Structural study of BSA/poly(ethylene glycol) lipid conjugate complexes

In this work we report the structural characteristics of bovine serum albumin/poly(ethylene glycol) lipid conjugate (BSA/PEG(2000)-PE) complexes under physiological conditions (37 degrees C and pH 7.4) for particular fractions of BSA to PEG-lipid concentration, CBSA/C-PEG2000-PE. Ultraviolet fluorescence spectroscopy (UV) results shown that PEG(2000)-PE is associated to BSA, leading to;protein unfolding for fixed C-BSA = 0.01 wt % and variable C-PEG2000-PE = 0.0015-0.6 wt %. Tryptophan groups on the BSA surface are in contact with the PEG-lipid at C-PEG2000-PE = 0.0015 wt %, while they are exposed to water at C-PEG2000-PE (>)0.0015 wt %. Dynamic and static light scattering (DLS and SLS) and small-angle neutron scattering (SANS) point out the existence of individual BSAIPEG-lipid complexes in the system for fixed C-BSA = 1 wt % and variable C-PEG2000-PE = 0.15-2 wt %. DLS shows that there is only one BSA molecule per protein/PEG-lipid complex, while SLS shows that the PEG-lipid associates to the BSA without promoting aggregation between adjacent protein/ polymer-lipid conjugate complexes. SANS was used to show that BSA/PEG(2000)-PE complexes adopt an oblate ellipsoidal shape. Partially unfolded BSA is contained in the core of the oblate ellipsoid, which is surrounded by an external shell containing the PEG(2000)-PE.

Pervaporation dehydration of isopropyl alcohol with NaY zeolite incorvorated hybrid membranes

With a solution technique, NaY zeolite incorporated, tetraethylorthosilicate-crosslinked poly(vinyl alcohol) membranes were prepared. The resulting membranes were tested for their ability to separate isopropyl alcohol/water mixtures by pervaporation in the temperature range of 30-50 degrees C. The effects of the zeolite content and feed composition on the pervaporation performance of the membranes were investigated. The experimental results demonstrated that both flux and selectivity increased simultaneously with increasing zeolite content in the membranes. This was explained on the basis of the enhancement of hydrophilicity, selective adsorption, and establishment of a molecular sieving action attributed to the creation of pores in the membrane matrix. The membrane containing 15 mass % zeolite exhibited the highest separation selectivity of 3991 with a flux of 5.39 X 10(-2) kg/m(2) h with 10 mass % water in the feed at 30 degrees C. The total flux and flux of water were close to each other for almost all the studied membranes, and this suggested that the membranes could be used effectively to break the azeotropic point of water/isopropyl alcohol mixtures to remove a small amount of water from isopropyl alcohol. From the temperature-dependent diffusion and permeation values, the Arrhenius activation parameters were estimated. The activation energy values obtained for water were significantly lower than those for isopropyl alcohol, and this suggested that the developed membranes had a higher separation efficiency for water/isopropyl alcohol systems. The activation energy values for total permeation and water permeation were found to be almost the same for all the membranes, and this signified that coupled transport was minimal because of the highly selective nature of the membranes. Positive heat of sorption values were observed in all the membranes, and this suggested that Henry's mode of sorption was predominant. (c) 2008 Wiley Periodicals, lnc.

Microblock ionomers: a new concept in high temperature, swelling-resistant membranes for PEM fuel cells

