Irina Portnaya

Technion - Israel Institute of Technology, Haifa, Haifa District, Israel

Are you Irina Portnaya?

Claim your profile

Publications (18)51.2 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Supramolecular chiral assemblies of R(-) and S(+) 2-butanol, in their neat form or when dissolved in their nonchiral isomer isobutanol, were evaluated by isothermal titration calorimetry (ITC) ensuing mixing. Dilution of 0.5 M solution of R(-) 2-butanol in isobutanol into the latter liberated heat of several calories per mole, which was approximately double than that obtained in parallel dilutions of S(+) 2-butanol in isobutanol. The ITC dilution profiles indicated an estimate of about 100 isobutanol solvent molecules surrounding each of the 2-butanol enantiomers, presumably arranged in chiral configurations, with different adopted order between the isomers. Mixings of neat R and S 2-butanol were followed by endothermic ITC profiles, indicating that, in racemic 2-butanol, both the supramolecular order and the intermolecular binding energies are lower than in each of the neat chiral isomers. The diversion from symmetrical ITC patterns in these mixings indicated again a subtle difference in molecular organization between the neat enantiomers. It should be noted that the presence of impurities, α-pinene and teterhydrofuran, at a level totaling 0.5%, did not influence the ITC heat flow profiles. The findings of this study demonstrate for the first time that chiral solutes in organic solvents are expected to acquire asymmetric solvent envelopes that may be different between the enantiomers, thus broadening this phenomenon beyond the previously demonstrated cases in aqueous solutions.
    Chirality 05/2012; 24(7):500-5. · 1.72 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: β-casein is an amphiphilic protein that self-organizes into well-defined core-shell micelles. We developed these micelles as efficient nanocarriers for oral drug delivery. Our model drug is celecoxib, an anti-inflammatory hydrophobic drug utilized for treatment of rheumatoid arthritis and osteoarthritis, now also evaluated as a potent anticancer drug. This system is unique as it enables encapsulation loads >100-fold higher than other β-casein/drug formulations, and does not require additives as do other formulations that have high loadings. This is combined with the ability to lyophilize the formulation without a cryoprotectant, long-term physical and chemical stability of the resulting powder, and fully reversible reconstitution of the structures by rehydration. The dry dosage form, in which >95% of the drug is encapsulated, meets the daily dose. Cryo-TEM and DLS prove that drug encapsulation results in micelle swelling, and X-ray diffraction shows that the encapsulated drug is amorphous. Altogether, our novel dosage form is highly advantageous for oral administration.
    Journal of Controlled Release 01/2012; 160(2):164-71. · 7.63 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Amphiphilic block copolymers and mixtures of amphiphiles find broad applications in numerous technologies, including pharma, food, cosmetic and detergency. Here we report on the interactions between a biological charged diblock copolymer, β-casein, and a synthetic uncharged triblock copolymer, Lutrol F-127 (EO(101)PO(56)EO(101)), on their mixed micellization characteristics and the micelles' structure and morphology. Isothermal titration calorimetry (ITC) experiments indicate that mixed micelles form when Lutrol is added to monomeric as well as to assembled β-casein. The main driving force for the mixed micellization is the hydrophobic interactions. Above β-casein CMC, strong perturbations caused by penetration of the hydrophobic oxypropylene sections of Lutrol into the protein micellar core lead to disintegration of the micelles and reformation of mixed Lutrol/β-casein micelles. The negative enthalpy of micelle formation (ΔH) and cooperativity increase with raising β-casein concentration in solution. ζ-potential measurements show that Lutrol interacts with the protein micelles to form mixed micelles even below its critical micellization temperature (CMT). They further indicate that Lutrol effectively masks the protein charges, probably by forming a coating layer of the ethyleneoxide rich chains. Small-angle X-ray scattering (SAXS) and cryogenic-transmission electron microscopy (cryo-TEM) indicate relatively small changes in the oblate micellar shape, but do show swelling along the small axis of β-casein micelles in the presence of Lutrol, thereby confirming the formation of mixed micelles.
