Effects of surfactants on emulsification and secondary structure of lysozyme in aqueous solutions

This paper reports our investigations on the secondary structure of lysozyme in aqueous solution with D₂O and comparing systems emulsified with ionic and non-ionic amphiphiles, respectively. The opposite effect of concentration of surfactants on the lysozyme aqueous system was studied and the activity of lysozyme by the turbidimetric assay with different kinds of surfactant was compared. The effect of different surfactants on emulsification volume formed was observed and discussed. The different interactive patterns between lysozyme and ionic and non-ionic surfactants, such as sodium dodecyl sulfate (SDS), cetyl trimethyl ammonium bromide (CTAB) and Triton-X100 (Isooctoylphenoxypolyethoxy ethanol), respectively, was studied with FTIR. A simple relationship between the secondary structure and denaturation of protein is given for the emulsification of lysozyme in aqueous solutions. It is important for understanding the stabilization and avoiding the emulsions in the extraction process that the interactions between the proteins and surfactants which leads to the formation of such complexes are characterized. The utility of surfactants as a de-emulsifying agent for the commercial process to extract penicillin G from the filtrate of fermentation broth was consistent with these results.     

Influence of Surfactant Type and Concentration on Electrospinning of Chitosan–Poly(Ethylene Oxide) Blend Nanofibers

Electrospun blend nanofibers were fabricated from chitosan (1,000 kDa, 80% DDA) and poly(ethylene oxide) (PEO; 900 kDa) at a ratio of 3:1 dispersed in 50% and 90% acetic acid. The influence of surfactants on the production of electrospun nanofibers was investigated by adding nonionic polyoxyethylene glycol dodecyl ether (Brij 35), anionic sodium dodecyl sulfate, or cationic dodecyl trimethyl ammonium bromide below, at, and above their specific critical micellar concentration to the polymer blend solution. Viscosity, conductivity, and surface tension of polymer solutions, as well as morphology and composition, of nanofibers containing surfactants were determined. Pure chitosan did not form fibers and was instead deposited as beads. Addition of PEO and an increasing concentration of surfactants induced spinnability and yielded larger fibers with diameters ranging from 10 to 240 nm. Surfactants affected morphology yielding needle-like, smooth, or beaded fibers. Compositional analysis revealed that nanofibers consisted of both polymers and surfactants with concentration of the constituents in nanofibers differing from that in polymer solutions. Results suggest that surfactants may modulate polymer–polymer interactions thus influencing the morphology and composition of deposited nanostructures.     

Effect of various surfactants (cationic,anionic and non-ionic) on the growth of <Emphasis Type="Italic">Aspergillus parasiticus</Emphasis> (NRRL 2999) in relation to aflatoxin production

The effect of surfactants (two cationic, one anionic and three non-ionic) at 0.001, 0.01, 0.1 and 1.0 % concentrations on aflatoxin production, ergosterol content and sugar consumption by Aspergillus parasiticus (NRRL 2999) in YES liquid culture medium is reported. At 0.01% concentration, the cationic surfactants, cetyl dimethyl ammonium bromide (CDAB) and dodecyl trimethyl ammonium bromide (DTAB), and the anionic surfactant, sodium dodecyl sulfate (SDS), completely inhibited spore germination, while DTAB also inhibited the production of ergosterol and toxin (p < 0.05). At a concentration of 0.001%, CDAB was found to enhance toxin production, while SDS was found to inhibit it when compared with other surfactants. Non-ionic surfactants, polyoxyethylene sorbitan monolaurate (Tween-20), polyoxyethylene lauryl ether (Brij-35) and ethoxylated p-tert-octylphenol (Triton X-100) delayed the spore germination up to day 5 at all concentrations and inhibited toxin and ergosterol production at 0.001% concentration. The affect was found to be dose-dependent from 0.001% to 1%, for Triton X-100 only. Positive correlation between ergosterol content and toxin production in the presence of different surfactants at various time periods (3, 5, 7, 9 and 12 days) was found. Tween-20 was most effective in inhibiting toxin production on day 7, when aflatoxin production was found to be maximal in control group. Sugar consumption was directly proportional to the ergosterol content, showing a significant correlation with aflatoxin production.     

