bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and surface‐active properties of telomer‐type anionic surfactants from maleic anhydride
Authors: Yoshimura Tomokazu , Koide Yoshifumi , Shosenji Hideto , Esumi Kunio
Published: November 2006

Maleic acid alkyl ester and N‐alkyl maleamic acid monomers (RnMa and RnMaAm; n is alkyl chain length; n=6, 8, 10, 12, 14) were synthesized by the reaction of maleic anhydride with alkyl alcohol or alkylamine. The telomerization of RnMa or RnMaAm in the presence of alkanethiol as a chain transfer agent gave telomer‐type anionic surfactants (xRnMa, xRnMaAm; x is total average number of alkyl chains; x=2.8–3.3) having multialkyl chains and multicarboxylate groups. Their surface‐active properties were investigated by several techniques such as surface tension, foaming property, and emulsification power measurements. Critical micelle concentrations (CMC) of xRnMa were 1/110–1/14 of those of RnMa with the same alkyl chain length. xRnMa and xRnMaAm gave higher efficiencies in lowering the surface tension than RnMa and RnMaAm in aqueous solutions. In particular, the surface tension of 3.2R12MaAm was 24.4 mN m−1 at the CMC. Foaming abilities and foam stabilities of xRnMa and xRnMaAm were higher than those of RnMa and RnMaAm. The addition of 300 ppm of Ca2+ to the aqueous solutions rendered the telomers less surface active. Shaking the aqueous solutions of telomers with toluene emulsified them. The highly stable oil‐in‐water type emulsion was formed by using 3.0R10MaAm and 3.2R12MaAm, and the degree of emulsification was kept at a level of about 80% after 60 min of standing. Thus, telomer‐type surfactants showed excellent surface activities that were superior to the corresponding monomers as well as to conventional surfactants. The relationship between alkyl chain length of the telomers and the properties of surface tension, foaming, and emulsification was unclear.
Kinetics of precipitation of surfactants. III. Atomic force microscopy of precipitate crystals
Authors: Rodriguez Cheryl H. , Yuan Wei‐Li , Scamehorn John F. , O'Rear Edgar A.
Published: November 2006

The overall time required for precipitation to occur can increase dramatically for surfactant mixtures compared to single components. Atomic force microscopy (AFM) has been used in this study to examine the precipitated surfactant crystals, which gives insight into both the thermodynamics and kinetics of surfactant precipitation. Calcium dodecyl sulfate, Ca(DS)2 shows regular, layered growth that is consistent with a screw‐dislocation crystallization mechanism. Calcium octylbenzene sulfonate, Ca(OBS)2, forms crystals with uneven, jagged edges. At high magnification, the head groups of both Ca(DS)2 and Ca(OBS)2 show hexagonal packing. For mixtures that have surprisingly slow precipitation kinetics, the jagged Ca(OBS)2 crystals were observed to grow on the layered Ca(DS)2 crystals. Other surfactant mixtures that exhibited a stepwise rate curve formed crystals with incomplete layers and holes that are not observed with pure surfactants. In general, this type of crystal formation can occur when an impurity is present, which in this case is most likely the second surfactant. This work indicates that interruption of crystal growth by crystallization of a dissimilar supersaturated surfactant onto the first crystal is one explanation for the slower precipitation of surfactant mixtures compared to single surfactants. Entrapment of the nonprecipitating surfactant (inclusion) in the forming crystal of the precipitating surfactant in mixed surfactant systems is another mechanism responsible for the reduction in precipitation rate.
Comparison of two methods to estimate the standard free energy of adsorption
Authors: Miller R. , Fainerman V. B. , Möhwald H.
Published: November 2006

To determine the increment of the standard free energy per methylene group ΔG0CH2 for ionic and nonionic surfactants, two calculation methods are proposed. One procedure is based on the adsorption energy parameter of the respective adsorption isotherm, and the second on the critical micelle concentration. Experimental surface tension isotherms for two homologous series, a nonionic (CnBHB) and an ionic (CnTAB) surfactant, are used to demonstrate how the methods work. As adsorption isotherms, the Frumkin and the reorientation models provide a rather good description for both surfactants. The free energy increments ΔG0 obtained from the two methods are the same if the reorientation model is used, but the Frumkin model gives different results.
Synthesis and chemical hydrolysis of surface‐active esters
Authors: Stjerndahl Maria , Holmberg Krister
Published: November 2006

A series of four homologous pure nonionic surfactants, all monoesters of tetra(ethylene glycol), were synthesized. The ester surfactants varied in the degree of substitution on the α‐carbon of the acyl chain, from no substitution to 2‐methyl, to 2‐ethyl, and on to 2,2‐dimethyl. All surfactants were based on C8‐acids except the 2‐methyl‐substituted, which was based on a C7‐acid. The ester surfactants were characterized by critical micelle concentration (CMC) and cloud point. Base‐catalyzed hydrolysis was investigated by using 1H NMR and tensiometry. The surfactants showed a pronounced difference in hydrolytic reactivity; the nonsubstituted surfactant was 90 times more reactive than the disubstituted, and the reactivity of the methyl‐substituted surfactant was 14 times more reactive than the ethyl‐substituted. Hydrolysis studies above the CMC revealed that the ester bond of the aggregated surfactant is protected from attack by hydroxide ions; thus, only surfactants in monomeric form are being cleaved.
Dye‐Surfactant interaction in the premicellar region
Authors: Gokturk Sinem , Tuncay Melda
Published: November 2006

