammonium bromide (TTAB), and dimeric (gemini) cationic surfactant pentamethylene‐1, 5‐bis(hexadecyldimethylammonium bromide) with formula C₁₆H₃₃(CH₃)₂N⁺(CH₂)₅N⁺(CH₃)₂C₁₆H₃₃ · 2Br^?, abbreviated as 16‐5‐16, in mixed states (binary) have been studied by conductivity. The micellar compositions, activities of the components, and their mutual interactions have been estimated from Rubingh's theory. The mixtures show nonideal behavior with favorable interactions.     

Binary Coalescence of Water Drops in Organic Media in Presence of Ionic Surfactants and Salts

Binary coalescence of water drops in o‐xylene and toluene, and ethylene glycol drops in toluene were studied in this work. The effects of cationic and anionic surfactants on coalescence time were studied. Cetyl trimethyl ammonium bromide (CTAB) and cetyl pyridinium bromide (CPyBr) were used as cationic surfactants. Sodium dodecyl benzene sulfonate (SDBS) was used as the anionic surfactant. The effects of salts (NaCl and CaCl₂) containing monovalent and divalent ions on coalescence were investigated. The coalescence time was found to follow distributions in each of these experiments. The minimum and maximum values of the distributions were largely different. The stochastic model developed earlier by us was used to fit the distributions. The effects of the physical properties of the system (such as density, size of the drops, interfacial tension, and surface excess of adsorbed surfactant) on the model parameters were discussed.     

Mixed Micellization Behavior of 12-2-12 Gemini Surfactant with Some Alkyltrimetyl Ammonium Bromide Surfactants

Mixed micellization behavior of dimeric cationic surfactant ethanediyl-1,2-bis (dimethyldodecylammonium bromide) (12-2-12) with a series of monomeric cationic surfactants dodecyltrimethyl ammonium bromide (DTAB), tetradecyltrimethyl ammonium bromide (TTAB), and cetyltrimethyl ammonium bromide (CTAB) has been studied in aqueous and aqueous polyvinylpyrrolidone (PVP) solutions at 298.15, 308.15, and 318.15 K, respectively, using conductometric method. Various thermodynamic parameters like mixed micelle concentration (C_m), micelle mole fraction (X₁), interaction parameter (β), and free energy of mixing (ΔG_ex) of the mixed systems have been determined and analyzed using Rubingh's regular solution theory. The results indicate that in aqueous solutions the binary mixtures of 12-2-12 with DTAB/TTAB behave nonideally with mutual synergism whereas that with CTAB shows almost ideal behavior at 298.15 K. At 318.15 K, all these binary mixtures exhibit antagonistic behavior. The effect of variation in chain length of alkyltrimethyl ammonium bromide surfactants on the interactions with 12-2-12 have also been evaluated and discussed.     

Cationic Surfactants as Regulators in Paper Separation of 2‐Nitrophenol and 2,4,6‐Trinitrophenol in Water

The chemical pollutants 2‐nitrophenol (2‐NP) and 2,4,6‐trinitrophenol (2,4,6‐TNP) were studied for their separation from water by the paper capillary permeation adsorption technique by the use of the four cationic surfactants dodecyltrimethylammonium chloride (DTAC), tetradecyltrimethylammonium bromide (TTAB), cetyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC) as regulators. The effect of pH and the concentration of surfactant on the separatability have been investigated. A nearly 100% separatability was obtained for each pollutant at its optimum pH and surfactant concentration. It was shown that the separation was accomplished via surface adsorption onto the fibers of paper. The change in separatability at basic pH 11 with surfactant variety was analyzed. The result shows that the surfactant with a longer chain alkyl group is more effective for the separation of 2‐NP and the surfactants with 16 carbons in the long chain alkyl group are most effective. The surfactants with 12 carbons or more in the long alkyl group but containing no aromatic group such as pyridyl group are equally effective for accomplishing an efficient separation of 2,4,6‐TNP. Selective separation of 2‐NP from an admixture of 2‐NP plus 2,4,6‐TNP was attempted. The optimum surfactant for each pollutant was tested with seawater for removing the pollutant. The goal of this study is to search for an optimum cationic surfactant and optimum separation conditions for nitrophenols.     

Vesicle formation between single-chained cationic surfactant and plasmid DNA and its application in cell transfection

In the present study, we found that plasmid DNA could induce single-chained cationic surfactants cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), and dodecyltriethyl ammonium bromide (DEAB) to form vesicles once its concentration reached a critical value. Moreover, the gene for follicle-stimulating hormone was delivered into cells with these single-chained cationic surfactant/DNA vesicles and the transfection efficiency was comparable to that with lipofectamine? 2000, a famous and widely used commercial transfection reagent, and also to that using electroporation method, although it was generally thought conventional single-chained cationic surfactant was not suitable for gene transfer. The conventional single-chained cationic surfactant is very cheap and stable and the vesicles are very easy to be prepared. Thereby, this study may suggest that the vesicles formed between plasmid DNA and surfactant should be prospective to transfer DNA.     