Spontaneous formation of DPPC monolayers at aqueous/vapor interfaces and the impact of charged surfactants

Surface tensiometry and vibrational sum-frequency spectroscopy were used to examine the structure and organization in phospholipid monolayers at the aqueous/vapor interface in the absence and in the presence of simple, charged surfactants. 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) was the phospholipid employed in these studies and surfactants included sodium dodecyl sulfate (SDS) and dodecyl trimethyl ammonium bromide (DTAB). DPPC spontaneously spreads on a pure water (pH = 5.5) surface to form monolayers as evidenced by an equilibrium spreading pressure (ESP) of 7.9 ± 2.3 mN/m and a clearly resolved vibrational spectrum. Low concentrations of surfactants inhibit the spreading of DPPC and result in significantly lower ESP values. Anionic and cationic surfactants at higher concentrations have opposite effects on monolayer organization; SDS creates well-organized monolayers while DTAB leads to poor organization of lipid molecules. Surface-specific vibrational spectra showed that high concentrations of charged surfactants (≥ 100 µM) lead to accumulation of net surface charges as evidenced by destructive and constructive interferences. Selectively deuterating surfactants results in changes in vibrational band intensities and phases enabling assignment of relative orientations of equivalent functional groups belonging to the lipid and surfactant.     

Influence of coprecipitation and interactions with anionic surfactants on the activity of plant phospholipase D.

The effects of two surfactants (sodium dodecyl sulfate and sodium dodecyl dioxyethylene sulfate) of similar structure but differing water solubility (of their calcium salts) on the enzymatic activity of cabbage phospholipase D have been studied. The solubility difference is insignificant because the two surfactants activate phospholipase D similarly. To elucidate the mechanism of their influence on the enzyme, the phase behavior in the reaction media and the interactions of the surfactants with the enzyme were investigated by potentiometry and by light scattering and UV spectroscopy. Calcium dodecyl dioxyethylene sulfate (which is more soluble in water than calcium dodecyl sulfate) precipitates in the presence of phosphatidylcholine, the substrate of the enzymatic reaction. In the reaction media phospholipase D was involved into a precipitate consisting of calcium salts of the surfactants and phosphatidylcholine that might be interpreted as its immobilization. In addition, the surfactants were adsorbed on the enzyme, unfolding the globular enzyme molecule due to electrostatic repulsion between adsorbed surfactant anions. The observed increase in the functional activity of phospholipase D is accounted for by transfer to an optimal tertiary structure for the enzyme molecule in the course of consecutive conformational transitions induced by the surfactants.     

Characterization of dewatering process of activated sludge assisted by cationic surfactants

In this work, the dewatering of activated sludge assisted by cationic surfactants was investigated. Dose of dodecyl trimethyl ammonium bromide (DTAB) and cetyl trimethyl ammonium bromide (CTAB) resulted in the release of extracellular polymeric substances (EPS) from sludge and decrease in sludge negative charge. The surfactants significantly promoted sludge dewaterability, as reflected by decreased specific resistance of filtration (SRF) and water content in sludge cakes. The treated sludge were analyzed by combined use of differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) analysis. CTAB was found more effective in releasing bound water from sludge than DTAB, due to its superior surface activity and strong adsorption/bridge capacities with sludge. The specific surface area and pore size of sludge cakes declined after surfactant treatment, indicating an enhanced compressibility. With these results, the surfactant-assisted dewatering mechanism could be attributed to the integrated effects of electrostatic neutralization, enhanced compaction and release of EPS and bound water. Our study clearly characterizes the accelerated dewatering process assisted by cationic surfactants, and demonstrates that cationic surfactants could be used as a potential agent for sludge dewatering.     

转基因食品DNA提取研究进展

为了满足消费者对转基因食品的知情权,建立准确、快速、高效的转基因成分检测技术至关重要,而高质量DNA模板的获取,是转基因食品进行基因检测的前提.对近几年来国内外转基因食品DNA提取方法:十六烷基三甲基溴化铵(hexadecyl trimethyl ammonium bromide,CTAB)法、十二烷基硫酸钠(dode...     

