Growth rate and some physiological features of Deleya halophila CCM 3662 at different salt concentrations

The growth rate of the type strain of the new, moderately halophilic species Deleya halophila (Deleya halophila CCM 3662) at different salt concentrations was determined and its optimal marine salt concentration for growth was established. Oxygen uptake and some cellular chemical composition characteristics of cells grown at their optimal salt concentration (7.5 % w/v) and at a higher concentration (15 % w/v) were compared, showing that both protein and carbohydrate intracellular contents decreased when the external medium salt concentration was increased, with the carbohydrate content reaching 50 % of the value presented by cells cultured at optimal salinity conditions. Oxygen uptake and poly-β-hydroxybutyric acid content were not significantly affected by changes in external salinity.     

2-DE using hemi-fluorinated surfactants

The synthesis of hemi-fluorinated zwitterionic surfactants was realized and assessed for 2-DE, a powerful separation method for proteomic analysis. These new fluorinated amidosulfobetaine (FASB-p,m) were compared to their hydrocarbon counterparts amidosulfobetaine (ASB-n) characterized by a hydrophilic polar head, a hydrophobic and lipophilic tail, and an amido group as connector. The tail of these FASB surfactants was in part fluorinated resulting in the modulation of its lipophilicity (or oleophobicity). Their effect on the red blood cell (RBC) membrane showed a specific solubilization depending on the length of the hydrophobic part. A large number of polypeptide spots appeared in the 2-DE patterns by using FASB-p,m. The oleophobic character of these surfactants was confirmed by the fact that Band 3, a highly hydrophobic transmembrane protein, was not solubilized by these fluorinated structures. The corresponding pellet was very rich in Band 3 and could then be solubilized by using a strong detergent such as amidosulfobetaine with an alkyl tail containing 14 carbon atoms (ASB-14). Thus, these hemi-fluorinated surfactants appeared as powerful tools when used at the first step of a two-step solubilization strategy using a hydrocarbon homologous surfactant in the second step.     

Growth, Osmolyte Concentration and Antioxidant Enzymes in the Leaves of Sesuvium portulacastrum L. Under Salinity Stress

In this study, growth and osmolyte concentration in the leaves of halophyte, Sesuvium portulacastrum, were studied with respect to salinity. Therefore, the changes in shoot growth, leaf tissue water content, osmolyte concentration (proline content, glycine betaine) and antioxidant enzymes [polyphenol oxidase (PPO), superoxide dismutase (SOD) and catalase (CAT)] were investigated. The 30-day old S. portulacastrum plants were subjected to 100, 200, 300, 400, 500 and 600 mM NaCl for 28 days. The plant growth was steadily increased up to 500 mM NaCl stress at 28 days. TWC was higher in 300 mM NaCl treated leaves than that of 600 mM NaCl. Salinity stress induced the accumulation of osmolyte concentration when compared to control during the study period. The antioxidant enzymes PPO, CAT and SOD were increased under salinity.     

Determination of alkylphenol ethoxylates by micellar electrokinetic chromatography with bile salts

Octyl- and nonylphenol ethoxylates (OPEs and NPEs) with different numbers of ethoxy units (average values: n = 10 and N = 40 for OPEs, and n = 10 for NPEs) were separated by micellar electrokinetic chromatography under positive polarity using an 80 mM borate buffer of pH 8.5 containing sodium deoxycholate (SDC) or sodium cholate (SC). When sodium dodecyl sulfate (SDS) was added to the background electrolyte (BGE) in the absence of the bile salt, a single peak at a migration time longer than that of the EOF was obtained. Substituting the SDS by a bile salt, the homologues were resolved. At the same bile salt concentration, resolution between the homologues was higher with SDC than using SC. Optimum resolution between consecutive homologues was obtained with 50 mM SDC. In the presence of low or moderate amounts of acetonitrile or n-propanol, the background line improved significantly, whereas resolution may increase or decrease slightly. We propose a procedure for the determination of OPEs and NPEs with optimum resolution between the homologues as well as a modified procedure with improved selectivity for the single-run determination of other absorbing nonionic, cationic, and anionic (such as linear alkylbenzene sulfonates) surfactants in industrial and household cleaning products and its application to a variety of samples. The detection limit was ca. 28 microg x mL(-1) of total NPE (n = 10), and peak area repeatabilities at 50 microg x mL(-1) were 1.7% (intraday) and 5.6% (interday).     