Which are the mechanisms governing in cationic emulsion polymerization?

The cationic emulsion polymerization of styrene in a batch reactor using different concentrations of dodecyltrimethylammonium bromide (DTAB) and hexadecyltrimethyl-ammonium bromide (HDTAB) as cationic surfactants, and 2,2′-azobisisobutyramidine dihydrochloride (AIBA), and 2,2′-azobis (N,N′-dimethyleneisobutyramidine) dihydrochloride (ADIBA) as cationic initiators has been studied. In the preliminary study, the best conditions to obtain stable cationic latexes at high conversions were identified. When the surfactant concentration was above its cmc, latexes with high conversions were achieved for the two cationic surfactants studied (DTAB and HDTAB). Cationic latexes with less coagulum were obtained using ADIBA as cationic initiator due to its superior resistance to hydrolysis. AIBA is hydrolyzed to amide at basic pHs and in this way, the concentration of radicals formed in the aqueous phase decreases. On the other hand, a stronger effect of the particle size on the kinetics of the cationic emulsion polymerization of styrene using HDTAB as cationic surfactant was observed than using DTAB. Furthermore, different kinetic behaviors were observed with the two cationic initiators (ADIBA and AIBA) using HDTAB as cationic surfactant, due to the lower stabilizing effect of the cationic radicals provided by AIBA.     

Micellar‐accelerated hydrolysis of organophosphate and thiophosphates by pyridine oximate

Rate constants for the hydrolysis reaction of phosphate (paraoxon) and thiophosphate (parathion, fenitrothion) esters by oximate (pyridinealdoxime 2‐PyOx⁻ and 4‐PyOx⁻) and its functionalized pyridinium surfactants 4‐(hydroxyimino) methyl)‐1‐alkylpyridinium bromide ions (alkyl = C_nH_2n+1, n = 10, 12, 14, 16) have been measured kinetically at pH 9.5 and 27°C in micellar media of cationic surfactants cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB). Acid dissociation constant, pK_a, of oximes has also been determined by spectrophotometric, kinetic, and potentiometric methods. The rate acceleration effects of cationic micelles have been explored. Cationic micelles of the pyridinium head group (CPB) showed a large catalytic effect than the ammonium head group (CTAB). The effects of pH, oximate concentration, and surfactants have been discussed.     

Rheological properties of the aqueous solution for fluorocarbon‐containing hydrophobically modified sodium polyacrylic acid with various surfactants

The interaction of fluorocarbon‐ containing hydrophobically modified sodium polyacrylic acid (FMPAANa) (0.5 wt%) with various surfactants (anionic, nonionic and cationic) has been investigated by rheological measurements. Different rheological behaviors are displayed for ionic surfactants and nonionic surfactants. Fluorinated surfactants have stronger affinity with polyelectrolyte hydrophobes comparing with hydrogenated surfactants. The hydrophobic association of FMPAANa with a cationic surfactant (CTAB) and a fluorinated nonionic surfactant (FC171) is much stronger than with a nonionic surfactant (NP7. 5) and an anionic surfactant (FC143). Further investigation of the effects of temperature on solution properties shows that the dissociation energy E_m is correlated to the strength of the aggregated junctions.     

Interaction between two homologues of cationic surface active ionic liquids and the PEO-PPO-PEO triblock copolymers in aqueous solutions

The interaction of nonionic triblock copolymers of poly(ethyleneoxide) (PEO) and poly(propyleneoxide) (PPO) (PEO_nPPO_mPEO_n) with a series of cationic surface-active ionic liquids in aqueous solutions have been investigated. The cationic surface-active ionic liquids include 1-alkyl-3-methylimidazolium bromide (C_nmimBr, n?=?8, 10, 12, 14, 16) and N-alkyl-N-methylpyrrolidinium bromide (C_nMPB, n?=?12, 14, 16). For different polymer-surfactant systems, the critical aggregation surfactant concentration (cac), the surfactant concentration to form free micelles (C _m), and the saturation concentration of surfactant on the polymer chains (C ₂) were determined using isothermal titration microcalorimetry (ITC) and conductivity measurements. The structure of the formed aggregates depended strongly on the hydrophobicity of the surfactant and the ratio of polymer/surfactant concentration. For C₈mimBr, there were not any micelle-like surfactant?Cpolymer clusters detected in the solution, and only micelles appeared. For other surfactants, the polymer?Csurfactant aggregates were formed in the solution, which was verified by the appearance of a broad endothermic peak in the ITC thermograms. The intensity of polymer?Csurfactant interaction increased with the hydrophobicity of the surfactants and the polymers but was not affected by the surfactant headgroups.     