阴阳离子表面活性剂对无花果叶中有效成分提取工艺优化及初步功能评价

对阴阳离子复配型表面活性剂联合微波辅助提取无花果叶中有效活性物质的实验条件进行了设计和工艺参数的优化，最终的结果如下：1%（w/v）阴阳离子复配型表面活性剂，提取温度40℃，提取时间10 min，液固比30：1 mL·g^-1。在上述优化的条件下补骨脂素及佛手柑内酯的平均提取率分别为15.37和3.59 mg·g^-1。通过将利用表面活性剂辅助提取与常规水溶液提取获得的无花果叶粗提物进行对比发现，加入了表面活性剂的溶液抗氧化能力有明显增强，同时无花果叶主要物质的降解也得到显著的抑制，对植物中天然有效目标产物的绿色高效提取以及功能评价具有十分重要的理论指导意义。     

Utilization of zeolite Y in the removal of anionic,cationic and nonionic detergents during purification of proteins

Summary Hydrophobie zeolite Y was used to adsorb detergents from protein solutions and within one minute the commonly used detergents sodium dodecyl sulfate, cetyl trimethyl ammonium bromide, and Triton X-100 at concentrations of 10 mg/ml were adsorbed to a level below their critical micelle concentrations. From the detergent depleted solutions 77 to 85 % of the proteins were recovered; the lower value was obtained with protein concentration below one mg/ml.     

Determination of surfactants by use of acid phosphatase.

A new method is described for the microdetermination of anionic and cationic surfactants. Anionics can be determined by measuring the degree of their inhibition of enzyme activity (inhibition method). On the other hand, cationics are determined by a method utilizing the finding that the original inhibition of a potent inhibitor previously added to a substrate solution is suppressed by the addition of small amount of cationics (suppression method). In this study, the enzyme is acid phosphatase and p-nitrophenyl phosphate is used as substrate. Employing the method described above, 5–50 ppm of alkylbenzene sulfonate (ABS), 10–90 ppm of sodium dodecyl sulfate (SDS) and 5–15 ppm of dodecyl trimethyl ammonium chloride and dodecyl pyridinium chloride can be determined. The procedure is relatively simple and the analysis requires only 4–5 min.     

Comparative effects of four surfactants on growth,contraction and adhesion of cultured human fibroblasts

A range of surfactants, including the anionic sodium dodecyl sulfate, the cationic cetyltrimethylammonium bromide and the nonionics octylphenoxy polyethoxyethanol (Triton X100) and polyoxyethylene 20 sorbitan monoleate (Tween 80) was studied for effects on proliferation, contractibility and attachment of cultured human fibroblasts. Only ionic surfactants exhibited a stimulatory effect on fibroblast proliferation, whereas all the surfactants tested increased the contraction of collagen gels containing fibroblasts, with the greatest effect from the non-ionic surfactants. This activity was not correlated with an increase of cell population or cell attachment within the collagenous matrix. The activity of the surfactants was seen only at levels close to their LD₅₀ values and in a narrow range of concentrations. Thus, we consider that they are the result of the so-called hormesis phenomenon.Abbreviations CTAB cetyltrimethyl-ammonium bromide - FCS fetal calf serum - LD₁₀₀ dose lethal to 100% of exposed - MCD maximal contraction dose - PDL population doubling level - SDS sodium dodecyl sulfate     

Fluorimetric studies on the binding of 4-(dimethylamino)cinnamic acid with micelles and bovine serum albumin

The constrained photophysics of intramolecular charge transfer (ICT) probe 4-(dimethylamino)cinnamic acid (DMACA) was studied in different surfactant systems as well as in presence of model water soluble protein bovine serum albumin (BSA). Binding of the probe in ionic micelles like sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) causes an increase in ICT fluorescence intensity, whereas, in non-ionic TritonX-100 (TX-100) the intensity decreases with a concomitant increase in emission from locally excited (LE) state. The observations were explained in terms of the different binding affinity, location of the probe and also the nature of specific hydrogen bonding interaction in the excited state nonradiative relaxation process of DMACA. The ICT fluorescence emission yield decreases in BSA due to the locking in of the probe buried in the hydrophobic pocket of the protein structure. SDS induced uncoiling of protein and massive cooperative binding between BSA and SDS is manifested by the release of probe molecules in relatively free aqueous environment.     