The interaction of safranin‐O (SO), a cationic dye, with anionic surfactants [sodium dodecylsulfate (SDS) and sodium dodecylsulfonate (SDSo]) having the same hydrophobic group but different polar groups was studied spectrophotometrically in the premicellar region far below the critical micelle concentration in aqueous media using the method of continuous variations, also called Job's Method. This method was applied to determine the equilibrium complex formation constant (K) as well as the molecular complex formation ratio. Both SDS and SDSo formed stable associations with SO, and the molecular complex formation ratio was determined as 1:1. The data obtained from Job's Method indicated that the equilibrium complex formation constant of SDS is higher than that of SDSo. We also studied the influence of cosolvents such as methanol, dimethylformamide (DMFA), and dioxan (DX) on molecular complex formation between SDS and SO, and observed that the presence of cosolvents inhibited molecular complex formation. This inhibitory effect of cosolvents on molecular complex formation followed the order of methanol>DMFA>DX.
Role of quaternary bromides in changing the solubilization site of n‐heptylamine in cationic micellar solutions
Authors: Kumar Sanjeev , Sharma Daksha , Kabir‐ud‐Din
Published: November 2006

Newtonian flow conditions were adopted to take viscosity measurements at 30°C of solutions of cationic surfactants (cetyltrimethylammonium bromide, C16TAB, and tetradecyltrimethylammonium bromide, C14TAB) with the addition of n‐heptylamine (C7NH2) and quaternary salts (tetra‐n‐propylammonium bromide, Pr4NBr; tetra‐n‐butylammonium bromide, Bu4NBr; tetraamylammonium bromide, Am4NBr; tetra‐n‐octylammonium bromide, Oc4NBr; tetra‐n‐butylphosphonium bromide, Bu4PBr; tetraphenylphosphonium bromide, Φ4PBr; n‐propyltriphenylphosphonium bromide, PrΦ3PBr3) by having either a fixed C7NH2 or salt concentration and varying the other. Systems containing a comparatively higher Bu4NBr content showed a dramatic decrease in viscosity at higher C7NH2 concentration. Further, the viscosity‐salt concentration profiles of 0.1 M C16TAB solutions containing fixed C7NH2 concentrations showed a peaked behavior. The peak positions and salt contents at the peaks were dependent on the length of the alkyl part of the particular salt and the connecting atom (N or P) but independent of the nature of the surfactant and C7NH2 concentration. The behavior is discussed in the light of a change in the solubilization site of C7NH2 caused by the presence of quaternary salts. Cavities in the quaternary salts present in the bulk solvent are proposed to be the new sites of solubilization.
Treating emulsified waste containing mineral oils and alkylphenolethoxylate by membrane and acid‐heating processes
Authors: Miyagi Atsushi , Nakajima Mitsutoshi
Published: November 2006

We applied a membrane process to treat emulsified industrial waste with mineral oils and alkylphenolethoxylate (APE). Besides the membrane process, we also investigated acid‐heating processes for easy introduction into small factories. The present studies were carried out using factory waste for a practical application. In the NTU‐2120 membrane process, 99.0 to 99.1% of total organic carbon (TOC) and 97.1 to 98.2% of chemical oxygen demand (COD) were removed from the waste, demonstrating the efficacy of the waste treatment. Permeate fluxes were reduced by 60 to 80% until the volume reduction factor reached 10. The permeate flux was governed by the gel polarization model, and the specific resistance of the gel layer became greater with pressure. Regeneration of the used membrane by the back‐pressure wash method completely restored the membrane capacities. The acid‐heating process (pH<3, temperature >70°C) reduced TOC by 96.0% and COD by 92.3%, demonstrating waste treatment efficacy similar to that of the membrane process.
Phase inversion temperatures of triton X‐100/1‐butanol/hydrocarbon/water systems
Authors: Bayrak Yuksel , Iscan Mehmet
Published: November 2006

The formation of a water‐in‐oil (w/o) microemulsion in Triton X‐100/1‐butanol/alkane/water systems was investigated at 25.0±0.1°C. Phase inversion temperatures in hydrocarbon‐water microemulsions stabilized with Triton X‐100 were determined for different hydrocarbons. It was found that the more soluble the alkane (oil), functioning as a nonionic emulsifier, the lower was the phase inversion temperature, above which oil‐in‐water type microemulsions invert to w/o type. The effect of the presence of cosurfactant was studied. No phase inversion was observed in the absence of cosurfactant. The effect on phase inversion temperature of decreasing or increasing the temperature was evaluated. By definition, phase inversion was not affected by different temperatures.
Liquid chromatography‐mass spectrometry of nonionic surfactants using electrospray ionization
Authors: Zhu JingKe
Published: November 2006

The analysis of nonionic surfactants was investigated by reversed‐phase liquid chromatography with mass spectrometry detection. On a C18 column, separation was achieved on the basis of chain lengths of both alkyl and ethoxy groups in a CH3CN/CH3OH/H2O/HAc solvent system. Peaks were identified by electrospray mass spectrometry.
Enzyme‐based detergent formulas for fatty soils and hard surfaces in a continuous‐flow device
Authors: Jurado E. , Bravo V. , Núñez‐Olea J. , Bailón R. , Altmajer‐Vaz D. , Garíia‐Román M. , Fernández‐Arteaga A.
Published: November 2006

The present work analyzes the effect of incorporating a lipolytic enzyme (Lipolase® 100L) into detergent formulas for washing fatty soils on hard surfaces. The experimental device, which is called a “bath‐substrate‐flow” device, uses a continuous flow on a substrate (glass spheres) soiled with triolein. Washing tests were done using only the enzyme and changing both its concentration and the temperature of the process. The results showed that, in the presence of lipase, soil removal was achieved through three consecutive mechanisms: (i) fundamental devoval of the soil by the bath flow through the experimental device; (ii) emulsion of the soil in the washing medium; and (iii) enzymatic hydrolysis of the dispersed soil. Different commercial surfactants were used, and detergency was evaluated in the absence and presence of lipase. The use of surfactant formulas with the lipolytic enzyme showed a positive effect of the enzyme on the detergency values registered with the fatty alcohol ethoxylate surfactants Findet® 10/15 and Findet 1214N/23, and with the anionic surfactant linear alkylbenzene sulfonate. The commercial surfactants Glucopon® 600, Glucopon 650, Findet 10/18, and Findet Q/21.5NF alone each presented high detergency values for fatty soils, and the effect of the incorporation of the lipase was not significant.
Synthesis, characterization, and surface properties of sulfoxylated methyl esters
Authors: Cohen L. , Trujillo F.
Published: November 2006