Simultaneous determination of cationic surfactants and nonionic surfactants by ion-association titration.

A simultaneous determination of cationic and nonionic surfactants has been developed using ion-association titration. Tetrabromophenolphthalein ethyl ester (TBPE) was used as an indicator. Benzalkonium reacted with TBPE to form a blue ion-associate in the organic phase. When tetrakis(4-fluorophenyl)borate was added dropwise to the solution, the color of the organic phase turned to yellow at the equivalence point. In addition, when a large amount of potassium ion was added to a solution including Triton X-100, Triton X-100 could be determined by the same technique as described above because of formation of the K+-Triton X-100 cation. The proposed method is available for the stepwise determination of cationic and nonionic surfactants in mixtures.     

From Gold Nanoseeds to Nanorods: The Microscopic Origin of the Anisotropic Growth

Directly manipulating and controlling the size and shape of metal nanoparticles is a key step for their tailored applications. In this work, molecular dynamics simulations were applied to understand the microscopic origin of the asymmetric growth mechanism in gold nanorods. Different factors influencing the growth were selectively included in the models to unravel the role of the surfactants and ions. In the early stage of the growth, when the seed is only a few nanometers large, a dramatic symmetry breaking occurs as the surfactant layer preferentially covers the (100) and (110) facets, leaving the (111) facets unprotected. This anisotropic surfactant layer in turn promotes anisotropic growth with the less protected tips growing faster. When silver salt is added to the growth solution, the asymmetry of the facets is preserved, but the Br^? concentration at the interface increases, resulting in increased surface passivation.     

New thermodynamic/electrostatic models of adsorption and tension equilibria of aqueous ionic surfactant mixtures: application to sodium dodecyl sulfate/sodium dodecyl sulfonate systems

The nonideal adsorbed solution (NAS) theory has been formally extended to adsorption at the air/water interface from aqueous mixtures of ionic surfactants, explicitly accounting for the surface potential of the adsorbed monolayer with the Gouy-Chapman theory. This new ionic NAS (iNAS) theory is thermodynamically consistent and, when coupled to a micellization model, is valid for concentrations below and above the mixed cmc. Counterion binding is incorporated into the model using two fractional binding parameters, beta(sigma) for the adsorbed monolayer and beta(m) for the micelles. The regular solution theory is used to model the nonideal interactions within the adsorbed monolayer and within the mixed micelles. New tension data for an equimolar mixture of sodium dodecyl sulfate (SDS) and sodium dodecyl sulfonate (SDSn) at two salinities fit this model well when mixing is ideal. The total surface densities, the surface compositions, and the surface potentials for the mixed monolayers are calculated. When there is no added salt, at total surfactant concentrations below the mixed cmc, the adsorbed monolayer is enriched in SDSn, but at total concentrations at and above the mixed cmc, the adsorbed monolayer is nearly an equimolar mixture. In the presence of 100 mM NaCl, the adsorbed monolayer is nearly an equimolar mixture, independent of the total surfactant concentration.     

A novel ion chromatographic method based on cation-exchange and acid-base interactions for the simultaneous determination of total alkalinity and monovalent cations in samples of microliter volume