Surfactant-induced lipid peroxidation in a tropical euryhaline teleost Oreochromis mossambicus (Tilapia) adapted to fresh water

Exposure to anionic (sodium dodecyl sulfate, SDS), cationic (cetyl trimethyl ammonium bromide CTAB) and non ionic (Triton X-100) surfactants at a sub lethal concentration of 1 ppm resulted in severe oxidative stress in the hepatic, renal and cardiac tissues of fresh water adapted Oreochromis mossambicus. Hepatic catalase showed significant increase (P<0.001) in all the surfactant exposed fish, but the renal enzyme was significantly increased only in CTAB dosed fish (P<0.001) and the cardiac enzyme showed significant increase in Triton (P<0.05) and CTAB dosed fish (P<0.001). SOD levels were significantly increased (P<0.001) in hepatic, renal and cardiac tissues of all the surfactant-treated fish. Glutathione reductase also was significantly increased (P<0.001) in the hepatic and renal tissues of surfactant dosed fish except cardiac tissues of CTAB exposed animals. Glutathione levels in the tissues studied were significantly higher in the surfactant treated animals (P<0.001) whereas malondialdehyde levels were significantly elevated only in the hepatic tissues of animals exposed to Triton (P<0.001). The surfactants based on their charge, antioxidant profile and in vivo metabolism may be arranged in the order of decreasing toxicity as CTAB > Triton > SDS. Thus it may be inferred from the present study that the antioxidant defenses and the in vivo metabolism of the surfactants are key factors in deciding the surfactant toxicity.     

Studies on surfactant-biopolymer interaction. I. Microcalorimetric investigation on the interaction of cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) with gelatin (Gn), lysozyme (Lz) and deoxyribonucleic acid (DNA)

The interaction of the surfactants cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) with the biopolymers gelatin (Gn), lysozyme (Lz) and deoxyribonucleic acid (DNA) was studied by isothermal titration microcalorimetry at varied biopolymer concentration, pH and temperature. The nature of interaction of the surfactants with the biopolymers was assessed from the observed enthalpy-[surfactant] profiles. The biopolymer-induced aggregation of the surfactants was observed. The enthalpies of aggregation of amphiphiles, binding of aggregates with macromolecules, organisational change of bound aggregates, and threshold concentrations for micelle formation of surfactants in the presence of biopolymers were estimated. The results collected on the three biopolymers were analysed and compared.     

Inactivation and reactivation of mitochondrial respiration by charged detergents

Respiration of submitochondrial preparations can be inhibited by the cationic detergent cetyl trimethyl ammonium bromide and the anionic detergent sodium dodecyl sulfate in the range of 0.3–2 μmol of detergent per mg of mitochondrial membrane protein depending on the substrate and detergent used. This inhibition can be rapidly reversed by neutralizing a given detergent by the detergent of the opposite charge. At higher levels of the inhibiting detergent, no such reactivation was observed. Spin labeling assays of membrane structure were used to correlate structural effects with the loss and recovery of respiratory functions.Because the detergents progressively disrupt membrane structure, mitochondria were cross-linked with bifunctional imidoesters to an extent that osmotic properties and detergent lysis were gone, but respiration remained. Such fixed respiring mitochondria also show inhibition reactivation phenomena.     

Inactivation and reactivation of mitochondrial respiration by charged detergents.

Respiration of submitochondrial preparations can be inhibited by the cationic detergent cetyl trimethyl ammonium bromide and the anionic detergent sodium dodecyl sulfate in the range of 0.3-2 mumol of detergent per mg of mitochondrial membrane protein depending on the substrate and detergent used. This inhibition can be rapidly reversed by neutralizing a given detergent by the detergent of the opposite charge. At higher levels of the inhibiting detergent, no such reactivation was observed. Spin labeling assays of membrane structure were used to correlate structural effects with the loss and recovery of respiratory functions. Because the detergents progressively disrupt membrane structure, mitochondrial were cross-linked with bifunctional imidoesters to an extent that osmotic properties and detergent lysis were gone, but respiration remained. Such fixed respiring mitochondria also show inhibition reactivation phenomena.     

Effect of additives on mass transfer in turbine aeration

Mass transfer coefficients and interfacial areas were determined for the aeration of aqueous solutions in a turbine agitated vessel. The mass transfer coefficients measured for water without additive and for sodium chloride solutions matched very well to measurements in the literature for air bubbles of the same diameter in free rise. Thus the only effect of agitation was to determine the bubble size which then in turn set the coefficient. Two surface active agents were studied: sodium dodecyl sulfate and Dow Corning Antifoam C. The rate of mass transfer increased with the former additive but decreased with the latter; however, the mass transfer coefficient was the exact same function of bubble diameter in both cases and the different rates are attributed to the quite different effects on interfacial area.     