Sulfoxidation of fatty methyl esters with SO2, O2, and ultraviolet light of appropriate wavelength has led to a synthesis of sodium methyl ester sulfonates known as Φ‐MES. The designation of Φ refers to the random positioning of SO3 in the alkyl chain. This investigation describes for the first time the operating conditions necessary to produce these new anionic surfactants as well as the analytical methods used in their isolation, analysis, identification. Some surface properties are discussed as well.
Utilization of acid oils in making surface‐active compounds by lipase‐catalyzed hydrolysis and esterification reactions
Authors: Basu S. , Bhattacharyya D. K.
Published: November 2006

Nonionic surface‐active molecules were made from acid oils such as mustard, sunflower, rice bran, soybean, coconut, and polyethylene glycols (PEG) of varying molecular weights (200, 300, 400, 600), using processes based on lipasecatalyzed hydrolysis with Candida cylindracea lipase and esterification with Mucor miehei lipase. Both the PEG molecular weight and the acid oil influence the yield of ester. Molar concentration of reatants also influences the rate and yield of ester. Surface tension values of ester products reveal that maximal lowering of surface tension of water occurs in the case of PEG 600 and coconut acid oil ester. This work demonstrates an important technological advance in the synthesis of nonionic surfactants of the alkyl ethoxylate type from a variety of acid seed oils in high yields by using lipase technology involving first hydrolysis and then esterification with another lipase.
The application of surfactant deflocculants to superconceptrated household and industrial laundry liquids
Authors: Clapperton Richard M.
Published: November 2006

A Structured Surfactant System comprises a readily pourable surfactant phase in aqueous solution which is capable of long‐term suspension of insoluble builder particles. First‐generation structured systems have been limited to soluble electrolyte concentrations that do not cause strong flocculation of the surfactant phase, typically a maximum of approximately 15% by weight electrolyte. As a direct consequence, the maximal surfactant content of structured systems has also been limited to about 30%. This paper reports the recent development of deflocculation technology, which has enabled the total active concentration in structured systems to be increased to as high as 70% by weight. Deflocculation of model structured surfactant systems by alkyl thiol polyacrylates and alkyl polyglucosides has been investigated by rheometry and optical microscopy. Viscosity changes in model detergent systems have been determined as a function of deflocculant headgroup size and concentration. These have been related to the process of deflocculation by a study of the microscopic appearance and storage stability of the same model systems. Interlamellar spacing of surfactant vesicles in a deflocculated model structured system has then been determined as a fenction of electrolyte concentration by the technique of small angle X‐ray scattering. It has been shown that surfactant vesicle shrinkage in the presence of high electrolyte concentration and a deflocculant can be used to formulate a superconcentrated liquid system.
Solubilization of phosphatidylcholine unilamellar liposomes caused by alkyl glucosides
Authors: de la Maza A. , Lopez O. , Baucells J. , Gonzalez P. , Parra J. L.
Published: November 2006

Solubilizing alterations caused by a series of alkyl glucosides (alkyl chain lengths ranging from C8 to C12) in phosphatidylcholine (PC) unilamellar liposomes were investigated. Surfactant‐to‐phospholipid molar ratios (Re) and bilayer/aqueous phase partition coefficients (K) were determined by monitoring changes in static light scattering (SLS) of the system during solubilization. At the two interaction levels investigated (surfactant concentrations producing SLS values of 100 and 0% for each surfactant/PC system studied) the free surfactant concentration for each surfactant was always comparable to its critical micelle concentration (CMC). This indicates that liposome solubilization was mainly ruled by mixed micelle formation. A rise in CMC (or decrease in the surfactant alkyl chain length) resulted in an increase in the ability of these surfactants to saturate or solubilize PC liposomes and, inversely, in an abrupt decrease in their affinity with these bilayer structures. The overall balance of these opposite tendencies shows that the octyl glucoside had the highest ability to saturate and solubilize liposomes (lowest Re values), whereas the dodecyl glucoside exhibited the highest degree of partitioning into liposomes or affinity with bilayer structures (highest K values). From a practical viewpoint, the use of nonyl glucoside reduced approximately 2.5 times the concentration needed to saturate and solubilize 1.0 mM PC liposomes with respect to that needed using the conventional octyl glucoside.
Long‐term feeding of dietary oils alters lipid metabolism, lipid peroxidation, and antioxidant enzyme activities in a teleost (Anabas testudineus bloch)
Authors: Varghese Sheelu , Oommen Oommen V.
Published: November 2006

