Zeitschriftenartikel: „Surfactant aggregate“

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Veldhuizen, R. A., S. A. Hearn, J. F. Lewis und F. Possmayer. „Surface-area cycling of different surfactant preparations: SP-A and SP-B are essential for large-aggregate integrity“. Biochemical Journal 300, Nr. 2 (01.06.1994): 519–24. http://dx.doi.org/10.1042/bj3000519.

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Surface-area cycling is an in vitro procedure for the conversion of large into small surfactant aggregates. In this procedure a tube containing a surfactant suspension is rotated end-over-end at 37 degrees C so that the surface area of the suspension changes twice each cycle. We have utilized this method to study the mechanisms involved in aggregate conversion. Several different surfactant preparations were analysed: (1) bovine natural surfactant, a sucrose-gradient-purified material containing surfactant phospholipid and surfactant-associated proteins (SP-) SP-A, SP-B and SP-C; (2) bovine lipid-extract surfactant, which contains the surfactant phospholipids and SP-B and SP-C; (3) mixtures of dipalmitoyl phosphatidylcholine and phosphatidylglycerol (7:3, w/w) reconstituted with one or more surfactant proteins. Aggregate conversion was measured by phosphorus analysis of a 40,000 g supernatant (small aggregate) and pellet (large aggregates) before and after surface-area cycling. Surface-area cycling of lipid extract surfactant or lipids plus SP-B or SP-C resulted in rapid aggregate conversion. Lipids alone were not converted. Only a small percentage of purified natural surfactant was converted into small aggregates. Addition of SP-A to lipid extract surfactant could inhibit aggregate conversion of this material, but this was only observed when an additional 1% (w/w) of SP-B was added to the lipid extract. It is concluded that SP-A is important for large-aggregate integrity. It appears that SP-A acts in conjunction with SP-B. The presence of SP-B and/or SP-C is required for aggregate conversion; it is proposed that this reflects the necessity for lipid adsorption in aggregate conversion.

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Veldhuizen, R. A., J. Marcou, L. J. Yao, L. McCaig, Y. Ito und J. F. Lewis. „Alveolar surfactant aggregate conversion in ventilated normal and injured rabbits“. American Journal of Physiology-Lung Cellular and Molecular Physiology 270, Nr. 1 (01.01.1996): L152—L158. http://dx.doi.org/10.1152/ajplung.1996.270.1.l152.

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Alveolar surfactant can be separated into two subtypes; large aggregates and small aggregates. Large aggregates represent the surface active form of surfactant and are the metabolic precursors of small aggregates. Previous studies examined the mechanism by which large aggregates are converted into small aggregates in vitro. We used intratracheal injection of radiolabeled large aggregates in rabbits to probe the aggregate conversion in vivo. After this injection, animals were mechanically ventilated for 60 min. After the animals were killed, the lungs were lavaged, and the percentage of radiolabel present in the small aggregate fraction was determined. Our results showed that ventilation resulted in aggregate conversion and that increases in tidal volume, but not in respiratory rate, correlated with increased conversion. Aggregate conversion in rabbits with acute lung injury correlated significantly with severity of injury. We conclude that a change in surface area (i.e., respiration) is necessary for aggregate conversion in vivo and that the ventilation strategy can affect this conversion. Furthermore, increased aggregate conversion in injured lungs might contribute to increased small-to-large aggregate ratios in these lungs compared with normal lungs.

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Paul, Nawal K., Tyler Mercer, Hussein Al-Mughaid, D. Gerrard Marangoni, Michael J. McAlduff, Kulbir Singh und T. Bruce Grindley. „Synthesis and properties of multiheaded and multitailed surfactants based on tripentaerythritol“. Canadian Journal of Chemistry 93, Nr. 5 (Mai 2015): 502–8. http://dx.doi.org/10.1139/cjc-2014-0342.

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The surface and self-assembly properties of a family of multiheaded, multitailed surfactants based on a tripentaerythritol backbone are described. Critical aggregation concentrations of these unusual surfactant systems have been determined from surface tension measurements; aggregate sizes in the presence and absence of a small amount of added electrolyte have been obtained via dynamic light scattering, and the morphologies of the aggregates were examined from electron microscopy measurements. In general, when compared to conventional ionic and two-headed surfactants (and other recently synthesized pentaerythritol derived surfactants from this group), these multiheaded surfactants exhibited some unusual trends in their aggregation behaviour and interesting aggregate structures in aqueous solution, as a function of alkyl chain length.

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Chavez-Martinez, E. H., E. Cedillo-Cruz und H. Dominguez. „Adsorption of metallic ions from aqueous solution on surfactant aggregates: a molecular dynamics study“. Condensed Matter Physics 24, Nr. 2 (2021): 23601. http://dx.doi.org/10.5488/cmp.24.23601.

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Metallic ion adsorption on surfactant aggregates were studied with Molecular dynamics simulations. Using ionic salts, such as lead sulfate (PbSO4) and aluminum sulfate [Al2(SO4)3], adsorption of lead and aluminum were investigated at different salt concentrations and different surfactant aggregates (micelles) sizes. The micelles were constructed with spherical shapes composed of sodium dodecyl sulfate (SDS) anionic surfactants. The electrostatic interactions between the positive ions and the negative SDS headgroups promote capture of the metal particles on the aggregate surface. Metal adsorption was analyzed in terms of radial density profiles, partial pair distribution functions and adsorption isotherms. It is showed that SDS micelles adsorb better lead than aluminum ions regardless of the size of the aggregates and salt concentrations.

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Ikegami, Machiko, Thomas R. Korfhagen, Jeffrey A. Whitsett, Michael D. Bruno, Susan E. Wert, Kazuko Wada und Alan H. Jobe. „Characteristics of surfactant from SP-A-deficient mice“. American Journal of Physiology-Lung Cellular and Molecular Physiology 275, Nr. 2 (01.08.1998): L247—L254. http://dx.doi.org/10.1152/ajplung.1998.275.2.l247.

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Mice that are surfactant protein (SP) A deficient [SP-A(−/−)] have no apparent abnormalities in lung function. To understand the contributions of SP-A to surfactant, the biophysical properties and functional characteristics of surfactant from normal [SP-A(+/+)] and SP-A(−/−) mice were evaluated. SP-A-deficient surfactant had a lower buoyant density, a lower percentage of large-aggregate forms, an increased rate of conversion from large-aggregate to small-aggregate forms with surface area cycling, increased sensitivity to inhibition of minimum surface tension by plasma protein, and no tubular myelin by electron microscopy. Nevertheless, large-aggregate surfactants from SP-A(−/−) and SP-A(+/+) mice had similar adsorption rates and improved the lung volume of surfactant-deficient preterm rabbits similarly. Pulmonary edema and death caused by N-nitroso- N-methylurethane-induced lung injury were not different in SP-A(−/−) and SP-A(+/+) mice. The clearance of125I-labeled SP-A from lungs of SP-A(−/−) mice was slightly slower than from SP-A(+/+) mice. Although the absence of SP-A changed the structure and in vitro properties of surfactant, the in vivo function of surfactant in SP-A(−/−) mice was not changed under the conditions of these experiments.

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Veldhuizen, R. A., Y. Ito, J. Marcou, L. J. Yao, L. McCaig und J. F. Lewis. „Effects of lung injury on pulmonary surfactant aggregate conversion in vivo and in vitro“. American Journal of Physiology-Lung Cellular and Molecular Physiology 272, Nr. 5 (01.05.1997): L872—L878. http://dx.doi.org/10.1152/ajplung.1997.272.5.l872.

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Within the alveolar space pulmonary surfactant is converted from the surface active large aggregates (LA) to the inactive small aggregates (SA). This conversion is affected by a change in surface area, lung injury, breathing pattern, and protease activity. This study examined the effect of N-nitroso-N-methylurethane-induced acute lung injury on aggregate conversion in mechanically ventilated and spontaneously breathing rabbits. Both the in vitro surface area cycling techniques and the in vivo technique of intratracheally injecting radiolabeled LA were used for analyzing aggregate conversion. Mechanical ventilation of injured lungs resulted in increased aggregate conversion and increased surfactant aggregate ratios compared with controls. Spontaneously breathing injured animals had aggregate conversion and aggregate ratios that were not significantly different from controls. In vitro aggregate conversion was slower for LA obtained from injured animals compared with normal animals. We conclude that the mechanical stress of mechanical ventilation results in increased aggregate conversion and aggregate ratios. Furthermore, in vitro conversion of isolated LA does not necessarily reflect the conversion of aggregates within the alveoli.