    Physical Chemistry Chemical Physics 11/2010; 13(8):3153-60. · 3.83 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The LCST phase-transition of aqueous PNIPA solutions in rising concentrations of the strong chaotropic salt KSCN was studied microcalorimetrically by DSC and apparently for the first time by ITC. An endothermic (entropy driven) binding of KSCN onto PNIPA was observed, explained by electrostatic perturbation of hydrophobic hydration by adsorbed ions. A good fit was found for the one-type-of-sites binding model, and the binding affinity increased with rising temperature from 15 to 20 °C but decreased at 25 °C. DSC measurements emphasized the lowering and broadening of the endothermic peak of PNIPA phase-transition with rising KSCN concentration, explained by reduced cooperativity of coil-to-globule collapse with increased heterogeneity along the polymer chain, caused by salt adsorption. A hysteresis was observed between heating and cooling DSC peaks, which decreased asymptotically with rising KSCN concentration, further supporting that binding occurs. This work provides new insights into the mechanisms of chaotropic salt effects on polymers and biopolymers in aqueous solutions.
    Macromolecules. 12/2009; 43(1).
  • [Show abstract] [Hide abstract]
    ABSTRACT: Protein stability in aqueous solutions is important in numerous fields, particularly biotechnology and food-science. To shed new light on the protective effect of carbohydrates on proteins, we studied saccharide-structure effects in aqueous solutions on the coil-to-globule transition occurring at the lower critical solution temperature (LCST) of poly-N-isopropylacrylamide (PNIPA), an isomer of polyleucine, as a simple model representing certain key behaviors of proteins (e.g., denaturation/renaturation). We systematically selected sugars and polyols to relate structural and physical characteristics of these carbohydrates to their effect on PNIPA solutions. Using isothermal titration-microcalorimetry, we showed that no significant binding of saccharides to the polymer occurs. Using micro-DSC, we studied the decreasing polymer LCST temperature with rising carbohydrate concentration. Beyond the expected observation that steric exclusion is important, we observed previously-unreported significant differences among the effects of isomeric aldohexoses and also among the effects of isomeric diglucoses on PNIPA LCST. We found good correlation between the sugar hydration number and its effect on LCST. We conclude that the larger and denser the hydrated cluster a carbohydrate forms, the worse a cosolvent is for the polymer, and the stronger it's lowering effect of the coil-to-globule transition. Such favoring of the compact globule state provides a protective effect against denaturation of globular proteins. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2307–2318, 2008
    Journal of Polymer Science Part B Polymer Physics 09/2008; 46(21):2307 - 2318. · 2.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: beta-Casein is one of the main proteins in milk, recently classified as an intrinsically unstructured protein. At neutral pH, it is composed of a highly polar N-terminus domain and a hydrophobic C-terminus tail. This amphiphilic block-copolymer-like structure leads to self-organization of the protein monomers into defined micelles. Recently, it has been shown that at room temperature, beta-casein also self-organizes into micelles in an acidic environment, but the effect of temperature on the micelles' formation and properties at the low pH regime were not explored. In the present study, we used two complementary techniques, cryogenic-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS), to characterize at high-resolution the micelles' shape, dimensions, and aggregation numbers and to determine how these properties are affected by temperature between 1 and 40 degrees C. Two different regimes were studied: highly acidic pH where the protein is cationic, and neutral pH, where it is anionic. We found that flat disk-like micelles with low aggregation numbers formed at low temperature in the two pH regimes. Close to neutral pH increase in temperature involves a transition in the micelles' shape and dimensions from flat disks to bulky, almost spheroidal micelles, coupled with a sharp increase in the micelles' aggregation number. In contrast, no effects on the micelles' morphology or aggregation number were detected in the acidic environment within the entire temperature range studied. The self-organization into disk micelles and the lack of effect of temperature in the acidic environment are linked to the unstructured character of the protein and to the charge distribution map. The latter indicates that below the isoelectric pH (pI), beta-casein loses the distinct separation of hydrophobic and hydrophilic domains, thereby suggesting that it may no longer be considered as a classical head-tail block-copolymer amphiphile as in neutral pH.