An ion chromatographic (IC) method based on the use of titrant (strong acid) as the stationary phase was developed for simultaneous determination of total alkalinity (TA) and monovalent cations. The titrant used in this study was obtained by initially loading lithium dodecylsulfate (Li-DS) onto a reversed-phase material and then conditioning the column with a slightly acidified aqueous LiCl solution (a mixture of 50.0 mM LiCl and 0.1 mM H2SO4). When a small amount of a basic sample was injected onto a column prepared in this way, the basic species (Bn-) reacted predominantly with H+ on the stationary phase and the reaction with the eluent phase was negligible due to the very low concentration of eluent H+ (in the eluent, a molar ratio of [Li+]/[H+] = 250:1 applied). The stationary phase H+ consumed in the acid-base reaction was then re-supplied by H+ from the eluent. By monitoring the conductance of the eluent using conductivity, an induced peak resulting from the basic species was observed. Calibration graphs of peak areas vs. molar concentration of the basic species for OH-, HCO3- and H2PO4- were found to be identical. CO3(2-), HPO4(2-), and B4O7(2-) also gave identical calibration curves but their slope values were twice those for HCO3-. The detection limit for HCO3- was less than 3.2 microM and the calibration curve was linear up to 12.3 mM (injection volume, 100 microL). Seawater was directly analyzed and its total alkalinity was found to be 2.87 mM (RSD 0.53%, n = 5), which was in good agreement with the result of 2.88 mM (RSD 3.2%, n = 5) obtained using auto-potentiometric titration. Na+ and K+ were determined simultaneously and the concentrations were 481.6 and 10.6 mM, respectively.     

Degradation of alkylbenzene sulfonate surfactants by pulsed ultrasound

The application of pulsed ultrasound for the degradation of the nonvolatile surfactants sodium 4-octylbenzene sulfonate (OBS) and sodium dodecylbenzenesulfonate (DBS) was investigated at a frequency of 354 kHz. By comparing the degradation rate constants with those of continuous wave (CW) ultrasound, observed pulse enhancements were found to be dependent on the pulse length, pulse ratio, initial concentration, and surface activity of the surfactants. For a pulse length of 100 ms and a pulse ratio of 1:1 (equal on/off times), the degradation rate constant of 1 mM OBS was nearly twice the value for CW. Furthermore, the degradation rate constant for 1 mM DBS increased significantly when sonicated under a pulse length of 100 ms and a pulse on/off ratio of 1:50. However, the degradation rate of 0.1 mM OBS increased by only 30% with a 100 ms pulse length and pulse ratio of 1:1 as compared to CW, indicating concentration dependence. The enhanced degradation of surfactants by pulsed ultrasound was attributed to the accumulation of surfactants on cavitation bubble surfaces. In addition, as compared to shorter pulse intervals, longer pulse intervals enhanced DBS degradation, indicating that DBS, a more surface active compound, accumulated and equilibrated with the bubble interface more slowly.     

The modification of the triple helical structure of gelatin in aqueous solution 3. The influence of cationic surfactants

The interaction between cationic surfactants (hexadecyl and dodecyl trimethyl ammonium bromide) and gelatin was characterized by measuring the circular dichroism. The interaction between the cationic surfactants and gelatin is weak in comparison to that of anionic surfactants. When the concentration of cationic surfactants is sufficiently low, refolding of the gelatin-strands to the triple helical structure by rechilling the solution from 298 K to 283 K is complete. The triple helical content of the solution is affected more strongly by the cationic surfactants in acidic solution than at pHs 7 or 10. The interaction depends on the apolar group of the surfactant and is found to be stronger for DTAB than for CTAB at 298 K. Coagulation of the hydrophobic gelatin-cationic surfactant complexes does not comprise that pan of gelatin which is able to refold the triple helical structure. Therefore, the gelatin-strands of lower molecular weights are thought to react favorably with the surfactant ions.     

Polymethylmethacrylate derivatives Eudragit E100 and L100: Interactions and complexation with surfactants