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Madsen, Jens, Gunna Christiansen, Lise Giehm und Daniel Otzen. „Release of Pharmaceutical Peptides in an Aggregated State: Using Fibrillar Polymorphism to Modulate Release Levels“. Colloids and Interfaces 3, Nr. 1 (26.03.2019): 42. http://dx.doi.org/10.3390/colloids3010042.

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Traditional approaches to achieve sustained delivery of pharmaceutical peptides traditionally use co-excipients (e.g., microspheres and hydrogels). Here, we investigate the release of an amyloidogenic glucagon analogue (3474) from an aggregated state and the influence of surfactants on this process. The formulation of peptide 3474 in dodecyl maltoside (DDM), rhamnolipid (RL), and sophorolipid (SL) led to faster fibrillation. When the aggregates were subjected to multiple cycles of release by repeated resuspension in fresh buffer, the kinetics of the release of soluble peptide 3474 from different surfactant aggregates all followed a simple exponential decay fit, with half-lives of 5–18 min and relatively constant levels of release in each cycle. However, different amounts of peptide are released from different aggregates, ranging from 0.015 mg/mL (3475-buffer) up to 0.03 mg/mL (3474-DDM), with 3474-buffer and 3474-RL in between. In addition to higher release levels, 3474-DDM aggregates showed a different amyloid FTIR structure, compared to 3474-RL and 3474-SL aggregates and a faster rate of degradation by proteinase K. This demonstrates that the stability of organized peptide aggregates can be modulated to achieve differences in release of soluble peptides, thus coupling aggregate polymorphism to differential release profiles. We achieved aggregate polymorphism by the addition of different surfactants, but polymorphism may also be reached through other approaches, including different excipients as well as changes in pH and salinity, providing a versatile handle to control release profiles.

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Veldhuizen, R. A. W., K. Inchley, S. A. Hearn, J. F. Lewis und F. Possmayer. „Degradation of surfactant-associated protein B (SP-B) during in vitro conversion of large to small surfactant aggregates“. Biochemical Journal 295, Nr. 1 (01.10.1993): 141–47. http://dx.doi.org/10.1042/bj2950141.

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Pulmonary surfactant obtained from lung lavages can be separated by differential centrifugation into two distinct subfractions known as large surfactant aggregates and small surfactant aggregates. The large-aggregate fraction is the precursor of the small-aggregate fraction. The ratio of the small non-surface-active to large surface-active surfactant aggregates increases after birth and in several types of lung injury. We have utilized an in vitro system, surface area cycling, to study the conversion of large into small aggregates. Small aggregates generated by surface area cycling were separated from large aggregates by centrifugation at 40,000 g for 15 min rather than by the normal sucrose gradient centrifugation. This new separation method was validated by morphological studies. Surface-tension-reducing activity of total surfactant extracts, as measured with a pulsating-bubble surfactometer, was impaired after surface area cycling. This impairment was related to the generation of small aggregates. Immunoblot analysis of large and small aggregates separated by sucrose gradient centrifugation revealed the presence of detectable amounts of surfactant-associated protein B (SP-B) in large aggregates but not in small aggregates. SP-A was detectable in both large and small aggregates. PAGE of cycled and non-cycled surfactant showed a reduction in SP-B after surface area cycling. We conclude that SP-B is degraded during the formation of small aggregates in vitro and that a change in surface area appears to be necessary for exposing SP-B to protease activity.

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Liu, Z., D. A. Edwards und R. G. Luthy. „Nonionic Surfactant Sorption onto Soil“. Water Science and Technology 26, Nr. 9-11 (01.11.1992): 2337–40. http://dx.doi.org/10.2166/wst.1992.0731.

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Experiments in batch soil/aqueous systems were conducted to evaluate the sorption onto soil of four nonionic surfactants. At bulk solution surfactant concentration less than the respective critical micelle (aggregate) concentration (CMC or CAC), sorption can be assessed using a surface tension technique and can be characterized with a Freundlich isotherm. At bulk solution surfactant concentrations equal to or greater than the critical concentration, sorption of the micelle-forming surfactants can be assessed by a spectrophotometric technique with an azo dye and had a constant value; sorption of the lamellae-forming surfactant can be assessed by a chemical oxidation technique and, however, appeared to be an increasing function of the surfactant dose.

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VELDHUIZEN, Ruud A. W., Li-Juan YAO, Stephen A. HEARN, Fred POSSMAYER und James F. LEWIS. „Surfactant-associated protein A is important for maintaining surfactant large-aggregate forms during surface-area cycling“. Biochemical Journal 313, Nr. 3 (01.02.1996): 835–40. http://dx.doi.org/10.1042/bj3130835.

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Alveolar surfactant can be separated into two major subfractions, the large surfactant aggregates (LAs) and the small surfactant aggregates (SAs). The surface-active LAs are the metabolic precursors of the inactive SAs. This conversion of LAs into SAs can be studied in vitro using a technique called surface-area cycling. We have utilized this technique to examine the effect of trypsin on aggregate conversion. Our results show that trypsin increases the conversion of LAs into SAs in a concentration- and time-dependent manner. Immunoblot analysis revealed that surfactant-associated Protein A (SP-A) was the main target of trypsin. To examine further the role of SP-A in aggregate conversion, we tested the effect of Ca2+ and mannan on this process. The absence of Ca2+ (1 mM EDTA) and the presence of mannan both increased the formation of SAs. Electron microscopy revealed that highly organized multilamellar and tubular myelin structures were present in samples that converted slowly to SAs. We concluded that SP-A is important for maintaining LA forms during surface-area cycling by stabilizing tubular myelin and multilamellar structures.

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Lewis, J. F., M. Ikegami und A. H. Jobe. „Altered surfactant function and metabolism in rabbits with acute lung injury“. Journal of Applied Physiology 69, Nr. 6 (01.12.1990): 2303–10. http://dx.doi.org/10.1152/jappl.1990.69.6.2303.

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Lung injury was induced in rabbits with N-nitroso-N-methylurethane (NNNMU), and saturated phosphatidylcholine (Sat PC) pool sizes and phospholipid compositions were measured in alveolar wash subfractions isolated by differential centrifugation (large and small surfactant aggregates). Surfactant metabolism also was studied using intravascular and intratracheal radiolabels. Protein permeability, gas exchange, and compliance were significantly abnormal as lung injury progressed. At peak injury, there was a decrease in the large aggregate Sat PC pool size in alveolar wash accompanied by increased uptake of Sat PC from the air space and increased specific activity of both intravascular and intratracheal radiolabels in lamellar bodies. This was followed by a marked rise in the small aggregate pool size in the alveolar wash and increased secretion of Sat PC into the air spaces. Phospholipid compositions, total phospholipid-to-protein ratios, and in vivo functional studies using a preterm ventilated rabbit model were abnormal for both large and small aggregate surfactant fractions from the lung-injured rabbits. These studies characterize quantitative, qualitative, and functional changes of alveolarwash surfactant subfractions in NNNMU-injured lungs.

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Gradova, Margaret A., Vladimir V. Artemov und Anton V. Lobanov. „Aggregation behavior of tetraphenylporphyrin in aqueous surfactant solutions: Chiral premicellar J-aggregate formation“. Journal of Porphyrins and Phthalocyanines 19, Nr. 07 (Juli 2015): 845–51. http://dx.doi.org/10.1142/s1088424615500595.

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Porphyrin-surfactant interactions in aqueous solutions are known to result in the selfassembly of various supramolecular structures, including pigment-surfactant complexes, J- and H-aggregates, and solubilized dye species. Detailed studies on the mechanisms of the intermolecular interactions governing the above self-assembly processes allow to predict the aggregation state and hence, the photophysical properties of the dye-surfactant assemblies in order to perform a direct synthesis of the desired porphyrin-based nanostructures at the appropriate experimental conditions. This paper describes a novel example of the surfactant-induced J-aggregate formation from the diprotonated hydrophobic tetraphenylporphyrin species in submicellar aqueous anionic surfactant solutions. The above assemblies are characterized by a rod-like morphology and possess supramolecular chirality according to the CD measurements.