    Langmuir 05/2008; 24(7):3020-9. · 4.38 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Beta-casein is an intrinsically unstructured amphiphilic protein that self-assembles into micelles at neutral pH. This paper reports that beta-casein self-organizes into micelles also under acidic conditions. The protein association behavior and micelle characteristics at pH 2.6, well below the p I, are presented. The pH was found to strongly affect the micelle shape and dimensions. Cryogenic transmission electron microscopy (cryo-TEM) experiments revealed disk-like micelles of 20-25 nm in length and approximately 3.5 nm in height in acidic conditions. An aggregation number of 6 was determined by sedimentation equilibrium under these conditions. Isothermal titration calorimetry experiments verified the association below the p I and allowed determination of the micellization enthalpy, the critical micellar concentration, and the micellization relative cooperativity (MR). Small-angle X-ray scattering results at concentrations below the critical micellization concentration (CMC) suggest that the monomeric protein is likely in a premolten globule state at low pH. Calculations of the protein charge at acidic and neutral pH reveal a similar high net charge but considerable differences in the charge distribution along the protein backbone. Overall the results show that beta-casein is amphiphilic at low pH, but the distribution of charge along the protein chain creates packing constraints that affect the micelle organization, leading at concentrations above the CMC to the formation of disk micelles.
    Journal of Agricultural and Food Chemistry 04/2008; 56(6):2192-8. · 2.91 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Truncation and acylation were combined to investigate the broad-spectrum bactericidal and hemolytic peptide S4(1-15). Substitution of up to seven residues with dodecanoic acid (C(12)) gradually led to specific antipseudomonal activity: out of 40 bacterial strains tested in vitro, C(12)-S4(8-15) displayed similar minimal inhibitory concentrations (MICs) as S4(1-15) against Pseudomonas aeruginosa sp. (identical MIC(90)) but was practically inactive against most other bacteria or erythrocytes. Surface plasmon resonance and isothermal titration calorimetry experiments revealed the binding properties of S4(1-15) to be consistent with its nonselective activities, while discriminative activities of C(12)-S4(8-15) correlated with high binding affinity to a membrane containing pseudomonal lipopolysaccharides and with lower affinities to membranes containing nonpseudomonal lipopolysaccharides or cholesterol. Various mechanistic studies failed to detect significant differences in secondary structure, bactericidal kinetics, or ability to perturb the cytoplasmic membrane, pointing to a similar mode of action.
    Chemistry & Biology 02/2007; 14(1):75-85. · 6.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Teucrium polium L. (Lamiaceae) (RDC 1117) is a medicinal plant whose species have been used for over 2000 years in traditional medicine due to its diuretic, diaphoretic, tonic, antipyretic, antispasmodic and cholagogic properties. The therapeutic benefit of medicinal plants is often attributed to their antioxidant properties. We previously reported that an aqueous extract of the leaves and stems of this plant could inhibit iron-induced lipid peroxidation in rat liver homogenate at concentrations that were not toxic to cultured hepatic cells. Others have reported that organic extracts of the aerial components of this plant could inhibit oxidative processes. Against this background, we felt further investigation on the antioxidant action of the extract of T. polium prepared according to traditional Arab medicine was warranted. Accordingly, we assessed (i) its ability to inhibit (a) oxidation of beta-carotene, (b) 2,2'-azobis(2-amidinopropan) dihydrochloride (AAPH)-induced plasma oxidation and (c) iron-induced lipid peroxidation in rat liver homogenates; (ii) to scavenge the superoxide (O2*-) radical and the hydroxyl radical (OH(*)); (iii) its effects on the enzyme xanthine oxidase activity; (iv) its capacity to bind iron; and (v) its effect on cell glutathione (GSH) homeostasis in cultured Hep G2 cells. We found that the extract (i) inhibited (a) oxidation of beta-carotene, (b) AAPH-induced plasma oxidation (c) Fe(2+)-induced lipid peroxidation in rat liver homogenates (IC(50) = 7 +/- 2 mug ml(-1)); (ii) scavenged O2*-(IC(50) = 12 +/- 3 mug ml(-1)) and OH(*) (IC(50) = 66 +/- 20 mug ml(-1)); (iii) binds iron (IC(50) = 79 +/- 17 mug ml(-1)); and (iv) tended to increase intracellular GSH levels resulting in a decrease in the GSSG/GSH ratio. These results demonstrate that the extract prepared from the T. polium possesses antioxidant activity in vitro. Further investigations are needed to verify whether this antioxidant effect occurs in vivo.