Evaluation of the Effect of Surfactants on the Movement of Pesticides in Soils Using a Soil Thin-Layer Chromatography Technique

In this study, the effect of concentration (1/2 CMC, at CMC and 2 x CMC) of surfactants, cetyl trimethyl ammonium bromide (cationic), sodium dodecyl sulfate (anionic), and tween ‘20’ (non-ionic) on the movement of carbofuran, chlorpyrifos and en-dosulfan in soils was evaluated by using a soil thin-layer chromatographic technique. The movement of pesticides was detected by spray reagents and expressed in terms of Rf values. The penetrability K was found to increase by decreasing the plate angle and followed the order as: sandy loam > loam > silt loam soils. The penetrability K also decreases in surfactant-free and surfactant-amended soils when developed in distilled water and aqueous surfactant solutions of different CMCs, respectively. The higher movement of pesticides was observed in sandy loam soil followed by loam and silt loam soils. On the basis of Rf values, the movement of pesticides follows the order as: carbofuran > chlorpyrifos > endosulfan, both in surfactant-amended and surfactant-free soils when developed in distilled water and aqueous surfactant solutions of different CMCs. The movement is directly proportional to the aqueous solubilities, polarities, and carbon numbers and inversely related to the molecular weights of pesticides. A significant increase or decrease of pesticides movement in soils was discussed on the basis of adsorption of pesticides on soils, chemical nature of the surfactants, and its concentrations in terms of critical micelle concentrations (CMCs) in soils and eluents. Results obtained may provide insights pertaining to the use of surfactants for solving soil pollution problems posed by pesticides.     

Study of inclusion complexes of cycloamylose with surfactants by isothermal titration calorimetry

Useful materials can be made from cycloamylose (CA) and the functional properties of CA could be improved by complexation with surfactants. Isothermal titration calorimetry (ITC) was used to investigate interactions between CA and surfactants in buffered solutions. Three surfactants with C₁₂ non-polar tail groups and charged [anionic: sodium dodecyl sulfate (SDS); cationic: dodecyl trimethylammonium bromide (DTAB)] or non-charged headgroups [non-ionic: polyoxyethylene 23 lauryl ether (Brij35)] were used in this study. The effects of temperature, pH, and salt concentration were also studied. All three surfactants bound to CA; however, Brij35 binding to CA was negligible. Enthalpy changes associated with binding of surfactants to CA were exothermic except for interactions measured at 50 °C. There was no effect of pH on surfactant demicellization or CA binding. Salt concentration affected surfactant demicellization, but the amount of SDS bound to CA at saturation was unaffected by salt. When the titration curves obtained for CA with SDS and DTAB were fitted, it could be analyzed using a model based on a single set of identical sites.     

Photophysical and photodynamic properties of Pyronin Y in micellar media at different temperatures

In this study, photophysics and photodynamical properties of Pyronin Y (PyY) in different liquid media were investigated. Interactions of PyY, which is a positively charged pigment compound pertaining to the xanthene derivatives with surfactants possessing distinct charges, were determined by using the molecular absorption and fluorescence spectroscopy techniques. It was observed that band intensities of absorption and fluorescence spectra belonging to PyY increase in proportion to the water when compared to three micelle systems, cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and Triton X‐100 (TX‐100). This suggests that interactions in micelle systems are different from those in deionized water, and solvation and surface interactions modify. It is determined that the strongest interaction occurs between PyY dye and SDS, anionic surfactant, and this interaction arises from the electrostatic forces. Calculated photophysical parameters indicated that the microenvironment of PyY in SDS micelle is different to that of other systems. In temperature studies, it was reported that increasing the temperature of the samples increased non‐radiative transitions. Steady‐state fluorescence anisotropy values were calculated by using fluorescence intensities of PyY compound in pre‐micellar, micellar and post‐micellar systems. Once the PyY fluorescence probe is added to the surfactant containing solutions below the critical micelle concentrations, the measured anisotropy values were found to be low because the probe remains in the deionized water phase. When the surfactant concentration of the medium becomes closer to the critical micelle concentrations, the steady‐state anisotropy value prominently increases. This is because of the restrictions on the rotational diffusion of the probe in micellar solution. It is observed that positively charged PyY shows a higher affinity to the negatively charged SDS compared with the positively charged CTAB and neutral TX‐100 surfactants. This can be explained by Coulombic interactions.