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Cassidy, Marta A., und Gregory G. Warr. „Steric and Counterion Effects on Cationic Surfactant Self-Assembly into Micelles and Liquid Crystals“. Australian Journal of Chemistry 56, Nr. 10 (2003): 1065. http://dx.doi.org/10.1071/ch03116.

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The roles of head-group size and counterion association on aggregate morphology in solution and lyotropic phases of cationic surfactants (tetradecyl trimethyl-, tetradecyl triethyl-, and tetradecyl tripropylammonium) are examined, using salicylate as a strongly binding counterion. Larger head groups are found to inhibit the formation of low-curvature structures such as bilayers, and salicylate binding excludes spherical micelles, so that both effects tend to favour locally cylindrical aggregates. Interfacial probes and ion flotation show that the binding of salicylate is reduced by increasing head-group size. In addition, a novel demixing is observed with features similar to lower consolute behaviour of other cationic surfactant systems.

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Horowitz, A. D., K. Kurak, B. Moussavian, J. A. Whitsett, S. E. Wert, W. M. Hull, J. McNanie und M. Ikegami. „Preferential uptake of small-aggregate fraction of pulmonary surfactant in vitro“. American Journal of Physiology-Lung Cellular and Molecular Physiology 273, Nr. 2 (01.08.1997): L468—L477. http://dx.doi.org/10.1152/ajplung.1997.273.2.l468.

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Homeostasis of pulmonary surfactant requires metabolic clearance of surfactant forms with decreased surface activity. Rabbit pulmonary surfactant was labeled in vivo with rhodamine-labeled dipalmitoylphosphatidylethanolamine (R-DPPE), isolated, and fractionated into large- and small-aggregate subfractions by differential centrifugation. Endocytosis of large (LA)- and small (SA)-aggregate surfactant by a mouse lung epithelial cell line (MLE-12) was evaluated in vitro by epifluorescence microscopy. More SA than LA surfactant was taken up by MLE-12 cells. Endocytosis of SA and LA surfactant was inhibited by preincubation of the subfractions with surfactant protein A and 3.3 mM Ca2+. The difference in uptake between SA and LA surfactant was lost for reconstituted organic extracts of the subfractions. Much of the difference in uptake of SA and LA surfactant may be attributed to the greater concentration of surfactant protein A in LA surfactant.

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Alamrew, Asres Simeneh, und Konrad Mollenhauer. „Advantages Of Filler And Surfactant Additive To Improve Moisture Sensitivity Of Hot Mix Asphalt Mixtures.“ IOP Conference Series: Materials Science and Engineering 1202, Nr. 1 (01.11.2021): 012011. http://dx.doi.org/10.1088/1757-899x/1202/1/012011.

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Abstract This research investigated the effect of mineral composition of aggregate on moisture sensitivity of bituminous mixtures and explored the benefits of hydrated lime filler and Wetfix BE surfactant additive to improve the resistance of the mix against moisture sensitivity. Basalt, quartzite, and limestone aggregates were selected based on their different mineralogy and 70 -100 penetration graded bitumen binders used during the study. Four laboratory tests the rolling bottle, shaking abrasion, pull-off tensile strength and indirect tensile strength tests were applied to study the effects of aggregate minerals and benefits of hydrated lime and Wetfix BE. Statistical analysis using Two-way ANOVA test conducted for each test to check the outcome significance. Results from each test revealed that mineral composition of aggregate have significant effects on the moisture resistance performance of bituminous mixtures and hydrated lime filler and Wetfix BE surfactant additives have advantages to improve the performance of bituminous mixture against moisture sensitivity and improves the long-term performance of asphalt mix.

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Nusselder, Jan Jaap H., und Jan B. F. N. Engberts. „Surfactant structure and aggregate morphology. The urge for aggregate stability“. Journal of the American Chemical Society 111, Nr. 13 (Juni 1989): 5000–5002. http://dx.doi.org/10.1021/ja00195a075.

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KARAPETSAS, GEORGE, RICHARD V. CRASTER und OMAR K. MATAR. „On surfactant-enhanced spreading and superspreading of liquid drops on solid surfaces“. Journal of Fluid Mechanics 670 (25.01.2011): 5–37. http://dx.doi.org/10.1017/s0022112010005495.

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The mechanisms driving the surfactant-enhanced spreading of droplets on the surface of solid substrates, and particularly those underlying the superspreading behaviour sometimes observed, are investigated theoretically. Lubrication theory for the droplet motion, together with advection–diffusion equations and chemical kinetic fluxes for the surfactant transport, leads to coupled evolution equations for the drop thickness, interfacial concentrations of surfactant monomers and bulk concentrations of monomers and micellar, or other, aggregates. The surfactant can be adsorbed on the substrate either directly from the bulk monomer concentrations or from the liquid–air interface through the contact line. An important feature of the spreading model developed here is the surfactant behaviour at the contact line; this is modelled using a constitutive relation, which is dependent on the local surfactant concentration. The evolution equations are solved numerically, using the finite-element method, and we present a thorough parametric analysis for cases of both insoluble and soluble surfactants with concentrations that can, in the latter case, exceed the critical micelle, or aggregate, concentration. The results show that basal adsorption of the surfactant plays a crucial role in the spreading process; the continuous removal of the surfactant that lies upon the liquid–air interface, due to the adsorption at the solid surface, is capable of inducing high Marangoni stresses, close to the droplet edge, driving very fast spreading. The droplet radius grows at a rate proportional to ta with a = 1 or even higher, which is close to the reported experimental values for superspreading. The spreading rates follow a non-monotonic variation with the initial surfactant concentration also in accordance with experimental observations. An accompanying feature is the formation of a rim at the leading edge of the droplet. In some cases, the drop spreads to form a ‘pancake’ or creates a ‘secondary’ front separated from the main droplet.

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Jana, Tushar, und Arun K. Nandi. „Tailoring of the self-organized structure of sulfonated polyaniline from a fibrillar network to a colloidal aggregate“. Journal of Materials Research 18, Nr. 7 (Juli 2003): 1691–97. http://dx.doi.org/10.1557/jmr.2003.0232.

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Self-organized structures of the sodium salt of sulfonated polyaniline (prepared from the leucoemeraldine base of polyaniline) in the presence of a mixture of cationic and nonionic surfactants were studied. It was used in the latex form, which has been prepared using a conventional method with sodium dodecyl sulfate. The cationic surfactant used was didodecyl dimethyl ammonium bromide, and the nonionic surfactant used was Triton-X-100. The supramolecular organization was made in aqueous medium by varying the concentrations of the components. A three-dimensional fibrillar network and colloidal aggregate were produced due to the supramolecular organization. The thermal study indicated reversible first-order phase transition in the former cases fulfilling the criteria of thermoreversible gels. A probable explanation of the different morphology from the variation of charge density on the vesicle surface has been offered. The conductivity of fibrillar network is two orders higher than that of the colloidal aggregate.

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Ikegami, Machiko, Jeffrey A. Whitsett, Alan Jobe, Gary Ross, James Fisher und Thomas Korfhagen. „Surfactant metabolism in SP-D gene-targeted mice“. American Journal of Physiology-Lung Cellular and Molecular Physiology 279, Nr. 3 (01.09.2000): L468—L476. http://dx.doi.org/10.1152/ajplung.2000.279.3.l468.

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Mice with surfactant protein (SP)-D deficiency have three to four times more surfactant lipids in air spaces and lung tissue than control mice. We measured multiple aspects of surfactant metabolism and function to identify abnormalities resulting from SP-D deficiency. Relative to saturated phosphatidylcholine (Sat PC), SP-A and SP-C were decreased in the alveolar surfactant and the large-aggregate surfactant fraction. Although large-aggregate surfactant from SP-D gene-targeted [(−/−)] mice converted to small-aggregate surfactant more rapidly, surface tension values were comparable to values for surfactant from SP-D wild-type [(+/+)] mice. 125I-SP-D was cleared with a half-life of 7 h from SP-D(−/−) mice vs. 13 h in SP-D(+/+) mice. Although initial incorporation and secretion rates for [3H]palmitic acid and [14C]choline into Sat PC were similar, the labeled Sat PC was lost from the lungs of SP-D(+/+) mice more rapidly than from SP-D(−/−) mice. Clearance rates of intratracheal [3H]dipalmitoylphosphatidylcholine were used to estimate net clearances of Sat PC, which were approximately threefold higher for alveolar and total lung Sat PC in SP-D(−/−) mice than in SP-D(+/+) mice. SP-D deficiency results in multiple abnormalities in surfactant forms and metabolism that cannot be attributed to a single mechanism.

