Search results for "Surfactant"
showing 10 items of 397 documents
Calorimetric and Volumetric Investigations of the Effect of the Hydrophobicity of the Surfactant on the Binding between (Ethylene oxide)13-(propylene…
2004
The enthalpy and the volume of transfer (DeltaY(t)) of the unassociated (ethylene oxide)(13)-(propylene oxide)(30)-(ethylene oxide)(13) (L64) from water to the aqueous sodium alkanoate solutions as functions of the surfactant concentrations (m(S)) were determined at 298 K. The surfactants studied are sodium hexanoate, sodium heptanoate, sodium octanoate, sodium undecanoate, and sodium dodecanoate. As a general feature, for the short alkyl chain surfactants, DeltaY(t) describes an S-shaped curve in the range of m(S) analyzed whereas for the more hydrophobic surfactants the DeltaY(t) vs m(S) trends exhibit maxima which appear at ms values very close to the critical micellar concentration in w…
The comparative spreading behavior of enantiomeric and racemic tyrosine amphiphiles
1985
Several derivatives of tyrosine or its methyl ester have been synthesized in which the para hydroxyl group on the aromatic side chain has been converted to a long chain alkyl ether or urethane. The surface behavior of these compounds is discussed. Enantiomeric discrimination, the ability of a chiral molecule to distinguish between mirror-image stereoisomers, has been investigated for the urethane derivates by comparing the surface pressure-area isotherms of the enantiomer with that of the racemic compound. Enantiomeric discrimination was demonstrated for the methyl ester analog, but was not conclusively observed for the zwitterionic compounds. Possible structural requirements for enantiomer…
Polymeric nanoparticles of different sizes overcome the cell membrane barrier.
2012
Abstract Polymeric nanoparticles have tremendous potential either as carriers or markers in treatment for diseases or as diagnostics in biomedical applications. Finding the optimal conditions for effective intracellular delivery of the payload to the location of interest is still a big challenge. The particles have to overcome the barrier of the cell membrane. Here, we investigated the uptake in HeLa cells of fluorescent polystyrene particles with different size and surface charge. Particles stabilized with the nonionic surfactant Lutensol AT50® (132 nm, 180 nm, 242 nm, 816 nm, 846 nm diameter) were synthesized via dispersion polymerization. Cationic particles (120 nm, 208 nm, 267 nm, 603 n…
Thermodynamics of Surfactant, Block Copolymer and Their Mixtures in Water: The Role of the Isothermal Calorimetry
2009
The thermodynamics of conventional surfactants, block copolymers and their mixtures in water was described to the light of the enthalpy function. The two methodologies, i.e. the van't Hoff approach and the isothermal calorimetry, used to determine the enthalpy of micellization of pure surfactants and block copolymers were described. The van't Hoff method was critically discussed. The aqueous copolymer+surfactant mixtures were analyzed by means of the isothermal titration calorimetry and the enthalpy of transfer of the copolymer from the water to the aqueous surfactant solutions. Thermodynamic models were presented to show the procedure to extract straightforward molecular insights from the …
Olive mill wastewaters decontamination based on organo-nano-clay composites
2019
Abstract Green composites for environmental applications were successfully prepared by intercalation of the biosurfactant Quillaja saponin onto montmorillonite mineral clay on varying pH and surfactant/clay ratio. Equilibrium adsorption isotherms were constructed and the system was characterized by performing TGA and XRD analyses. The efficiency of the surfactant-modified clay in the removal of the organic content present in olive mill wastewaters (OMW) was evaluated by means of spectrophotometric measurements. The interest for this cogent issue comes from the consideration that, despite their high pollutant content, OMW can be considered as a potential resource of several organic compounds…
Compared effects of synthetic and natural bile acid surfactants on xenobiotic absorption I. Studies with polysorbate and taurocholate in rat colon
1991
Some expected differences between synthetic and natural bile acid surfactants relative to their influences on xenobiotic absorption are briefly outlined on the basis of literature data. Then, experimental work is presented which shows that these differences exist and that they can be even more relevant than suspected. Absorption tests were developed in rat colon in situ with polysorbate (synthetic) and sodium taurocholate (natural) surfactants, using a homologous series of phenylalkylcarboxylic acids as test compounds. At the critical micelle concentration (CMC), the two previously reported actions of synthetic surfactants on xenobiotic absorption (i.e. the increase in absorbing membrane po…
Absorption-partition relationships for true homologous series of xenobiotics as a possible approach to study mechanisms of surfactants in absorption.…
1992
Abstract This paper — the latest in this series of reports — deals with the effects of the anionic surfactant sodium lauryl sulfate on the colonic absorption of acidic xenobiotics (phenylalkylcarboxylic acids), as compared with those exerted by the nonionic polysorbate 80. The effects of these surfactants are qualitatively identical but quantitatively different. Thus, the increase in polarity of the colonic absorbant membrane is greater with lauryl sulfate, whereas micellar solubilization is much higher with polysorbate. As for the rest (i.e. the elimination of the stagnant aqueous diffusion layer as a limiting step for absorption), the two surfactants behave in a similar way. The biopharma…
Zn-Enhanced Asp-Rich Antimicrobial Peptides N-Terminal Coordination by Zn(II) and Cu(II), Which Distinguishes Cu(II) Binding to Different Peptides
2021
The antimicrobial activity of surfactant-associated anionic peptides (SAAPs), which are isolated from the ovine pulmonary surfactant and are selective against the ovine pathogen Mannheimia haemolytica, is strongly enhanced in the presence of Zn(II) ions. Both calorimetry and ITC measurements show that the unique Asp-only peptide SAAP3 (DDDDDDD) and its analogs SAAP2 (GDDDDDD) and SAAP6 (GADDDDD) have a similar micromolar affinity for Zn(II), which binds to the N-terminal amine and Asp carboxylates in a net entropically-driven process. All three peptides also bind Cu(II) with a net entropically-driven process but with higher affinity than they bind Zn(II) and coordination that involves the N…
Tuning the pore size from micro- to meso-porous in thermally stable aluminophosphates
1999
Thermally stable porous aluminophosphates (ICMUV-3) with P/Al molar ratios in the range 0.15 <= P/Al <= 0.75 and showing continuously adjustable pore sizes from 13 to 37 Å have been prepared through a surfactant-assisted procedure without changing the surfactant length and/or addition of organic expansors. Cabrera Medina, Saul, Saul.Cabrera@uv.es ; El Haskouri, Jamal, Jamal.Haskouri@uv.es ; Beltran Porter, Aurelio, Aurelio.Beltran@uv.es ; Beltran Porter, Daniel, Daniel.Beltran@uv.es ; Amoros del Toro, Pedro Jose, Pedro.Amoros@uv.es
Survey of neonatal respiratory care and surfactant administration in very preterm infants in the Italian neonatal network
2013
INTRODUCTION: Variation of respiratory care is described between centers around the world. The Italian Neonatal Network (INN), as a national group of the Vermont-Oxford Network (VON) allows to perform a wide analysis of respiratory care in very low birth weight infants. METHODS: We analyzed the dataset of infants enrolled in the INN in 2009 and 2010 and, for surfactant administration only, from 2006 to 2010 from 83 participating centers. All definitions are those of the (VON). A questionnaire analysis was also performed with a questionnaire on centers practices. RESULTS: We report data for 8297 infants. Data on ventilator practices and outcomes are outlined. Variation for both practices and…