Anabas testudineus (climbing perch), average body weight 21±1 g, were maintained in culture tanks and fed a 35% protein feed plus an additional supplementation of three dietary oils (20% each of coconut oil, palm oil, or cod liver oil). Body weight gain was similar among all groups. However, several hepatic lipogenic enzymes such as malic enzyme (ME), NADP‐isocitrate dehydrogenase (ICDH), glucose‐6‐phosphate dehydrogenase (G6PDH), 6‐phosphogluconate dehydrogenase (6PGDH) and β‐hydroxy‐β‐methyl glutaryl CoA reductase (HMG CoA reductase) were assayed, and they responded differently. Hepatic ME and G6PDH activities showed a significant decrease in the coconut oil and palm oil groups, but there was no significant change in ICDH activity. The 6PGDH activities were reduced, whereas HMG CoA reductase activity was increased in the palm oil‐treated group. Cholesterol synthesis in the liver and muscle increased in the palm oil‐treated group, but liver phospholipids did not show any significant change in fish supplemented with oils rich in saturated fatty acids. Triacyl‐glycerol and free fatty acid concentrations were high in the coconut oil‐ and palm oil‐supplemented groups. Lipid peroxidation products such as thiobarbituric acid‐reactive substances and conjugated dienes decreased in the same two groups. Antioxidant potential was high in all groups as evidenced by increased activity of superoxide dismutase, glutathione peroxidase, and glutathione content. The results of this study indicate that in fish, dietary lipids depress hepatic lipogenic activity as well as lipid peroxidation products by maintaining high levels of antioxidant enzymes.
Polyunsaturated fatty acids and infant growth
Authors: Lapillonne Alexandre , Carlson Susan E.
Published: November 2006

Because of the rapid rate of growth during infancy, and the potentially deleterious effect of differences in the availability of dietary essential nutrients, growth is an important outcome variable in any study assessing a diet designed for infants. Nearly 10 yr after the first demonstration of reduced growth in preterm infants fed a fish oil‐enriched formula, there is very little additional information to confirm or refute the finding that long‐chain n−3 polyunsaturated fatty acid (LC‐PUFA) intake can modulate growth in infants. To evaluate the issue of a possible relationship between PUFA intake and growth of infants, we reviewed a total of 32 randomized studies, 13 in preterm infants and 19 in term infants. From the data published to date, it seems clear that long‐chain n−3 fatty acids can reduce growth achievement in preterm and term infants under some experimental conditions. However, the effect of n−3 PUFA supplementation on the growth of preterm and term infants appears to be minimal and of questionable clinical and/or physiologic relevance. Nonetheless, n−3 fatty acids have an effect on gene transcription, at least in some species, and this finding may provide important clues to the mechanism by which n−3 and n−6 fatty acids regulate growth.
Targeted disruption of peroxisomal proliferator‐activated receptor β (δ) results in distinct gender differences in mouse brain phospholipid and esterified FA levels
Authors: Rosenberger Thad A. , Hovda Jonathan T. , Peters Jeffrey M.
Published: November 2006

The peroxisomal proliferator‐activated receptor β (δ) (PPARβ) is a nuclear hormone receptor that is ubiquitously expressed and that regulates the transcription of genes involved in lipid metabolism. A homozygous PPARβ‐null mouse has been developed in which the ligand‐binding domain of the PPARβ receptor is disrupted. Analysis of brains from these animals shows that female null mice have 24 and 17% increases in plasmenylethanolamine and phosphatidylserine and a 9% decrease in the level of phosphatidylinositol when compared to controls. The phospholipid changes found in female null mice were associated with increased levels of esterified 18∶1n−9, 20∶1n−9, 20∶4n−6, and 22∶5n−3 FA in plasmenylethanolamine, 20∶1n−9 in phosphatidylinositol, and 18∶0, 18∶1n−9, 18∶3n−6, 20∶1n−9, and 20∶4n−6 in phosphatidylserine. Increased levels of esterified 18∶1n−9, 18∶2n−6, 18∶3n−6, and 20∶1n−9 were also found in the phosphatidylethanolamine fraction despite its cellular content remaining unchanged. Brain phospholipid content in male PPARβ‐null mice did not differ from controls, but increased levels of 20∶1n−9 in the phosphatidylinositol and 18∶1n−9 in the phosphatidylserine fractions were observed. No changes were found in the content of brain cholesterol, TAG, and FFA in either female or male PPARβ‐null mice. These data suggest that PPARβ is involved in maintaining FA and phospholipid levels in adult female mouse brain and provide strong evidence that suggests a role for PPARβ in brain peroxisomal acyl‐CoA utilization.
A convenient method for determination of the C20–22 PUFA composition of glycerolipids in blood and breast milk
Authors: Ichihara Ken'ichi , Waku Kanako , Yamaguchi Chiaki , Saito Kazumi , Shibahara Akira , Miyatani Shuichi , Yamamoto Kohei
Published: November 2006

A convenient method was developed for preparation of FAME in small amounts from glycerolipids of blood or breast milk. Initially, 0.04–0.06 mL blood or breast milk was spotted onto a small piece of filter paper (1.5×1.5 cm) that had been washed with acetone containing 0.05% 2,6‐di‐tert‐butyl‐p‐cresol (BHT). Fach piece, once it had dried, was put in a small test tube, to which 2 mL hexane and 0.2 mL 2 M KOH/methanol were added. After vigorous mixing or sonication for 2 min at room temperature, the solution was neutralized or acidified by the addition of a few drops of acetic acid. To the solution was added 2 mL H2O, and then the hexane layer that separated was concentrated to dryness in vacuo. The FAME obtained were analyzed by GC. The method was applicable to the analysis of a large number of blood and breast milk samples, and the arachidonate/(eicosapentaenoate +docosahexaenoate) ratios could be determined rapidly.
Nonpolar lipid composition ofChenopodium albumgrown in continuously cultivated and nondisturbed soils
Authors: Leicach S. R. , Grass M. A. Yaber , Corbino G. B. , Pomilio A. B. , Vitale A. A.
Published: November 2006