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Yadav, Ramesh, K. Chandramani Singh, S. R. Choudhary und P. C. Jain. „Location of Phase Boundaries of Lyotropic Liquid Crystal Employing Positron Lifetime Spectroscopy and Electrical Conductivity Measurement“. Materials Science Forum 733 (November 2012): 127–31. http://dx.doi.org/10.4028/www.scientific.net/msf.733.127.

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Different compositions of surfactant systems give rise to a rich variety of structures of aggregates. At higher concentrations of surfactant in water, the surfactant molecules aggregate to form lyotropic liquid crystals [1]. In the present work we have prepared two surfactant systems consisting of (i) 20% of cetyl-trimethyl-ammonium-bromide (CTAB) in water, and (ii) 30% of tetra-decyl-trimethyl-ammonium-bromide (TTAB) in water. Both the systems exhibit various lyotropic liquid crystal structures when an increasing amount of co-surfactant is added as third component [2, 3]. These liquid crystalline structures are very sensitive to the solution conditions such as co-surfactant concentration, temperature, ionic strength, counter ion polarizability etc. In this study, positron life time spectroscopy and conductivity measurement have been employed to locate various phases exhibited by the lyotropic liquid crystals. In addition to delineating various phase boundaries of the systems, positron annihilation technique has also yielded new findings.

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Raihanah, Nadhifa, Solihudin und Rukiah. „The Effects of Surfactant on the Stability of SiO₂ nanofluid Prepared by Bead-milling Method“. Journal of Physics: Conference Series 2344, Nr. 1 (01.09.2022): 012005. http://dx.doi.org/10.1088/1742-6596/2344/1/012005.

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Abstract Typical nanofluid containing metal or non-metallic nanoparticles dispersed in water with high surface energy. This condition causes aggregation and leads to the instability of the nanofluid dispersion in media. The inclusion of surfactants during the bead-milling process can increase the amount of dispersion stability of nanofluids with bigger particle sizes. The aim of this study was to determine the optimum surfactant in stabilizing SiO2 nanofluid and investigate the effect of surfactant addition during the bead-milling process since the effect of different types of surfactant in the bead mill remains unclear and varied. The sol-gel method was used to synthesize SiO2 particles from waterglass. The preparation of SiO2 nanofluid began with screening surfactants to determine the optimum surfactant concentration. Then, the SiO2 nanofluid was prepared by using a bead mill with the addition of the surfactant. The Zeta potential analysis and particle size analyzer (PSA) were used to visualize the dispersion stability of all the prepared nanofluid samples. The results showed that adding 0.1 weight percent of PEG 6000 as a nonionic surfactant increased the stability of the dispersion, producing an average particle distribution of 502.7 nm and a zeta potential of -48.9 mV. The average value of particle size can be reduced using bead mill down to 241.7 nm (aggregate size) with 39.8 nm primary particle resulting in -45 mV zeta potential.

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D Primastari, S., Y. Kusumastuti, M. Handayani und Rochmadi. „Functionalization of multi-walled carbon nanotube (MWCNT) with CTACe surfactant and polyethylene glycol as potential drug carrier“. IOP Conference Series: Earth and Environmental Science 963, Nr. 1 (01.01.2022): 012033. http://dx.doi.org/10.1088/1755-1315/963/1/012033.

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Abstract Multi-walled Carbon Nanotube (MWCNT) pure is easy to form aggregate, making it difficult to apply as a drug carrier since it can be toxic to the body. It can be overcome by functionalization using surfactants, like cetyltrimethyl ammonium trichloro-monobromo-cerate (CTACe) and polyethylene glycol (PEG). First, MWCNT was functionalized with CTACe surfactant, then further PEG 6000 was used with several MWCNT-CTACe ratios. The functionalization was conducted under ultrasonic treatment, then followed by filtration, washing, and drying. The functionalized MWCNT underwent dispersion tests using water and dimethyl sulfoxide (DMSO) as the solvents. A dispersion test with water solvent shows that the functionalized MWCNT still forms aggregates within a few minutes. Whereas, in DMSO solvent, the functionalized MWCNT can be stabilized for more than five days without forming aggregates. FTIR results show a new peak at 1105 cm−1 and an increased peak intensity around 3432 cm−1, corresponding to C-N and hydrogen bonding of N-H vibration from the CTACe. The FTIR from PEG addition shows an increase in the wavenumbers around 3432,87 cm−1, indicating the strength of O-H/N-H intermolecular hydrogen interactions of O-H PEG with N-H surfactant ether bonds.

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Costa, Telma, Diego de Azevedo, Beverly Stewart, Matti Knaapila, Artur J. M. Valente, Mario Kraft, Ullrich Scherf und Hugh D. Burrows. „Interactions of a zwitterionic thiophene-based conjugated polymer with surfactants“. Polymer Chemistry 6, Nr. 46 (2015): 8036–46. http://dx.doi.org/10.1039/c5py01210d.

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Structural organization and photoluminescence properties of zwitterionic conjugated polymer–surfactant assemblies depend on specific and non-specific polymer–surfactant interactions within the aggregate.

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Russo, Thomas A., Lori A. Bartholomew, Bruce A. Davidson, Jadwiga D. Helinski, Ulrike B. Carlino, Paul R. Knight, Michael F. Beers, Elena N. Atochina, Robert H. Notter und Bruce A. Holm. „Total extracellular surfactant is increased but abnormal in a rat model of gram-negative bacterial pneumonia“. American Journal of Physiology-Lung Cellular and Molecular Physiology 283, Nr. 3 (01.09.2002): L655—L663. http://dx.doi.org/10.1152/ajplung.00071.2002.

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An in vivo rat model was used to evaluate the effects of Escherichia coli pneumonia on lung function and surfactant in bronchoalveolar lavage (BAL). Total extracellular surfactant was increased in infected rats compared with controls. BAL phospholipid content in infected rats correlated with the severity of alveolar-capillary leak as reflected in lavage protein levels ( R2= 0.908, P < 0.0001). Western blotting showed that levels of surfactant protein (SP)-A and SP-D in BAL were significantly increased in both large and small aggregate fractions at 2 and 6 h postinstillation of E. coli. SP-B was also increased at these times in the large aggregate fraction of BAL, whereas SP-C levels were increased at 2 h and decreased at 6 h relative to controls. The small-to-large (S/L) aggregate ratio (a marker inversely proportional to surfactant function) was increased in infected rats with >50 mg total BAL protein. There was a significant correlation ( R2= 0.885, P < 0.0001) between increasing S/L ratio in BAL and pulmonary damage assessed by total protein. Pulmonary volumes, compliance, and oxygen exchange were significantly decreased in infected rats with >50 mg of total BAL protein, consistent with surfactant dysfunction. In vitro surface cycling studies with calf lung surfactant extract suggested that bacterially derived factors may have contributed in part to the surfactant alterations seen in vivo.

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Harada, Takunori, Hiroshi Moriyama, Hiromi Takahashi, Kazuo Umemura, Haruo Yokota, Ryo Kawakami und Kenji Mishima. „Spectroscopic Characterization of Supramolecular Chiral Porphyrin Homoassociates at the Air–Water Interface“. Applied Spectroscopy 68, Nr. 11 (November 2014): 1235–40. http://dx.doi.org/10.1366/13-07432.