    Evidence-based Complementary and Alternative Medicine 10/2006; 3(3):329-38. · 1.72 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The association behavior, critical micellization concentration (CMC), and enthalpy of demicellization (DeltaHdemic) of bovine beta-casein were studied, for the first time by isothermal titration calorimetry, in a pH 7.0 phosphate buffer with 0.1 ionic strength and in pure water. In the buffer solutions, the CMC decreased asymptotically from 0.15 to 0.006 mM as the temperature was raised from 16 to 45 degrees C. DeltaHdemic decreased with increasing temperature between 16 and 28 degrees C but increased from 28 to 45 degrees C. Thermodynamic analysis below 30 degrees C is consistent with the Kegeles shell model, which suggests a stepwise association process. At higher temperatures, this model exhibits limitations, and the micellization becomes much more cooperative. The CMC values in water, measured between 17 and 28 degrees C, decreased with increasing temperature and, expectedly, were higher than those found in the buffer solutions. beta-Casein micelles were visualized and characterized, for the first time in their hydrated state, using advanced digital-imaging cryogenic transmission electron microscopy. The images revealed small, oblate micelles, about approximately 13 nm in diameter. The micelles shape and dimensions remained nearly constant in the temperature range of 24-35 degrees C.
    Journal of Agricultural and Food Chemistry 08/2006; 54(15):5555-61. · 2.91 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Mirror-image asymmetric molecules, i.e., chiral isomers or enantiomers, are classically considered as chemically identical. Recent studies, however, have indicated that parity violation by the nuclear weak force induces a tiny energy difference between chiral isomers. Upon combination with a massive amplification process, expansion of this difference to a detectable macroscopic level may be achieved. Yet, experimental tests of this possibility, where one enantiomer is compared to the other in solution, are hampered by the possible presence of undetectable impurities. In this study we have overcome this problem by comparing structural and dynamic features of synthetic D- and L-polyglutamic acid and polylysine molecules each of 24 identical residues. In these water-soluble polypeptides helix formation is an intramolecular autocatalytic process amplified by each turn, which is actually unaffected by low level of putative impurities in the solvent. The helix and random coil configurations and their transition were determined in this study by circular dichroism (CD) and isothermal titration calorimetry (ITC) in water and deuterium oxide. Distinct differences in structure and transition energies between the enantiomeric polypeptides were detected by both CD and ITC when dissolved in water. Intriguingly, these differences were by and large abolished in deuterium oxide. Our findings suggest that deviation from physical invariance between the D- and L-polyamino acids is induced in part by different hydration in water which is eliminated in deuterium oxide. Based on the recent findings by Tikhonov and Volkov (V. I. Tikhonov and A. A. Volkov, Science 2002, 296, 2363) we suggest that ortho-H(2)O, which constitutes 75% of bulk H(2)O, has a preferential affinity to L-enantiomers. Differential hydration of enantiomers may have played a role in the selection of L-amino acids by early forms of life.
    Physical Chemistry Chemical Physics 02/2006; 8(3):333-9. · 3.83 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In response to increased popularity and greater demand for medicinal plants, a number of conservation groups are recommending that wild medicinal plants be brought into cultivation systems. We collected four medicinal herbs Cichorium pumilum, Eryngium creticum, Pistacia palaestina and Teucrium polium used in traditional Arab medicine for greenhouse cultivation to assess the effects of different fertilization regimes on their growth and antioxidant activity. Wild seedlings were collected and fertilized with either 100% Hoagland solution, 50% Hoagland solution, 20% Hoagland solution or irrigated with tap water. Plant height was measured and the number of green leaves and branches counted weekly. Thereafter, the aboveground parts of plants were harvested for preparing a water-soluble powder extracts of which antioxidant activity was measured by their ability to suppress the oxidation of beta-carotene. Of the fertilization regimes, we found either 20 or 50% Hoagland solution produced the most consistent response of the plant growth parameters. All powders prepared from the four wild growing plants inhibited oxidation of beta-carotene. Increasing the amount of fertilizer caused a significant concentration-dependent increase in antioxidant activity of the cultivated T. polium compared with the wild type. In contrast, increasing the amount of fertilizer caused a significant concentration-dependent reduction in the antioxidant activity of powders prepared from the cultivated E. creticum when compared with wild plants. Our results showed that cultivation success should not rely solely on parameters of growth but should incorporate assessment related to indices of therapeutic potential.