Chenopodium albumL. plants grown in continuously cultivated and in nondisturbed soils were compared in terms of the compositions of nonpolar extracts of the corresponding aerial parts. Both light petroleum ether extracts ofC. albumL. were analyzed by high‐performance thin‐layer LC, capillary GC, and capillary GC‐El‐MS. Further percolation and medium‐pressure LC, along with EI‐MS analysis, permitted the separation and identification of the chemical constituents. Differences were observed between mean contents of the chemical constituents ofC. albumL., with respect to nonpolar extracts, obtained from continuously cultivated and from nondisturbed soils, in particular in linear and branched long‐chain hydrocarbons, FA and their esters, and long‐chain linear alcohols and aldehydes. The most remarkable features of the disturbed soils were a pronounced increase in the amounts of linear hydrocarbons and a decrease in the relative proportions of FA.
Synthesis and isolation of trans‐7, cis‐9 octadecadienoic acid and other CLA isomers by base conjugation of partially hydrogenated γ‐linolenic acid
Authors: Delmonte Pierluigi , Roach John A. G. , Mossoba Magdi M. , Morehouse K. M. , Lehmann Lutz , Yurawecz Martin P.
Published: November 2006

CLA is of considerable interest because of reported potentially beneficial effects in animal studies. CLA, while not yet unambiguously defined, is a mixture of octadecadienoic acids with conjugated double bonds. The major isomer in natural products is generally considered to be cis‐9,trans‐11‐octadecadienoic acid (c9, t11), which represents >75% of the total CLA in most cases. Other isomers are drawing increased attention. The t7,c9 isomer, which is often the second‐most prevalent CLA in natural products, has been reported to represent as much as 40% of total CLA in milk from cows fed a high‐fat diet. The need for a reference material became apparent in a recent study directed specifically at measuring t7,c9‐CLA in milk, plasma, and rumen. A suitable standard mixture was produced by stirring 0.5 g of γ‐linolenic acid (all cis‐6,9, 12‐C18∶3) with 100 mL of 10% hydrazine hydrate in methanol for 2.5 h at 45°C. The solution was diluted with H2O and acidified with HCl. The resulting partially hydrogenated FA were extracted with ether/petroleum ether, dried with Na2SO4, and conjugated by adding of 6.6% KOH in ethlylene glycol and heating for 1.5 h at 150–160°C. Approximately 20 mg each of cis‐6, trans‐8; trans‐7, cis‐9; cis‐9, trans‐11; and rans‐10, cis‐12 were obtained along with other FA. Methyl esters (FAME) of these four cis/trans isomers were resolved by Ag+HPLC (UV 233) and partially resolved by GC/(MS or FID) (CP‐Sil 88). Treatment of these FAME with I2 yielded all possible cis/trans (geometric) isomers for the four positions 6,8; 7,9; 9,11; and 10,12.
Effects of specific CLA isomers on plasma fatty acid profile and expression of desaturases in humans
Authors: Thijssen Myriam A. M. A. , Malpuech‐Brugère Corinne , Gregoire Stéphane , Chardigny Jean Michel , Sébédio Jean Louis , Mensink Ronald P.
Published: November 2006

Human studies suggest that CLA changes metabolism, possibly through effects on mRNA expression of desaturase and elongase enzymes. In this respect, differential effects of the two most common dietary CLA isomers, cis‐9, trans‐11 (c9,t11) and trans‐10,cis‐12 (t10,c12) CLA, have hardly been studied. We therefore gave 25 healthy, overweight men and women daily for 6 wk a drinkable dairy product containing 3 g of oil that was rich in oleic acid. For the next 18 wk, the control group (n=7) continued to use this product, whereas the second (n=9) and third groups (n=9) received products with 3 g of purified c9,t11 CLA or t10,c12 CLA. For each gram of c9,t11 CLA consumed, the proportion in plasma phospholipids increased by 0.26%. For t10,c12 CLA, this value was 0.20%. The t10,c12 CLA isomer increased plasma TAG levels of conjugated 18∶3, whereas c9,t11 CLA increased those of both conjugated 18∶3 and 20∶3. In plasma phospholipids, the α9 desaturation index of 18∶0 (18∶1n−9/18∶0) was decreased by t10,c12 CLA (P=0.03 for diet effects), and the Δ6 desaturation index [(18∶3n−6+20∶3n−6)/18∶2n−6] was decreased by both CLA isomers (P<0.01 for diet effects). The Δ5 desaturation index (20∶4n−6/20∶3n−6) and Δ9 desaturation index of 16∶0 (16∶1n−7/16∶0) were not affected. No effects were seen on mRNA expression of desaturases and elongase in peripheral blood mononuclear cells (PBMC). We therefore conclude that incorporation of c9,t11 and t10,c12 CLA into plasma lipids reflects dietary intakes. Compared with oleic acid, Δ9 and Δ6 desaturation indices in plasma phospholipids are decreased after consumption of c9,t11 or t10,c12 CLA. Effects on desaturation indices were, however, not reflected by changes at the transcriptional level for the various desaturases and elongase enzymes in PBMC.
A study on the causes for the elevated n−3 fatty acids in cows' milk of alpine origin
Authors: Leiber Florian , Kreuzer Michael , Nigg Daniel , Wettstein Hans‐Rudolf , Leo Scheeder Martin Richard
Published: November 2006