A novel series of polyaromatic ionomers with similar equivalent weights but very different sulphonic acid distributions along the ionomer backbone has been designed and prepared. By synthetically organising the sequence-distribution so that it consists of fully defined ionic segments (containing singlets, doublets or quadruplets of sulphonic acid groups) alternating strictly with equally well-defined nonionic spacer segments, a new class of polymers which may be described as microblock ionomers has been developed. These materials exhibit very different properties and morphologies from analogous randomly substituted systems. Progressively extending the nonionic spacer length in the repeat unit (maintaining a constant equivalent weight by increasing the degree of sulphonation. of the ionic segment) leads to an increasing degree of nanophase separation between hydrophilic and hydrophobic domains in these materials. Membranes cast from ionomers with the more highly phase-separated morphologies show significantly higher onset temperatures for uncontrolled swelling in water. This new type of ionomer design has enabled the fabrication of swelling-resistant hydrocarbon membranes, suitable for fuel cell operation, with very much higher ion exchange capacities (>2 meq g(-1)) than those previously reported in the literature. When tested in a fuel cell at high temperature (120 degrees C) and low relative humidity (35% RH), the best microblock membrane matched the performance of Nafion 112. Moreover, comparative low load cycle testing of membrane -electrode assemblies suggests that the durability of the new membranes under conditions of high temperature and low relative humidity is superior to that of conventional perfluorinated materials.

Ion-conducting polymers and membranes comprising them

An ion-conducting polymer wherein at least 80% of the repeat units comprise an ion-conducting region and a spacer region is disclosed. The ion-conducting region has an aromatic backbone of one or more aromatic groups, wherein at least one ion-conducting functional group is attached to each aromatic group. The spacer region has an aromatic backbone of at least four aromatic groups, wherein no ion-conducting functional groups are attached to the aromatic backbone. The polymer is suitable for use as a fuel cell membrane, and can be incorporated into membrane electrode assemblies.

The Nutritional Significance of Lipid Rafts

The structure, size, stability, and functionality of lipid rafts are still in debate, but recent techniques allowing direct visualization have characterized them in a wide range of cell types. Lipid rafts are potentially modifiable by diet, particularly (but not exclusively) by dietary fatty acids. However, it is not clear whether dietary polyunsaturated fatty acids (PUFAs) are incorporated into raft lipids or whether their low affinity to cholesterol disallows this and causes phase separation from rafts and displacement of raft proteins. This review examines the potential for dietary modification of raft structure and function in the immune system, brain and retinal tissue, the gut, and in cancer cells. Although there is increasing evidence to suggest that membrane microdomains, and their modulation, have an impact in health and disease, it is too early to judge whether modulation of lipid rafts is responsible for the immunomodulatory effects of n-3 PUFA. In addition to dietary fatty acids, gangliosides and cholesterol may also modulate microdomains in a number of tissues, and recent work has highlighted sphingolipids in membrane microdomains as potential targets for inhibition of tumor growth by n-3 PUFA. The roles of fatty acids and gangliosides in cognitive development, age-related cognitive decline, psychiatric disorders, and Alzheimer's disease are poorly understood and require clarification, particularly with respect to the contribution of lipid rafts. The roles of lipid rafts in cancer, in microbial pathogenesis, and in insulin resistance are only just emerging, but compelling evidence indicates the growing importance of membrane microdomains in health and disease.

Fatty acids as gatekeepers of immune cell regulation

Fatty acids have diverse roles in all cells. They are important as a source of energy, as structural components of cell membranes, as signalling molecules and as precursors for the synthesis of eicosanoids. Recent research has suggested that the organization of fatty acids into distinct cellular pools has a particularly important role in cells of the immune system and that forms of lipid trafficking exist, which are as yet poorly understood. This Review examines the nature and regulation of cellular lipid pools in the immune system, their delivery of fatty acids or fatty acid derivatives to specific locations and their potential role in health and disease.

Effects of dairy products naturally enriched with cis-9,trans-11 conjugated linoleic acid on the blood lipid profile in healthy middle-aged men