    Evidence-based Complementary and Alternative Medicine 01/2006; 2(4):549-56. · 1.72 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The medicinal use of extracts prepared from plant parts of the genus Crataegus dates back to ancient times. Furthermore, it has been proposed that its antioxidant constituents account for its beneficial therapeutic effects. A decoction of leaves and unripe fruits from Crataegus aronia syn. azarolus (L) (Rosaceae), the indigenous Israeli hawthorn, is used to treat cardiovascular diseases, cancer, diabetes and sexual weakness in Arab traditional medicine. Because laboratory data on the bioactivity of extracts prepared from the indigenous Israeli hawthorn is lacking, we evaluated the antioxidant and cytotoxic potentials of an extract prepared from leaves and unripe fruits in a variety of cell and cell-free in vitro assays. The antioxidant assays measured: (a) its ability to inhibit (i) oxidation of beta-carotene, (ii) 2,2'-azobis(2-amidino-propan) dihydrochloride (AAPH)-induced plasma oxidation and (iii) iron-induced lipid peroxidation in rat liver homogenates; (b) its ability to scavenge the superoxide (O2-) radical; (c) its effects on the enzyme xanthine oxidase (XO) activity; (d) its effect on the redox state of glutathione (GSH) in cultured Hep G2 cells. In addition, we also evaluated the effects of the extract on cell membrane integrity and mitochondrial respiration in cultured Hep G2 cells. Water-soluble extracts inhibited (1) oxidation of beta-carotene, (2) AAPH-induced plasma oxidation and (3) Fe(2+)-induced lipid peroxidation in rat liver homogenates. In addition, the extract (4) is an efficient scavenger of the O2- (5) increases intracellular GSH levels and (6) is not cytotoxic. Accordingly, we propose that the therapeutic benefit of Crataegus aronia can be, at least in part, attributed to its effective inhibition of oxidative processes, efficient scavenging of O2- and possible increasing GSH biosynthesis.
    Journal of Ethnopharmacology 11/2005; 101(1-3):153-61. · 2.76 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Ethnopharmacological surveys conducted among herbal practitioners of traditional Arab medicine in Israel and the Palestinian area have revealed a large number of indigenous plant species are used as sources of their herbal therapies. Some of these herbal therapies are used to treat liver disease, jaundice or diabetes, conditions in which oxidative stress is prominent. No laboratory data on the bioactivity of herbal medicines in these settings exist in traditional Arab medicine. We hypothesized that the beneficial effect of these plants might be due to their antioxidant properties. Accordingly, we selected eight plants used to treat these two conditions and assessed their antioxidant potential by measuring their ability to suppress the extent of iron-induced lipid peroxidation in rat liver homogenates and their potential toxicity by evaluating their effects on mitochondrial respiration and cell membrane integrity in cultured PC12 and HepG2 cells. We found that all the extracts can suppress iron-induced lipid peroxidation and are not toxic. Of these extracts, those prepared from Teucrium polium and Pistacia lentiscus were the most effective in suppressing iron-induced lipid peroxidation. Further investigations are now needed to establish the exact mechanism of action and identify the active bio-ingredient(s) of each extract in order to explain their therapeutic efficacy.