The influence of grass‐only diets either from rye‐grass‐dominated lowland pastures (400 m above sea level) or botanically diverse alpine pastures (2000 m) on the FA profile of milk was investigated using three groups of six Brown Swiss cows each. Two groups were fed grass‐only on pasture (P) or freshly harvested in barn (B), both for two experimental periods in the lowlands and, consecutively, two periods on the alp. Group C served as the control, receiving a silage‐concentrate diet and permanently staying in the lowlands. Effects of vegetation stage or pasture vs. barn feeding on milk fat composition were negligible. Compared with the control, α‐linoleic acid (18∶3n−3) consumption was elevated in groups P and B (79%, P<0.001) during the lowland periods but decreased on the alp to the level of C owing to feed intake depression and lower 18∶3n−3 concentration in the alpine forage. Average 18∶3n−3 contents of milk fat were higher in groups, P and B than in C by 33% (P<0.01) at low and by 96% (P<0.001) at high altitude, indicating that 18∶3n−3 levels in milk were to some extent independent of 18∶3n−3 consumption. The cis‐9,trans‐11 CLA content in milk of grass‐fed cows was higher compared with C but lower for the alpine vs. lowland periods whereas the trans‐11, cis‐13 isomer further increased with altitude. Long‐chain n−3 FA and phytanic acid increased while arachidonic acid decreased with grass‐only feeding, but none of them responded to altitude. Grass‐only feeding increased milk α‐tocopherol concentration by 86 and 134% at low and high altitude (P<0.001), respectively. Changes in the ruminal ecosystem due to energy shortage or specific secondary plant metabolites are discussed as possible causes for the high 18∶3n−3 concentrations in alpine milk.
Changes in the milk and cheese fat composition of ewes fed commercial supplements containing linseed with special reference to the CLA content and isomer composition
Authors: Luna Pilar , Fontecha Javier , Juárez Manuela , de la Fuente Miguel Angel
Published: November 2006

A study was carried out to increase the CLA contents in ewes’ milk fat under field conditions by dietary means and to investigate the extent of the changes and consequences for milk processing and cheese quality. During a 3‐mon period, ewes’ bulk milk samples were collected every week from two different herds. For the first 4 wk the ewes were fed a conventional diet. Then the following 6 wk a supplement enriched in α‐linolenate (whole linseed) was incorporated into the ovine diet. Finally, in the last 3 wk the feeding was the same as in the first 4 wk. The FA profile in milk fat was monitored by GC, and the distribution of CLA isomers was thoroughly tested by combining GC‐MS of 4,4‐dimethyloxazoline derivatives (DMOX) with silver ion‐HPLC (Ag+‐HPLC) of FAME. Reconstructed mass spectral profiles of CLA characteristic ions from DMOX were used to identify positional isomers, and Ag+‐HPLC was used to quantify them. An increase in total CLA in milk fat was observed, and total CLA remained elevated during the weeks of enriched α‐linolenate feeding. In our experimental conditions there was a linear relationship between trans‐vaccenic acid (trans‐11‐octadecenoic acid; trans‐11 18∶1) and 9‐cis, 11‐trans CLA in ewes’ milk fat. Concerning the CLA isomer profile, increases in the 11,13‐ and 12,14–18∶2 positional isomers were considerable when linseed was included in the diet. Organoleptic characteristics of cheeses made with CLA‐enriched milk did not substantially differ from those made with nonsupplemented ewes’ milk. CLA total content and isomer profile did not change during ripening.
Effect of 18∶1n−9, 20∶5n−3, and 22∶6n−3 on lipid accumulation and secretion by atlantic salmon hepatocytes
Authors: Vegusdal A. , Gjøen T. , Berge R. K. , Thomassen M. S. , Ruyter B.
Published: November 2006

We have studied the effects of dietary FA on the accumulation and secretion of [3H]glycerolipids by salmon hepatocytes in culture. Atlantic salmon were fed diets supplemented with either 100% soybean oil (SO) or 100% fish oil (FO), and grew from an initial weight of 113±5 g to a final weight of 338 ±19 g. Hepatocytes were isolated from both dietary groups and incubated with [3H]glycerol in an FA‐free medium; a medium supplemented with 0.75 mM of one of three FA—18∶1n−9, 20∶5n−3, or 22∶6n−3—or a medium supplemented with 0.75 mM of the sulfur‐substituted FA analog tetradecylthioacetic acid (TTA), which cannot undergo β‐oxidation. Incubations were allowed to proceed for 1,2,6, or 24 h. The rate of the secretion of radioactive glycerolipids with no FA added was 36% lower from hepatocytes isolated from fish fed the FO diet than it was from hepatocytes isolated from fish fed the SO diet. Hepatocytes incubated with 18∶1n−9 secreted more [3H]TAG than when incubated with no FA, whereas hepatocytes incubated with 20∶5n−3 or TTA secreted less labeled TAG than when incubated with no FA. This observation was independent of the feeding group. Hepatocytes incubated with 22∶6n−3 secreted the highest amounts of total [3H]glycerolipids compared with the other treatments, owing to increased secretion of phospholipids and mono‐ and diacylglycerols (MDG). In contrast, the same amounts of [3H]TAG were secreted from these cells as from cells incubated in an FA‐free medium. The lipid‐lowering effect of FO is thus independent of 22∶6n−3, showing that 20∶5n−3 is the FA that is responsible for the lipid‐lowering effect. The ratio of TAG to MDG in lipids secreted from hepatocytes to which 20∶5n−3 or TTA had been added was lower than that in lipids secreted from hepatocytes incubated with 18∶1n−9 or 22∶6n−3, suggesting that the last step in TAG synthesis was inhibited. Morphometric measurements revealed that hepatocytes incubated with 20∶5n−3 accumulated significantly more cellular lipid than cells treated with 18∶1n−9, 22∶6n−3, TTA, or no treatment. The area occupied by mitochondria was also greater in these cells. The present study shows that dietary FO reduces TAG secretion from salmon hepatocytes and that 20∶5n−3 mediates this effect.
Changes in phosphatidylcholine molecular species in the shrimp Macrobrachium borellii in response to a water‐soluble fraction of petroleum
Authors: Lavarías Sabrina , Dreon Marcos S. , Pollero Ricardo J. , Heras Horacio
Published: November 2006