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The water-soluble 4-sulfonatophenyl meso-substituted porphyrin (TPPS) dye exhibits a transformation to a chiral self-aggregate from the non-aggregated species (diprotonated H4TPPS2–) at low concentration (no more than 1 × 10−5 M). Immobilization of supramolecular chiral porphyrin homoassociates was mediated by the electrostatic interaction between the anionic TPPS molecule and cationic surfactant monolayer at the air–water interface. With the immobilization, a reversible transformation from monomeric TPPS to J-aggregate ( M→J) could be changed into an irreversible ( M→J), which is desirable for stabilization of aggregation structure for a long period. The novel finding was achieved using a fine-tuned specialized solid-state circular dichroism (CD) spectrophotometer and derived analytical procedure to obtain artifact-free CD signals. To our knowledge, this is the first report achieving the chiral control of a homoassociate induced by a chiral surfactant at the air–water interface, indicating that the handedness of the formed homoassociate could be determined.

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Lehrsch, G. A., R. E. Sojka und A. C. Koehn. „Surfactant effects on soil aggregate tensile strength“. Geoderma 189-190 (November 2012): 199–206. http://dx.doi.org/10.1016/j.geoderma.2012.06.015.

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Ridder, Kristin B., Craig J. Davies-Cutting und Ian W. Kellaway. „Surfactant solubility and aggregate orientation in hydrofluoroalkanes“. International Journal of Pharmaceutics 295, Nr. 1-2 (Mai 2005): 57–65. http://dx.doi.org/10.1016/j.ijpharm.2005.01.027.

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Davidson, Bruce A., Paul R. Knight, Zhengdong Wang, Patricia R. Chess, Bruce A. Holm, Thomas A. Russo, Alan Hutson und Robert H. Notter. „Surfactant alterations in acute inflammatory lung injury from aspiration of acid and gastric particulates“. American Journal of Physiology-Lung Cellular and Molecular Physiology 288, Nr. 4 (April 2005): L699—L708. http://dx.doi.org/10.1152/ajplung.00229.2004.

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This study examines surfactant dysfunction in rats with inflammatory lung injury from intratracheal instillation of hydrochloric acid (ACID, pH 1.25), small nonacidified gastric particles (SNAP), or combined acid and small gastric particles (CASP). Rats given CASP had the most severe lung injury at 6, 24, and 48 h based on decreases in arterial oxygenation and increases in erythrocytes, total leukocytes, neutrophils, total protein, and albumin in bronchoalveolar lavage (BAL). The content of large surfactant aggregates in BAL was reduced in all forms of aspiration injury, but decreases were greatest in rats given CASP. Large aggregates from aspiration-injured rats also had decreased levels of phosphatidylcholine (PC) and increased levels of lyso-PC and total protein compared with saline controls (abnormalities for CASP were greater than for SNAP or ACID alone). The surface tension-lowering ability of large surfactant aggregates on a bubble surfactometer was impaired in rats with aspiration injury at 6, 24, and 48 h, with the largest activity reductions found in animals given CASP. There were strong statistical correlations between surfactant dysfunction (increased minimum surface tension and reduced large aggregate content) and the severity of lung injury based on arterial oxygenation and levels of albumin, protein, and erythrocytes in BAL ( P < 0.0001). Surfactant dysfunction also correlated strongly with reduced lung volumes during inflation and deflation ( P = 0.0004–0.005). These results indicate that surfactant abnormalities are functionally important in gastric aspiration lung injury and contribute significantly to the increased severity of injury found in CASP compared with ACID or SNAP alone.

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Zhong, Hua, Lei Yang, Guangming Zeng, Mark L. Brusseau, Yake Wang, Yang Li, Zhifeng Liu, Xingzhong Yuan und Fei Tan. „Aggregate-based sub-CMC solubilization of hexadecane by surfactants“. RSC Advances 5, Nr. 95 (2015): 78142–49. http://dx.doi.org/10.1039/c5ra12388g.

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SDBS or Triton X-100 at sub-CMC concentrations enhances hexadecane solubilization due to the aggregate formation mechanism. The sub-CMC aggregate size decreases with increasing surface excess of the surfactant.

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Puligandla, Pramod S., Tara Gill, Lynda A. McCaig, Li-Juan Yao, Ruud A. W. Veldhuizen, Fred Possmayer und James F. Lewis. „Alveolar environment influences the metabolic and biophysical properties of exogenous surfactants“. Journal of Applied Physiology 88, Nr. 3 (01.03.2000): 1061–71. http://dx.doi.org/10.1152/jappl.2000.88.3.1061.

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Several factors have been shown to influence the efficacy of exogenous surfactant therapy in the acute respiratory distress syndrome. We investigated the effects of four different alveolar environments (control, saline-lavaged, N-nitroso- N-methylurethane, and hydrochloric acid) on the metabolic and functional properties of two exogenous surfactant preparations: bovine lipid extract surfactant and recombinant surfactant-associated protein (SP) C drug product (rSPC) administered to each of these groups. The main difference between these preparations was the lack of SP-B in the rSPC. Our results demonstrated differences in the large aggregate pool sizes recovered from each of the experimental groups. We also observed differences in SP-A content, surface area cycling characteristics, and biophysical activities of these large aggregate forms after the administration of the two exogenous surfactant preparations. We conclude that the alveolar environment plays a critical role, influencing the overall efficacy of exogenous surfactant therapy. Thus further preclinical studies are warranted to investigate the specific factors within the alveolar environment that lead to the differences observed in this study.

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Oliveira, Isabel S., Sandra G. Silva, Maria Luísa do Vale und Eduardo F. Marques. „Model Catanionic Vesicles from Biomimetic Serine-Based Surfactants: Effect of the Combination of Chain Lengths on Vesicle Properties and Vesicle-to-Micelle Transition“. Membranes 13, Nr. 2 (01.02.2023): 178. http://dx.doi.org/10.3390/membranes13020178.

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Mixtures of cationic and anionic surfactants often originate bilayer structures, such as vesicles and lamellar liquid crystals, that can be explored as model membranes for fundamental studies or as drug and gene nanocarriers. Here, we investigated the aggregation properties of two catanionic mixtures containing biomimetic surfactants derived from serine. The mixtures are designated as 12Ser/8-8Ser and 14Ser/10-10Ser, where mSer is a cationic, single-chained surfactant and n-nSer is an anionic, double-chained one (m and n being the C atoms in the alkyl chains). Our goal was to investigate the effects of total chain length and chain length asymmetry of the catanionic pair on the formation of catanionic vesicles, the vesicle properties and the vesicle/micelle transitions. Ocular observations, surface tension measurements, video-enhanced light microscopy, cryogenic scanning electron microscopy, dynamic and electrophoretic light scattering were used to monitor the self-assembly process and the aggregate properties. Catanionic vesicles were indeed found in both systems for molar fractions of cationic surfactant ≥0.40, always possessing positive zeta potentials (ζ = +35–50 mV), even for equimolar sample compositions. Furthermore, the 14Ser/10-10Ser vesicles were only found as single aggregates (i.e., without coexisting micelles) in a very narrow compositional range and as a bimodal population (average diameters of 80 and 300 nm). In contrast, the 12Ser/8-8Ser vesicles were found for a wider sample compositional range and as unimodal or bimodal populations, depending on the mixing ratio. The aggregate size, pH and zeta potential of the mixtures were further investigated. The unimodal 12Ser/8-8Ser vesicles (<DH> ≈ 250 nm, pH ≈ 7–8, ζ ≈ +32 mV and a cationic/anionic molar ratio of ≈2:1) are particularly promising for application as drug/gene nanocarriers. Both chain length asymmetry and total length play a key role in the aggregation features of the two systems. Molecular insights are provided by the main findings.

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Maitra, Gayatri, Kevin Inchley, Richard J. Novick, Ruud A. W. Veldhuizen, James F. Lewis und Fred Possmayer. „Acute lung injury and lung transplantation influence in vitro subtype conversion of pulmonary surfactant“. American Journal of Physiology-Lung Cellular and Molecular Physiology 282, Nr. 1 (01.01.2002): L67—L74. http://dx.doi.org/10.1152/ajplung.2002.282.1.l67.