Precipitation or coprecipitation of polyelectrolytes has been largely investigated. However, the precipitation of polyelectrolytes via addition of charged and non‐charged surfactants has not been systematically studied and reported. Consequently, the aim of this work is to investigate the effect of different surfactants (anionic, cationic, non‐charged and zwitterionic) on the precipitation of cationic and anionic polymethylmethacrylate polymers (Eudragit). The surfactants effect has been investigated as a function of their concentration. Special attention has been dedicated to the CMC range and to the colloidal characterization of the formed dispersions. Moreover, the effect of salt (NaCl) and pH was also addressed. It is pointed out that non‐ionic and zwitterionic surfactants do not interact with charged Eudragit E100 and L100. For oppositely charged Eudragit E100/SDS and Eudragit L100/CTAB, precipitation occurs, and the obtained dispersions have been characterized in terms of particle size distribution and zeta potential. It was established that the binding of SDS molecules to Eudragit E100 polymer chains is made through the negative charges of the surfactant heads under the CMC value whereas binding of CTAB to Eudragit L100 chains is made at a CTAB concentration 5 times above its CMC. For Eudragit E100/SDS system, a more acidic medium induces aggregation. A same result was observed for the Eudragit L100/CTAB at a more basic pH. Moreover, it was observed that increasing salt concentration (higher than 100 mM) led to aggregation as generally observed for polycations/anionic surfactant systems.     

Salinity stress enhances production of solasodine in Solanum nigrum L

Various in vitro grown tissues (non-regenerative callus, regenerative callus and microshoot derived leaves) of Solanum nigrum L. were cultured under salinity stress (0-150 mM NaCl) for enhanced production of solasodine, a steroidal alkaloid and an alternative to diosgenin, which is used as a precursor for the commercial production of steroidal drugs. The role of plant growth regulators and various concentrations of NaCl during in vitro production of solasodine was studied. The in vitro yield was compared with the yield from leaves of field grown plant. Solasodine content was maximum (2.39 mg/g dry wt.) in regenerative callus when grown on medium added with 150 mM NaCl; followed by in vitro raised leaf of microshoot. Quantitative estimation of solasodine was carried out using a new HPTLC method, which is validated for its recovery and precession. The proposed HPTLC method showed a good linear relationship (r(2)=0.994) in 50-2000 ng/spot concentration ranges. The data demonstrate that the solasodine production in cultures was growth dependent.     

Effect of Encapsulated Beet Extracts (Beta vulgaris) Added to Yogurt on the Physicochemical Characteristics and Antioxidant Activity

Beet has been used as an ingredient for functional foods due to its high antioxidant activity, thanks to the betalains it contains. The effects of the addition of beet extract (liquid and lyophilized) on the physicochemical characteristics, color, antioxidant activity (AA), total betalains (TB), total polyphenols (TP), and total protein concentration (TPC) were evaluated on stirred yogurt. The treatments (T1-yogurt natural, T2-yogurt added with beet juice, T3-added extract of beet encapsulated with maltodextrin, and T4-yogurt added with extract of beet encapsulated with inulin) exhibited results with significant differences (p < 0.05). The highest TB content was observed in T2 (209.49 ± 14.91), followed by T3 (18.65 ± 1.01) and later T4 (12.96 ± 0.55). The highest AA was observed on T2 after 14 days (ABTS˙ 0.819 mM TE/100 g and DPPH˙ 0.343 mM TE/100 g), and the lowest was found on T1 at day 14 (ABTS˙ 0.526 mM TE/100 g and DPPH˙ 0.094 mM TE/100 g). A high content of TP was observed (7.13 to 9.79 mg GAE/g). The TPC varied between 11.38 to 12.56 µg/mL. The addition of beet extract significantly increased AA in yogurt, betalains being the main compounds responsible for that bioactivity.     

Preparation and solution properties of a novel cationic hydrophobically modified polyacrylamide for enhanced oil recovery

Abstract

A novel cationic water-soluble monomer allyldimethylisooctylammonium bromide (ADIAB) containing a short-chain alkane was synthesized successfully. This monomer was copolymerized with acrylamide and sodium acrylate to produce hydrophobically modified polyacrylamide (HMPAM) using solution polymerization without surfactants. The structures of monomer ADIAB and HMPAM were characterized with infrared spectroscopy and nuclear magnetic resonance spectroscopy. Influence of preparation condition on viscosities of products was studied. The aqueous solution viscosity of the terpolymer was also investigated as functions of concentration, temperature and salinity. The results showed that when the temperature exceeds the 60?°C and NaCl concentration exceeds about 2000?mg/L, the temperature and salt tolerance characters of terpolymer were demonstrated. The enhanced oil recovery tests were initially carried out using homogeneous sandpack models.     