Micelle Formation and Aggregate Morphology Transition from Vesicle to Rod Micelle for Allyl Alkyldimethylammonium Bromide Cationic Surfactant

A series of cationic surfactants of allyl alkyldimethylammonium bromide (AA_nDB), where n=12, 16, 18, were synthesized, and the adsorption behavior of AA_nDB at the air–water interface and the aggregation morphology in bulk solution were reported. The critical micelle concentration (CMC) was determined by the drop volume technique and steady state fluorescence. The surface excess concentration of AA_nDB surfactants was calculated from the surface tension versus log concentration curves by applying the Gibbs' adsorption isotherm. The values of surface area per molecule calculated by using Gibbs' equation were 2.9–1.4 nm², indicating the relatively large size of the AA_nDB surfactants. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements reveal that, at low surfactant concentration of allyl dodecyl dimethylammonium bromide (AA₁₂DB) above CMC, vesicles can be spontaneously formed. However, with increasing surfactant concentration, vesicles tend to be transformed into rod‐like micelles.     

Enhanced separation of Compound Xueshuantong capsule using functionalized carbon nanotubes with cationic surfactant solutions in MEEKC

A novel additive of multi‐walled carbon nanotubes (MWNTs) dispersed with cationic surfactants or mixed cationic/anionic surfactants was used for MEEKC separation of eight phenolic compounds, four glycosides, and one phenanthraquinone. In this context, several parameters affecting MEEKC separation were studied, including the dispersion agents of MWNTs, MWNTs content, oil type, SDS concentration, and the type and concentration of cosurfactant. Compared with conventional MEEKC, the addition of all types of MWNTs dispersions using single or mixed cationic surfactant solutions in running buffers was especially useful for improving the separation of solutes tested, as they influenced the partitioning between the oil droplets and aqueous phase due to the exceptional electrical properties and large surface areas of MWNTs. Use of cationic surfactant‐coated MWNTs (6.4 μg/mL) as the additive in a microemulsion buffer (0.5% octanol, 2.8% SDS, 5.8% isopropanol, and 5 mM borate buffer) yielded complete resolution of 13 analytes. The proposed method has been successfully applied for the detection and quantification of the studied compounds in a complex matrix sample (Compound Xueshuantong capsule).     

Interaction Parameters of Anhydrous Cationic Surfactant Mixtures by Inverse Gas Chromatography

The miscibility of anhydrous cationic surfactant dodecylpyridinium chloride (DPC) and hexadecylpyridinium bromide (cetylpyridinium bromide (CPB)) mixtures has been studied by using them as stationary phases in Inverse Gas Chromatography (IGC). The temperature zone of work was determined by IGC and Differential Scanning Calorimetry (DSC) techniques. Values of the interaction parameter between the surfactants obtained at four different compositions and at four temperatures showed that the miscibility depends on the overall composition and suggested that the interactions are more favorable near the center of the composition range. Results are compared with other anhydrous cationic surfactant mixtures studied by IGC, the system didodecyldimethylammonium bromide (DDAB) and dioctadecyldimethylammonium bromide (DODAB), two twin-tailed surfactants, and are interpreted in terms of the structure of the anhydrous lamellar liquid crystals compared with that of aqueous lamellar mesophases.     

Employment of a useful liquid membrane electrode system to characterise the micelles of bile salts and other detergents in pure and mixed states

Ion-pairs or coacervates (formed by the reaction between cationic and anionic surfactants) dissolved in nitrobenzene can behave as surfactant-ion registering devices to respond to both surfactant cation and anion. The complexes of cetyltrimethyl ammonium bromide with sodium dodecyl sulfate, sodium salts of deoxycholic and chenodeoxycholic acids, and Aerosol Orange T have been used in nitrobenzene to generate such useful liquid membranes. The complex of dimethyldioctadecyl ammonium bromide and sodium cholate has been used to study the cholate ion behaviour since its complex with cetyltrimethyl ammonium bromide is water soluble. The electrochemical behaviours of the liquid membranes have been found to be fairly good and reproducible. The membrane potential measurements have been used to determine the critical micelle concentrations of the surfactants in pure as well as in mixed states to evaluate surfactant—surfactant interaction in the micelles of the latter.