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The effects of surfactant treatment on surfactant subtype conversion after lung injury were examined. Dogs were subjected to hyperventilation for 8 h with or without surfactant treatment. Lungs were stored for 17 h, and the right lung was transplanted and reperfused for 6 h. Conversion of large aggregate (LA) surfactant to small aggregates was investigated using in vitro surface area cycling. LA from transplanted lungs (Transplant-LA) from the nontreated group converted more rapidly than Transplant-LA from the treated group. Transplant-LA from both groups converted more rapidly than LA from normal lungs. Calculations based on [3H]dipalmitoylphosphatidylcholine in the administered surfactant [bovine lipid extract surfactant (BLES)] showed that the endogenous component of Transplant-LA converted more rapidly than the exogenous component. This indicates exogenous BLES did not equilibrate completely with endogenous surfactant. LA from hyperventilated, stored donor right lungs and from the recipients' native lungs from the nontreated group converted more rapidly than corresponding LA in the BLES-treated group. Similar relative conversions were observed with exogenous components from all lungs. Relative conversion of endogenous component from Transplant-LA was more rapid than that from LA from donor's stored right lung or from the recipient's native right lung. Low levels of phenylmethylsulfonyl fluoride inhibited conversion of Transplant-LA to a greater extent than normal LA. LA from all experimental groups had similar protein levels. These studies show acute lung injury, transplant, ischemia-reperfusion, and surfactant treatment have major effects on surfactant subtype integrity.

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Cid, Antonio, Oscar Moldes, Juan Mejuto und Jesus Simal-Gandara. „Interaction of Caffeic Acid with SDS Micellar Aggregates“. Molecules 24, Nr. 7 (27.03.2019): 1204. http://dx.doi.org/10.3390/molecules24071204.

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Micellar systems consisting of a surfactant and an additive such as an organic salt or an acid usually self-organize as a series of worm-like micelles that ultimately form a micellar network. The nature of the additive influences micellar structure and properties such as aggregate lifetime. For ionic surfactants such as sodium dodecyl sulfate (SDS), CMC decreases with increasing temperature to a minimum in the low-temperature region beyond which it exhibits the opposite trend. The presence of additives in a surfactant micellar system also modifies monomer interactions in aggregates, thereby altering CMC and conductance. Because the standard deviation of β was always lower than 10%, its slight decrease with increasing temperature was not significant. However, the absolute value of Gibbs free enthalpy, a thermodynamic potential that can be used to calculate the maximum of reversible work, increased with increasing temperature and caffeic acid concentration. Micellization in the presence of caffeic acid was an endothermic process, which was entropically controlled. The enthalpy and enthropy positive values resulted from melting of “icebergs” or “flickering clusters” around the surfactant, leading to increased packing of hydrocarbon chains within the micellar core in a non-random manner. This can be possibly explained by caffeic acid governing the 3D matrix structure of water around the micellar aggregates. The fact that both enthalpy and entropy were positive testifies to the importance of hydrophobic interactions as a major driving force for micellization. Micellar systems allow the service life of some products to be extended without the need to increase the amounts of post-harvest storage preservatives used. If a surfactant is not an allowed ingredient or food additive, carefully washing it off before the product is consumed can avoid any associated risks. In this work, we examined the influence of temperature and SDS concentration on the properties of SDS–caffeic acid micellar systems. Micellar properties can be modified with various additives to develop new uses for micelles. This allows smaller amounts of additives to be used without detracting from their benefits.

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Zhang, Yongmin, Weiwei Kong, Cheng Wang, Pengyun An, Yun Fang, Yujun Feng, Zhirong Qin und Xuefeng Liu. „Switching wormlike micelles of selenium-containing surfactant using redox reaction“. Soft Matter 11, Nr. 38 (2015): 7469–73. http://dx.doi.org/10.1039/c5sm01515d.

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Wormlike micelles based on a selenium-containing surfactant and a commercially anionic surfactant reversibly respond to H₂O₂ and vitamin C, and show circulatory gel/sol transition, reflecting changes in aggregate morphology from entangled worms to vesicles.

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McGowan, F. X., M. lkegami, E. K. Motoyama, G. Kurland, P. J. Davis, R. D. Siewers und S. Firestone. „ALTERED SURFACTANT AGGREGATE FRACTIONS FOLLOWING PEDIATRIC CARDIOPULMONARY BYPASS“. Anesthesiology 77, Supplement (September 1992): A1138. http://dx.doi.org/10.1097/00000542-199209001-01138.

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Sen, Sobhan, Dipankar Sukul, Partha Dutta und Kankan Bhattacharyya. „Photoisomerization of merocyanine 540 in polymer-surfactant aggregate“. Journal of Chemical Sciences 114, Nr. 1 (Februar 2002): 83–91. http://dx.doi.org/10.1007/bf02709984.

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Okuzaki, H., und Y. Osada. „Ordered-Aggregate Formation by Surfactant-Charged Gel Interaction“. Macromolecules 28, Nr. 1 (Januar 1995): 380–82. http://dx.doi.org/10.1021/ma00105a054.

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Pérez, Lourdes, Aurora Pinazo, M. C. Morán und Ramon Pons. „Aggregation Behavior, Antibacterial Activity and Biocompatibility of Catanionic Assemblies Based on Amino Acid-Derived Surfactants“. International Journal of Molecular Sciences 21, Nr. 23 (24.11.2020): 8912. http://dx.doi.org/10.3390/ijms21238912.

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The surface activity, aggregates morphology, size and charge characteristics of binary catanionic mixtures containing a cationic amino acid-derived surfactant N(π), N(τ)-bis(methyl)-L-Histidine tetradecyl amide (DMHNHC14) and an anionic surfactant (the lysine-based surfactant Nα-lauroyl-Nεacetyl lysine (C12C3L) or sodium myristate) were investigated for the first time. The cationic surfactant has an acid proton which shows a strong pKa shift irrespective of aggregation. The resulting catanionic mixtures exhibited high surface activity and low critical aggregation concentration as compared with the pure constituents. Catanionic vesicles based on DMHNHC14/sodium myristate showed a monodisperse population of medium-size aggregates and good storage stability. According to Small-Angle X-Ray Scattering (SAXS), the characteristics of the bilayers did not depend strongly on the system composition for the positively charged vesicles. Negatively charged vesicles (cationic surfactant:myristate ratio below 1:2) had similar bilayer composition but tended to aggregate. The DMHNHC14-rich vesicles exhibited good antibacterial activity against Gram-positive bacteria and their bactericidal effectivity declined with the decrease of the cationic surfactant content in the mixtures. The hemolytic activity and cytotoxicity of these catanionic formulations against non-tumoral (3T3, HaCaT) and tumoral (HeLa, A431) cell lines also improved by increasing the ratio of cationic surfactant in the mixture. These results indicate that the biological activity of these systems is mainly governed by the cationic charge density, which can be modulated by changing the cationic/anionic surfactant ratio in the mixtures. Remarkably, the incorporation of cholesterol in those catanionic vesicles reduces their cytotoxicity and increases the safety of future biomedical applications of these systems.

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Dharaiya, Nilesh, Urja Patel, Debes Ray, Vinod K. Aswal, Nandhibatla V. Sastry und Pratap Bahadur. „Different pH triggered aggregate morphologies in sodium oleate–cationic surfactants mixed systems“. New Journal of Chemistry 41, Nr. 17 (2017): 9142–51. http://dx.doi.org/10.1039/c6nj03871a.

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Pashirova, Tatiana N., Andrei V. Bogdanov, Lenar I. Musin, Julia K. Voronina, Irek R. Nizameev, Marsil K. Kadirov, Vladimir F. Mironov, Lucia Ya Zakharova, Shamil K. Latypov und Oleg G. Sinyashin. „Nanoscale isoindigo-carriers: self-assembly and tunable properties“. Beilstein Journal of Nanotechnology 8 (01.02.2017): 313–24. http://dx.doi.org/10.3762/bjnano.8.34.

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Over the last decade isoindigo derivatives have attracted much attention due to their high potential in pharmacy and in the chemistry of materials. In addition, isoindigo derivatives can be modified to form supramolecular structures with tunable morphologies for the use in drug delivery. Amphiphilic long-chain dialkylated isoindigos have the ability to form stable solid nanoparticles via a simple nanoprecipitation technique. Their self-assembly was investigated using tensiometry, dynamic light scattering, spectrophotometry, and fluorometry. The critical association concentrations and aggregate sizes were measured. The hydrophilic–lipophilic balance of alkylated isoindigo derivatives strongly influences aggregate morphology. In the case of short-chain dialkylated isoindigo derivatives, supramolecular polymers of 200 to 700 nm were formed. For long-chain dialkylated isoindigo derivatives, micellar aggregates of 100 to 200 nm were observed. Using micellar surfactant water-soluble forms of monosubstituted 1-hexadecylisoindigo as well as 1,1′-dimethylisoindigo were prepared for the first time. The formation of mixed micellar structures of different types in micellar anionic surfactant solutions (sodium dodecyl sulfate) was determined. These findings are of practical importance and are of potential interest for the design of drug delivery systems and new nanomaterials.