    Journal of Ethnopharmacology 06/2005; 99(1):43-7. · 2.76 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The effect of two strong salting-out salts (Na2SO4 and K2SO4) on the temperature-induced phase-separation process in aqueous solutions of poly(N-isopropylacrylamide) (PNIPA) was examined by attenuated total reflectance/Fourier transform infrared spectroscopy, differential scanning calorimetry, and viscosity measurements. On the basis of these measurements, a detailed scenario of the phase-separation process was deduced. The phase-separation scenario of solutions containing PNIPA and water was altered in the presence of sulfate ions. Here, the sulfate ions induced partial intrachain collapse, manifested by a relatively compact structure well below the lower critical solution temperature. This led to a more gradual, smooth phase transition, with temperature-resolved intrachain collapse and interchain aggregation and a lesser extent of hysteresis. Although at the macrolevel one may not be able to differentiate among various scenarios altering the solvent into a poor solvent, the aforementioned microlevel measurements provided a way to expose the difference between raising the temperature and adding cosolutes. Follow-up studies on the effect of salting-in salts will be presented. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 33–46, 2004
    Journal of Polymer Science Part B Polymer Physics 12/2003; 42(1):33 - 46. · 2.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The swelling of polyacrylamide (PAAm) gels increased with rising glucose concentrations, and so did the osmotic pressure of the soluble polymer and its intrinsic viscosity. A Flory–Huggins-based model for the osmotic pressure of a nonionic hydrophilic polymer in a ternary solution consisting of a main solvent, a polymer, and a nondissociating low-molecular-weight cosolute was developed and examined. The model-calculated values were in reasonably good agreement with experimental results for the water–PAAm–glucose system studied when PAAm–water and glucose–water interaction coefficients from the binary systems were used, and only the PAAm–glucose interaction coefficient was adjusted. Its negative value suggested a favorable interaction of glucose and PAAm, supporting the notion of glucose being a good cosolvent for PAAm. Isothermal titration microcalorimetry results showed no evidence for the binding of glucose to PAAm, but an exothermic interaction was indicated between glucose and PAAm. Microcalorimetrically determined enthalpic contributions to the Flory–Huggins interaction coefficients showed enthalpically favorable binary interactions, particularly the enthalpic component of the PAAm–glucose interaction coefficient (χH23), which was slightly negative. The enthalpically favorable interaction between glucose and PAAm may explain the increased osmotic pressure of PAAm in glucose solutions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3053–3063, 2003
    Journal of Polymer Science Part B Polymer Physics 10/2003; 41(23):3053 - 3063. · 2.22 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The swelling of poly(acrylamide) (PAAm) gels and the osmotic pressure of linear PAAm in aqueous solutions were predominantly affected by anion type and increased according to the lyotropic series ranking of sodium halide anions: F− < (H2O) < Cl− < Br− < I−. The osmotic pressure of PAAm in all examined salt solutions followed the scaling theory, with an exponent of 2.3 ± 0.1. In solutions of a sodium halide series, the value of the pre-exponential factor seemed to depend on salt concentration, anion radius, and the apparent “anionic-portion radius” of the water molecule. This radius, extracted from the literature data, marks a transition point of the anion radius effect. Larger anions increase the osmotic pressure of PAAm more significantly as their concentration increases and vice versa. The effects of the anions on the osmotic pressure of PAAm are related to their preferential interactions with the polymer. Iodide, which increased the osmotic pressure of PAAm with respect to its value in pure water, seemed to preferentially adsorb onto the polymer with a binding constant of Kb = 9.7 ± 2.0 M−1 determined by isothermal titration microcalorimetry. However, fluoride, which decreased the osmotic pressure, was preferentially repulsed. The mechanisms of attraction and repulsion were attributed to ion-water-polymer interactions and the solvent quality of the hydrated ions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 508–519, 2003
    Journal of Polymer Science Part B Polymer Physics 01/2003; 41(5):508 - 519. · 2.22 Impact Factor
  • Ludmila Abezgauz, Irina Portnaya, Dganit Danino
    [Show abstract] [Hide abstract]
    ABSTRACT: Polyoxyethylene cholesteryl ethers (ChEOm) are a class of nonionic surfactants with an “inverse” structure: rigid hydrophobic tail and long hydrophilic head groups. These surfactants are nontoxic, biodegradable and used in cosmetic and pharmaceutical industries. Unexpectedly for nonionic surfactants, several reports indicated that the viscosity of low concentration solutions of ChEOm increase several orders of magnitude upon raise of temperature or upon mixing with polyoxyethylene dodecyl ether (C12EOm) surfactants [1, 2]. The micellar assembly behavior of these systems has not yet adequately studied.