The Stability of the Micelle Formed by Chain Branch Surfactants and Polymer Under Salt and Shear Force: Insight from Dissipative Particle Dynamics Simulation

The influence of salt and shear force on the stability of the micelle formed by surfactants and polymer are studied using dissipative particle dynamics (DPD) simulation method. The research system mainly includes four types of surfactants with different hydrophilic/hydrophobic chain branches and two kinds of polymers with hydrophilic/hydrophobic properties, respectively. The stability of the micelle is studied based on the analyses of the density peak and root mean square (RMS) of polymer chain under different salt and shear force. The calculated results show that the density peak reduced and RMS increased for all surfactants with the salt concentration and shear force increasing, and then indicate that the micelle has a certain degree of deformation. Whereas, the surfactant chain branch has important influence on the deformation extent of the micelle. For hydrophobic polymer, surfactants containing hydrophobic chain branch (T2H2T2) are beneficial to the stability of the micelle. On the contrary, for hydrophilic polymer, the micelle formed by surfactants with stronger hydrophilic nature such as the hydrophilic groups located in the both ends of the molecule (H1T4H1) have the best salt and shear resistance. The results have certain theoretical significance and can provide theoretical support for the selection of surfactants and polymers in practical application.     

Microcalorimetric study on the interaction of dissymmetric gemini surfactants with DNA

The interaction of a series of dissymmetric gemini surfactants, [C(m)H(2m+1)(CH(3))(2)N(CH(2))(6)N(CH(3))(2)C(n)H(2n+1)]Br(2) (designated as C(m)C(6)C(n)Br(2), with constant m+n=24, and m=12, 14, 16, and 18) with DNA in 10 mM NaCl solution has been investigated by isothermal titration microcalorimetry (ITC). The curves for titration of the surfactants into DNA solution show noticeable differences from those into 10 mM NaCl solution without DNA. It is attributed to the interaction between DNA and surfactants. The critical aggregation concentration (CAC), the saturation concentration (C(2)), and the thermodynamic parameters for the aggregation and interaction processes were obtained from the calorimetric titration curves. The results show that the dissymmetry degree (m/n) has a marked effect on the interaction of the C(m)C(6)C(n)Br(2) surfactants with DNA. The CAC and C(2) tend to become smaller with increased m/n. The enthalpy change (DeltaH(agg)) and the Gibbs free energy change (DeltaG(agg)) for aggregation become more negative down the series, indicating that the hydrophobic interaction between the hydrophobic chains of the surfactant molecules increases and the aggregation process is more spontaneous with increased m/n. The entropy changes of aggregation (DeltaS(agg)) are all positive and TDeltaS(agg) is much larger than |DeltaH(agg)|, revealing that the aggregation process is mainly entropy-driven. However, the calculated Gibbs free energy (DeltaG(DS)) for the interaction between the gemini surfactants and DNA becomes less negative with increased m/n, which reveals that the interaction between the gemini surfactants and DNA tends to be weaker with increased m/n. This is induced by the disruption of the chain-chain hydrophobic interaction between the surfactant molecules at higher m/n, where the entropy change DeltaS(DS) for the interaction process tends to be an unfavorable factor. In addition, the DNA concentration also has a remarkable influence on the interaction.     

Effect of Surfactants and Carbon Nanomaterials on the Electroflotation Extraction of the Disperse Phase of Cobalt Hydroxides

The effect of surfactants and carbon nanomaterials (CNMs) on the electroflotation extraction of the disperse phase of cobalt(II) and (III) hydroxides at pH 6 and pH 10 was studied. It is shown that at pH 6 in the absence of surfactants, the efficiency of cobalt extraction in various electrolytes is low and does not exceed 15–25%. In the surfactant–CNM–electrolyte system, the degree of extraction α increases in the chloride, nitrate, and sulfate solutions compared with the solutions containing no surfactants. The electroflotation extraction of cobalt was more efficient at pH 10: α reached 80–96% in the absence of surfactants, 70–97% in the surfactant–electrolyte system, and 60–97% in the surfactant–CNM–electrolyte system. The optimum conditions of the electroflotation extraction of cobalt hydroxides from solutions containing various inorganic electrolytes were determined. The effect of the sodium chloride content on the degree of cobalt extraction at pH 6 was studied. When the NaCl concentration increased from 0 to 10 g/L, the efficiency of cobalt extraction increased to 92%; when the flocculant was added and an additional stage of filtration was used, cobalt was extracted almost completely.     