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Russo, Thomas A., Zhengdong Wang, Bruce A. Davidson, Stacy A. Genagon, Janet M. Beanan, Ruth Olson, Bruce A. Holm, Paul R. Knight, Patricia R. Chess und Robert H. Notter. „Surfactant dysfunction and lung injury due to theE. colivirulence factor hemolysin in a rat pneumonia model“. American Journal of Physiology-Lung Cellular and Molecular Physiology 292, Nr. 3 (März 2007): L632—L643. http://dx.doi.org/10.1152/ajplung.00326.2006.

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This study tests the hypothesis that the virulence factor hemolysin (Hly) expressed by extraintestinal pathogenic Escherichia coli contributes to surfactant dysfunction and lung injury in a rat model of gram-negative pneumonia. Rats were instilled intratracheally with CP9 (wild type, Hly-positive), CP9 hlyA (Hly-minus), CP9 /pEK50 (supraphysiological Hly), or purified LPS. At 6 h postinfection, rats given CP9 had a decreased percentage content of large surfactant aggregates in cell-free bronchoalveolar lavage (BAL), decreased large aggregate surface activity, decreased PaO2/FiO2ratio, increased BAL albumin/protein levels, and increased histological evidence of lung injury compared with rats given CP9 hlyA or LPS. In addition, rats given CP9/ pEK50 or CP9 had decreased large aggregate surface activity, decreased PaO2/FiO2ratios, and increased BAL albumin/protein levels at 2 h postinfection compared with rats given CP9 hlyA. The severity of permeability lung injury based on albumin/protein levels in BAL at 2 h was ordered as CP9 /pEK50 > CP9 > CP9 hlyA > normal saline controls. Total lung titers of bacteria were increased at 6 h in rats given CP9 vs. CP9 hlyA, but bacterial titers were not significantly different at 2 h, indicating that increased surfactant dysfunction and lung injury were associated with Hly as opposed to bacterial numbers per se. Further studies in vitro showed that CP9 could directly lyse transformed pulmonary epithelial cells (H441 cells) but that indirect lysis of H441 cells secondary to Hly-induced neutrophil lysis did not occur. Together, these data demonstrate that Hly is an important direct mediator of surfactant dysfunction and lung injury in gram-negative pneumonia.

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Charde, Rashmi P., Brian van Devener und Michael M. Nigra. „Surfactant- and Ligand-Free Synthesis of Platinum Nanoparticles in Aqueous Solution for Catalytic Applications“. Catalysts 13, Nr. 2 (21.01.2023): 246. http://dx.doi.org/10.3390/catal13020246.

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The synthesis of surfactant-free and organic ligand-free metallic nanoparticles in solution remains challenging due to the nanoparticles’ tendency to aggregate. Surfactant- and ligand-free nanoparticles are particularly desirable in catalytic applications as surfactants, and ligands can block access to the nanoparticles’ surfaces. In this contribution, platinum nanoparticles are synthesized in aqueous solution without surfactants or bound organic ligands. Pt is reduced by sodium borohydride, and the borohydride has a dual role of reducing agent and weakly interacting stabilizer. The 5.3 nm Pt nanoparticles are characterized using UV-visible spectroscopy and transmission electron microscopy. The Pt nanoparticles are then applied as catalysts in two different reactions: the redox reaction of hexacyanoferrate(III) and thiosulfate ions, and H2O2 decomposition. Catalytic activity is observed for both reactions, and the Pt nanoparticles show up to an order of magnitude greater activity over the most active catalysts reported in the literature for hexacyanoferrate(III)/thiosulfate redox reactions. It is hypothesized that this enhanced catalytic activity is due to the increased electron density that the surrounding borohydride ions give to the Pt nanoparticle surface, as well as the absence of surfactants or organic ligands blocking surface sites.

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Haritonovs, Viktors. „Evaluation of polyaminoamide as a surfactant additive in hot mix asphalt“. Baltic Journal of Road and Bridge Engineering 10, Nr. 2 (25.06.2015): 112–17. http://dx.doi.org/10.3846/bjrbe.2015.14.

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The phenomenon of breaking the bond between the aggregates and the bitumen is known as stripping. Strip-ping of asphalt films from the surface of aggregate particles results in premature failure of asphalt pavement. This causes weakening of pavement resistance to rutting and fatigue. Furthermore, moisture damage increases the susceptibility of pavement to reveling, a distress that causes the loss of skid resistance on surface of the road and deterioration of pavement. Surfactant additive or adhesive agent is a surface-active agent that changes (lowers) the surface tension of rock materials. Introduction of surfactant additive results in increased strength of adhesive bond between bitumen and the rock materials surface preventing stripping throughout the service life of the asphalt concrete. Polyaminoamide is an organic water soluble compound that allows waterproofing mineral aggregate surfaces and acts as a bonding agent to bitumen. The objective of this research is to study the effect of polyaminoamide based and pholiphosphoric acid based liquid additives on stripping, moisture susceptibility, rutting and fatigue performance of asphalt concrete. In this paper, boiling water test was used to determine the percentage of stripped aggregates after boiling. The moisture susceptibility of asphalt mixtures was investigated by means of testing the retained indirect tensile strength after water immersion using Marshal stability test method. Wheel tracking test was also conducted on asphalt slabs prepared in the laboratory to determine rut resistance. Asphalt concrete with commonly used mineral filler was chosen as a control mixture. It was found that the adhesion additive not only improves stripping resistance, but also slightly improves asphalt rut resistance.

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Allen, Victoria, Margaret Oulton, Dora Stinson, Josee MacDonald und Alexander Allen. „Alveolar metabolism of natural vs. synthetic surfactants in preterm newborn rabbits“. Journal of Applied Physiology 90, Nr. 1 (01.01.2001): 198–204. http://dx.doi.org/10.1152/jappl.2001.90.1.198.

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We compared the recoveries of four surfactant preparations: two natural [term fetal rabbit surfactant (FRS) and adult rabbit surfactant (ARS)] and two commercially available preparations [apoprotein-based Survanta (S) and synthetic Exosurf (E)] from 27-day gestation rabbit pups treated at birth and ventilated up to 120 min. At 5, 60, and 120 min, we measured the recovery of the heavy-aggregate, metabolically active form (H) and the light-aggregate, nonsurface active metabolic breakdown form (L) of alveolar surfactant and determined the phospholipid content and composition of the intracellularly stored lamellar body (LB) pool. Pups treated with FRS had <15% loss of H by 2 h. ARS-treated pups had a >50% loss of H by 1 h, and E- and S-treated pups had ∼50% loss by 5 min, with a slower rate of continuing loss of up to 80% by 2 h. The major losses of H phospholipid were not explained by the L-form recovery. LB phospholipid significantly increased only in the E-treated pups and only at 2 h. FRS provides a biologically active form (H) of surfactant that appeared to remain in the airway for a significantly longer time than the other surfactant preparations. The unique properties of FRS merit further study.

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Chaban, Vitaly V., Andre Arruda und Eudes Eterno Fileti. „Polypeptide A9K at nanoscale carbon: a simulation study“. Physical Chemistry Chemical Physics 17, Nr. 39 (2015): 26386–93. http://dx.doi.org/10.1039/c5cp04565g.

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Barth, Brian, und Thomas A. Zawodzinski. „Exploring Surfactant Electrolyte-Porous Electrode Interactions“. ECS Meeting Abstracts MA2023-01, Nr. 24 (28.08.2023): 1593. http://dx.doi.org/10.1149/ma2023-01241593mtgabs.