The effect of the water‐soluble fraction (WSF) of crude oil on lipid contents, lipid classes, FA, and PC molecular species was studied in high‐phospholipid (hepatopancreas) and low‐phospholipid (egg) tissues of a freshwater crustacean. After a 21‐d exposure to a sublethal concentration of WSF, a significant decrease in shrimp total lipids was observed, although no alterations could be detected in the hepatopancreas or egg lipid contents. TAG/phospholipid ratios increased in the hepatopancreas and decreased in the eggs, suggesting alterations either in the mobilization of TAG to phospholipid pools or in the energy balance. The FA composition of phosphoglycerides in the hepatopancreas and eggs was dominated by PUFA, whereas the n−3/n−6 ratio was not affected by WSF exposure, although there was a significant increase in hepatopancreas 18∶1n−9. Analysis of the PC molecular species by HPLC‐ELSD showed the presence of 15 species, with 16∶0/18∶1, 18∶1/18∶2, 16∶0/20∶5, and 16∶1/20∶5 being the major species in the hepatopancreas. The PC molecular species in the eggs showed a different pattern, dominated by 16∶0/18∶1 and 18∶1/18∶2. Of the PC molecular species, 10 contained 22∶6n−3, 20∶5n−3, and 20∶4n−6. Small amounts of di‐PUFA species were also found. Exposure to WSF altered the PC molecular species in both tissues. The four major hepatopancreas molecular species and most of the ones containing PUFA decreased. This was compensated for by an increase in 16∶1/18∶1 (152%) and 18∶1/18∶1 (50%). The two major egg PC molecular species decreased, whereas the PUFA‐containing ones increased. The contrasting responses of both tissues of WSF contamination suggests the presence of different homeostatic mechanisms.
Exciton-phonon coupling and disorder in the excited states of CdSe colloidal quantum dots
Authors: Salvador Mayrose R. , Graham Matthew W. , Scholes Gregory D.
Published: November 2006

We study the origin of the spectral line shape in colloidal CdSe nanocrystal quantum dots. The three-pulse photon echo peak shift (3PEPS) data reveal a temperature-independent fast decay, obscuring the quantification of the homogeneous linewidth. The optical gap and Stokes shift are found to have an anomalous behavior with temperature, which is size, capping group, and surrounding polymer matrix independent. Using these results and combining them with simulations, we discuss the role of exciton-phonon coupling, static inhomogeneity, exciton fine structure, and exciton state disorder in the linewidth of the nanocrystal. In particular, our analysis shows that the disorder due to surface imperfections and finite temperature effects, as well as the relaxation within the fine structure, can have significant impact on the steady-state absorption spectrum, 3PEPS data, and dephasing processes.
Coexistence of one- and two-dimensional supramolecular assemblies of terephthalic acid on Pd(111) due to self-limiting deprotonation
Authors: Cañas-Ventura M. E. , Klappenberger F. , Clair S. , Pons S. , Kern K. , Brune H. , Strunskus T. , Wöll Ch. , Fasel R. , Barth J. V.
Published: November 2006

The adsorption of terephthalic acid [C6H4(COOH)2, TPA] on a Pd(111) surface has been investigated by means of scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy, and near-edge x-ray absorption fine structure spectroscopy under ultrahigh vacuum conditions at room temperature. We find the coexistence of one- (1D) and two-dimensional (2D) molecular ordering. Our analysis indicates that the 1D phase consists of intact TPA chains stabilized by a dimerization of the self-complementary carboxyl groups, whereas in the 2D phase, consisting of deprotonated entities, the molecules form lateral ionic hydrogen bonds. The supramolecular growth dynamics and the resulting structures are explained by a self-limiting deprotonation process mediated by the catalytic activity of the Pd surface. Our models for the molecular ordering are supported by molecular mechanics calculations and a simulation of high resolution STM images.
Kohn-Sham perturbation theory: Simple solution to variational instability of second order correlation energy functional
Authors: Jiang Hong , Engel Eberhard
Published: November 2006

The orbital-dependent correlation energy functional resulting from second order Kohn-Sham perturbation theory leads to atomic correlation potentials with correct shell structure and asymptotic behavior. The absolute magnitude of the exact correlation potential, however, is greatly overestimated. In addition, this functional is variationally instable, which shows up for systems with nearly degenerate highest occupied and lowest unoccupied levels like Be. In this contribution we examine the simplest resummation of the Kohn-Sham perturbation series which has the potential to resolve both the inaccuracy and the instability problem of the second order expression. This resummation includes only the hole-hole terms of the Epstein-Nesbet series of diagrams, which has the advantage that the resulting functional is computationally as efficient as the pure second order expression. The hole-hole Epstein-Nesbet functional is tested for a number of atoms and ions. It is found to reproduce correlation and ground state energies with an accuracy comparable to that of state-of-the-art generalized gradient approximations. The correlation potential, on the other hand, is dramatically improved compared to that obtained from generalized gradient approximations. The same applies to all quantities directly related to the potential, as, for instance, Kohn-Sham eigenvalues and excitation energies. Most importantly, however, the hole-hole Epstein-Nesbet functional turned out to be variationally stable for all neutral as well as all singly and doubly ionized atoms considered so far, including the case of Be.
The Prigogine-Defay ratio revisited
Authors: Schmelzer Jürn W. P. , Gutzow Ivan
Published: November 2006