Molecular behavior and synergistic effects between sodium dodecylbenzene sulfonate and Triton X-100 at oil/water interface

Significant synergistic effects between sodium dodecylbenzene sulfonate (SDBS) and nonionic nonylphenol polyethylene oxyether, Triton X-100 (TX-100), at the oil/water interface have been investigated by experimental methods and computer simulation. The influences of surfactant concentration, salinity, and the ratio of the two surfactants on the interfacial tension were investigated by conventional interfacial tension methods. A dissipative particle dynamics (DPD) method was used to simulate the adsorption properties of SDBS and TX-100 at the oil/water interface. The experiment and simulation results indicate that ultralow (lower than 10(-3) mN m(-1)) interfacial tension can be obtained at high salinity and very low surfactant concentration. Different distributions of surfactants in the interface and the bulk solution corresponding to the change of salinity have been demonstrated by simulation. Also by computer simulation, we have observed that either SDBS or TX-100 is not distributed uniformly over the interface. Rather, the interfacial layer contains large cavities between SDBS clusters filled with TX-100 clusters. This inhomogeneous distribution helps to enhancing our understanding of the synergistic interaction of the different surfactants. The simulation conclusions are consistent with the experimental results.     

The influence of chain length and electrolyte on the adsorption kinetics of cationic surfactants at the silica-aqueous solution interface

The equilibrium and kinetic aspects of the adsorption of alkyltrimethylammonium surfactants at the silica-aqueous solution interface have been investigated using optical reflectometry. The effect of added electrolyte, the length of the hydrocarbon chain, and of the counter- and co-ions has been elucidated. Increasing the length of the surfactant hydrocarbon chain results in the adsorption isotherm being displaced to lower concentrations. The adsorption kinetics indicate that above the cmc micelles are adsorbing directly to the surface and that as the chain length increases the hydrophobicity of the surfactant has a greater influence on the adsoption kinetics. While the addition of 10 mM KBr increases the CTAB maximal surface excess, there is no corresponding increase for the addition of 10 mM KCl to the CTAC system. This is attributed to the decreased binding efficiency of the chloride ion relative to the bromide ion. Variations in the co-ion species (Li, Na, K) have little effect on the adsorption rate and surface excess of CTAC up to a bulk electrolyte concentration of 10 mM. However, the rate of adsorption is increased in the presence of electrolyte. Slow secondary adsorption is seen over a range of concentrations for CTAC in the absence of electrolyte and importantly in the presence of LiCl; the origin of this slow adsorption is attributed to a structural barrier to adsorption.     

Exchange mechanisms for sodium dodecyl sulfate micelles: high salt concentration

Solute exchange experiments for the pyrene-labeled triglyceride TG-Py solubilized in sodium dodecyl sulfate (SDS) micelles in the presence and absence of salt show that the "observed" rate constant k(obs) for solute exchange varies by over 6 orders of magnitude as the free sodium ion concentration [Na(+)](aq) is varied between 10 and 850 mM. There is a sharp break in the log-log plot of k(obs) versus [Na(+)](aq) in the range of [Na(+)](aq) = 200 mM, with the exchange rate showing a weaker dependence on [Na(+)](aq) above this concentration. Up to 100 mM added NaCl, this exchange takes place essentially exclusively by a micelle fission mechanism in which each submicelle carries off one of the solutes. At higher salt concentrations, a bimolecular process becomes increasingly important. This fusion process, which involves formation of a transient supermicelle followed by fission back to two normal micelles, becomes the dominant process at high salt concentrations. The fission rate appears to level off for salt concentrations above 300-400 mM. These fission and fusion processes are related in an intimate way to the changes in the size and shape of the SDS micelles with increasing salt concentration.