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Microemulsions are an alternative to aqueous organic electrolytes for redox flow batteries (RFB) that can be modified without synthesis. Water, oil, and emulsifiers, when combined using optimized chemistries and compositions, produce stable mixtures with aggregate structures (microemulsions). Design limitations imposed by the interdependency of redox solubility and electrolyte conductivity are circumvented by solubilizing redox active molecules in the oil phase and supporting ions in the aqueous phase. While macroscopically homogeneous, microemulsions are biphasic at the nanometer scale, effectively decoupling solubility from conductivity. Recently, the first microemulsion RFB was demonstrated using ferrocene solubilized in an anionic surfactant system. Polarization curve analysis revealed performance limitations seemingly arising from electrolyte interactions with the cell components including porous electrodes. Further optimization requires a deeper understanding of microemulsion-porous electrode interactions. Due to the complexity of microemulsion electrochemistry, a first step towards understanding these interactions is made by investigating the relationship between surfactants and porous electrodes. Vanadium redox flow battery (VRFB) electrolytes with surfactant additives are used as a model system to explore fundamental interactions, in situ, between a surfactant-containing electrolyte and a porous electrode. Transport and kinetics are evaluated as a function of electrode, electrolyte, and surfactant properties. Redox species transport is quantified through mass transfer coefficients, using a generalization of an existing porous electrode model fit to experimental polarization curve data. Electrochemical impedance spectroscopy, interpreted using existing kinetic models, is also employed to gain insight into the effects of surfactant on electron transfer rates.

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McKerrow, Andrew J., Erwin Buncel und Peter M. Kazmaier. „Aggregation of squaraine dyes: Structure–property relationships and solvent effects“. Canadian Journal of Chemistry 73, Nr. 10 (01.10.1995): 1605–15. http://dx.doi.org/10.1139/v95-200.

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In characterizing the UV–visible absorption properties of a series of seven anilino class squaraine dyes in dimethyl sulfoxide (DMSO) – water mixtures, spectral features characteristic of aggregation were observed. These included hypsochromic and hypochromic shifts of the absorption maximum, relative to the nonassociated state of these dyes. Previously aggregation of this class of squaraine dyes had only been reported in studies of Langmuir–Blodgett (LB) films prepared with squaraine dyes. In the present study two distinctly different and novel solution dye aggregates, designated as type A and type B, were identified on the basis of their characteristic absorption properties. The type A aggregate was characterized by an absorption maximum that was hypsochromically and hypochromically shifted, in comparison with that of the nonassociated dyes, and had a secondary absorption occurring at approximately the same wavelength at which nonassociated squaraine dyes absorb. These spectral features are believed to be the result of a "face-to-face" alignment of molecules in the aggregate. The type B aggregate featured a broad absorption typically from 525 to 700 nm. Based on similarities between the spectral features of type B aggregates and LB films of surfactant squaraines, the alignment of molecules in the solution aggregate was believed to be such that the electron-deficient squarylium moieties interacted with the electron-rich dialkylamino phenyl moieties. Certain squaraine dyes that were investigated as part of this study were found to form both type A and type B aggregates, depending upon the composition of the DMSO–water medium. Typically, the type A aggregate formed preferentially in media of intermediate DMSO content (50–70% DMSO) and the type B aggregate in more water-rich media (<20% DMSO). In the intervening region it was possible to monitor spectroscopically a dynamic conversion from the type B aggregate to the type A aggregate. An examination of structure–property relationships indicated that dyes with less hydrophobic N-alkyl substituents formed only type A aggregates. Squaraine dyes with more hydrophobic N-alkyl substituents were found to form type B aggregates in water and type A aggregates in some DMSO–water mixtures. A model of squaraine aggregation was proposed in which the type A squaraine aggregate was "thermodynamically" preferred while the type B aggregate was "kinetically" preferred. The stability of the type B aggregate was proposed to be enhanced by increasing hydrophobicity of the N-alkyl substituents and decreased by increasing amounts of DMSO in the solvent system. Keywords: squaraine dyes, aggregation, crystallochromy, solvent effects.

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Chithralekha, N., und A. Panneerselvam. „Physico-Chemical Analysis on Some Polymers in Aqueous Surfactant Solution at Different Temperatures: Acoustical, UV and FTIR Studies“. Asian Journal of Chemistry 31, Nr. 3 (2019): 674–78. http://dx.doi.org/10.14233/ajchem.2019.21771.

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The ultrasonic velocity, density and viscosity in mixtures of sorbitan sesquioleate and poly(vinyl pyrrolidone) (PVP), poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG) in different concentration ranges are measured at different temperatures (303, 313 and 323 K). From the experimental data, other related acoustical parameters such as adiabatic compressibility (β), intermolecular free length (Lf), internal pressure (πi), Rao’s constant (Ra), relaxation time (τ), acoustical impedance (Za), absorption coefficient (α/f2), free volume (Vf), cohesive energy (CE) and solvation number (Sn) have been evaluated. In aqueous solutions, surfactant molecule starts to aggregate and form micelle in concentration called as critical micelle concentration (CMC). It is one of the most important physical parameters of the surfactants. These results were interpreted in terms of surfactantpolymer complex reactions. The combinations of surfactant with polymers improve the desired properties of the product and the formation of complex was confirmed by UV and FTIR studies.

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Torres-Luna, Cesar, Abdollah Koolivand, Xin Fan, Niti R. Agrawal, Naiping Hu, Yuli Zhu, Roman Domszy, Robert M. Briber, Nam Sun Wang und Arthur Yang. „Formation of Drug-Participating Catanionic Aggregates for Extended Delivery of Non-Steroidal Anti-Inflammatory Drugs from Contact Lenses“. Biomolecules 9, Nr. 10 (10.10.2019): 593. http://dx.doi.org/10.3390/biom9100593.

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This paper focuses on extending drug release duration from contact lenses by incorporating catanionic aggregates. The aggregates consist of a long-chain cationic surfactant, i.e., cetalkonium chloride (CKC), and an oppositely charged anti-inflammatory amphiphilic drug. We studied three non-steroidal anti-inflammatory (NSAID) drugs with different octanol–water partition coefficients; diclofenac sodium (DFNa), flurbiprofen sodium (FBNa), and naproxen sodium (NPNa). Confirmation of catanionic aggregate formation in solution was determined by steady and dynamic shear rheology measurements. We observed the increased viscosity, shear thinning, and viscoelastic behavior characteristic of wormlike micelles; the rheological data are reasonably well described using a Maxwellian fluid model with a single relaxation time. In vitro release experiments demonstrated that the extension in the drug release time is dependent on the ability of a drug to form viscoelastic catanionic aggregates. Such aggregates retard the diffusive transport of drug molecules from the contact lenses. Our study revealed that the release kinetics depends on the CKC concentration and the alkyl chain length of the cationic surfactant. We demonstrated that more hydrophobic drugs such as diclofenac sodium show a more extended release than less hydrophobic drugs such as naproxen sodium.

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Wang, Ruijuan, Ying Qin, Shuo Yang, Dong Wang und Zhigang Yin. „Study on Interaction of Carboxylic Acid Gemini Surfactant with Cocamidopropyl Betaine in Aqueous Solution“. Tenside Surfactants Detergents 58, Nr. 3 (01.05.2021): 204–10. http://dx.doi.org/10.1515/tsd-2020-2284.

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Abstract The interaction of carboxylic acid gemini surfactant 4,8-didodecyl-3,9-dioxo-6-hydroxy-4,8-diaza-1,11-undecanedicarboxylic acid (CGS12) with amphoteric surfactant cocamidopropyl betaine (CAPB) at 258C and pH 7.0 has been investigated using pH titration, surface tension, dynamic light scattering (DLS) and cryogenic transmission electron microscopy (Cryo-TEM) measurements. The pH titration results show that CGS12 exhibits anionic surfactant properties and CAPB exists as a zwitterionic form at pH 7.0. The surface tension results show that the critical micelle concentration (CMC) values of the CAPB/CGS12 mixture are low, and basically exhibit a decreasing trend with decreasing molar ratio of CAPB (XCAPB). The variation of the CMC of the mixture reveals that the mixing is close to ideal. The DLS results indicate that the CAPB/ CGS12 mixture mainly forms the larger aggregates with the hydrate radii approximately 70-145 nm at various XCAPB. The Cryo-TEM images further demonstrate the CAPB/CGS12 mixtures mainly form vesicles. The results indicate that the aggregate size and microstructure of the mixture change little with the variation of XCAPB.

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