One of the basic characteristics of the glass transition, the Prigogine-Defay ratio, connecting jumps of the thermal expansion coefficient, isothermal compressibility, and isobaric specific heat capacity in vitrification is rederived in the framework of the thermodynamics of irreversible processes employing the order-parameter concept introduced by de Donder and van Rysselberghe [Thermodynamic Theory of Affinity (Stanford University Press, Stanford, 1936)]. In our analysis, glass-forming liquids and glasses are described by only one structural order parameter. However, in contrast to previous approaches to the derivation of this ratio, the process of vitrification is treated not in terms of Simon’s simplified model [Z. Anorg. Allg. Chem. 203, 219 (1931)] as a freezing-in process proceeding at some sharp temperature, the glass transition temperature Tg, but in some finite temperature interval accounting appropriately for the nonequilibrium character of vitrifying systems in this temperature range. As the result of the theoretical analysis, we find, in particular, that the Prigogine-Defay ratio generally has to have values larger than 1 for vitrification in cooling processes. Quantitative estimates of the Prigogine-Defay ratio are given utilizing a mean-field lattice-hole model of glass-forming melts. Some further consequences are derived concerning the behavior of thermodynamic coefficients, in particular, of Young’s modulus in vitrification. The theoretical results are found to be in good agreement with experimental data.
On theoretical predictions of noble-gas hydrides
Authors: Lignell Antti , Khriachtchev Leonid , Lundell Jan , Tanskanen Hanna , Räsänen Markku
Published: November 2006

We discuss the present status and reliability of theoretical predictions of noble-gas hydride molecules. It is shown that the single-reference MP2 calculations can produce a rather inaccurate energy diagram for the formation of noble-gas hydrides, and this may mislead the theoretical predictions. We suggest that the computational dissociation energy of the HY precursors should always be compared with the experimental values as a checkpoint for the computational accuracy. The computational inaccuracy probably explains why some compounds that are stable with the single-reference MP2 method (HArC4H, HArC3N, and HArCN) did not appear in matrix-isolation experiments, whereas the corresponding compounds with Kr and Xe are known.
IR plus vacuum ultraviolet spectroscopy of neutral and ionic organic acid monomers and clusters: Propanoic acid
Authors: Hu Y. J. , Fu H. B. , Bernstein E. R.
Published: November 2006

The vibrational spectrum of molecular propanoic acid, cooled in a supersonic expansion, in the region of 2500to7500cm−1 is obtained employing infrared plus vacuum ultraviolet nonresonant ionization detected spectroscopy. The fundamental and first overtone of the CH and OH stretch modes of cold propanoic acid molecules can be identified in the spectrum. Propanoic acid neutral and ionic clusters are also studied employing nonresonant ion dip and photodissociation spectroscopic techniques, respectively. For the neutral dimer, a sequence of features observed at ca. 2500–2700cm−1 can be assigned as combination bands of low frequency modes with the COH bending overtone; these features characterize the cyclic dimer ring structure. IR spectra of the larger neutral clusters n=3, 4, 5 indicate that they also have cyclic structures in which the OH groups are engaged in the cluster hydrogen bonding network. The CH groups are not involved in this hydrogen bonding structure. Free OH features are observed for the protonated ion clusters (C2H5COOH)nH+, n=1,…,5, indicating that at least one OH group of these cluster ions is not involved in the cluster hydrogen bonding network. A comparison of the results for four hydrogen bonding neutral and ionic clusters (CH3OH, C2H5OH, CH3COOH, and C2H5COOH) is presented and discussed.
Local polymer dynamics under strong connectivity constraints: The dendrimer case
Authors: Karatasos K. , Lyulin A. V.
Published: November 2006

The characteristics of local motion are explored by molecular dynamics simulations in a series of AB2-type dendrimer melts. Systems of generations 3–5 were simulated in a wide temperature range, allowing the assessment of effects associated with molecular size, proximity to the detected glasslike transitions, and the strong connectivity constraints imposed by the dendritic topology. Investigation of the mechanisms involved in local motion at short temporal and spatial scales revealed the connection between the non-Gaussian nature of monomer displacements to α-relaxation and the caging/decaging process under different degrees of confinement. In the latter mechanism, two characteristic localization lengths were identified: at the low temperature limit spatial localization was realized within approximately 10% of the nearest neighbor distance while at temperatures higher than the glass transition, the existence of an analogous length scale is ascribed to the geometric constraints due to the dense connectivity pattern. As the results from this study are discussed in comparison to the behavior observed in linear polymers and supercooled liquids, new insight is provided on the universal/specific mechanisms involved in local dynamics of different glass-forming systems.
Oxygen-assisted control of surface morphology in nonepitaxial sputter growth of Ag
Authors: Riveiro J. M. , Normile P. S. , Andrés J. P. , González J. A. , De Toro J. A. , Muñoz T. , Muñiz P.
Published: November 2006

The surface roughness of Ag films (thickness of 50nm) is drastically reduced from 2.4to1.0nm by the presence of oxygen (pressure of 2×10−5mbar) during sputter growth, without a change (undermining) in electrical transport properties nor a formation of any Ag oxide phase. It is concluded that oxygen plays the role of a surfactant. The growth scenario (nonepitaxial sputter deposition of relatively thick films) makes this observation complementary to previous studies reporting surfactant effects in epitaxial growth of Ag. The authors consider an application of this finding in the field of multilayers involving Ag metals.
Liquid-liquid transition in supercooled water investigated by interaction with LiCl and Xe
Authors: Souda Ryutaro
Published: November 2006

The hypothesis that supercooled water consists of two distinct liquid phases has been explored on the basis of their ability to hydrate nonpolar (Xe) and electrolytic (LiCl) species. Xe incorporated in the bulk of amorphous solid water survives in the deeply supercooled regime above the glass-transition temperature of 136K and is finally dehydrated at 165K, whereas LiCl dissolves only in the liquid phase appearing above 165K. The second liquid phase connects with normal water as inferred from high (poor) solubility of LiCl(Xe). This result also suggests that decoupling of translational diffusion and viscosity in the deeply supercooled regime is caused by domain structures of the two liquid phases formed during a possible liquid-liquid transition.