Background: Interest in the development of dairy products naturally enriched in conjugated linoleic acid (CLA) exists. However, feeding regimens that enhance the CLA content of milk also increase concentrations of trans-18:1 fatty acids. The implications for human health are not yet known. Objective: This study investigated the effects of consuming dairy products naturally enriched in cis-9,trans-11 CLA (and trans-11 18:1) on the blood lipid profile, the atherogenicity of LDL, and markers of inflammation and insulin resistance in healthy middle-aged men. Design: Healthy middle-aged men (n = 32) consumed ultra-heat-treated milk, butter, and cheese that provided 0.151 g/d (control) or 1.421 g/d (modified) cis-9,trans-11 CLA for 6 wk. This was followed by a 7-wk washout and a crossover to the other treatment. Results: Consumption of dairy products enriched with cis-9,trans-11 CLA and trans-11 18:1 did not significantly affect body weight, inflammatory markers, insulin, glucose, triacylglycerols, or total, LDL, and HDL cholesterol but resulted in a small increase in the ratio of LDL to HDL cholesterol. The modified dairy products changed LDL fatty acid composition but had no significant effect on LDL particle size or the susceptibility of LDL to oxidation. Overall, increased consumption of full-fat dairy products and naturally derived trans fatty acids did not cause significant changes in cardiovascular disease risk variables, as may be expected on the basis of current health recommendations. Conclusion: Dairy products naturally enriched with cis-9,trans-11 CLA and trans-11 18: 1 do not appear to have a significant effect on the blood lipid profile.

Effects of consumption of probiotics and prebiotics on serum lipid levels in humans

The objective of this article is to review existing studies concerning the effects of probiotics and prebiotics on serum cholesterol concentrations, with particular attention on the possible mechanisms of their action. Although not without exception, results from animal and human studies suggest a moderate cholesterol-lowering action of dairy products fermented with appropriate strain(s) of lactic acid bacteria and bifidobacteria. Mechanistically, probiotic bacteria ferment food-derived indigestible carbohydrates to produce short-chain fatty acids in the gut, which can then cause a decrease in the systemic levels of blood lipids by inhibiting hepatic cholesterol synthesis and/or redistributing cholesterol from plasma to the liver. Furthermore, some bacteria may interfere with cholesterol absorption from the gut by deconjugating bile salts and therefore affecting the metabolism of cholesterol, or by directly assimilating cholesterol. For prebiotic substances, the majority of studies have been done with the fructooligosaccharides inulin and oligofructose, and although convincing lipid-lowering effects have been observed in animals, high dose levels had to be used. Reports in humans are few in number. In studies conducted in normal-lipidemic subjects, two reported no effect of inulin or oligofructose on serum lipids, whereas two others reported a significant reduction in serum triglycerides (19 and 27%, respectively) with more modest changes in serum total and LDL cholesterol. At present, data suggest that in hyperlipidemic subjects, any effects that do occur result primarily in reductions in cholesterol, whereas in normal lipidemic subjects, effects on serum triglycerides are the dominant feature.

Polymorphisms in the apolipoprotein L1 gene and their effects on blood lipid and glucose levels in middle age males

Apolipoprotein L1 in plasma is associated with high- density lipoprotein. Novel APOL1 polymorphisms are investigated along with the association of two common haplotypes (Lys166Glu, Ile244Met, Lys271Arg) with circulating lipid and glucose levels. Although the amino acid substitutions occur in the amphipathic alpha helices region involved in lipid binding, these substitutions were found not to independently account for variability in circulating lipid and glucose levels in 149 middle age males.

Effects of lipid emulsions on lipid body formation and eicosanoid production by human peripheral blood mononuclear and polymorphonuclear cells

Background & aims: This study investigated the influence of four commercial lipid emulsions, Ivelip, ClinOleic, Omegaven and SMOFlipid (R), on lipid body formation, fatty acid composition and eicosanoid production by cultured human peripheral blood polymorphonuclear cells (PMN) and mononuclear cells (PBMC). Methods: PMN and PBMC were exposed to emulsions at concentrations ranging from 0.01 to 0.04%. Lipid body formation was assessed by microscopy, fatty acid composition by gas chromatography and eicosanoids by ELISA. Results: Stimulation of inflammatory cells and exposure to lipid emulsions promoted the formation of lipid bodies, but there did not appear to be differential effects of the emulsions tested. In contrast, there were differential effects of lipid emulsions on eicosanoid formation, particularly with regards to LTB4 production by PMN. Omegaven dramatically increased production of eicosanoids compared with the other emulsions in a dose-dependent manner. This effect was associated with a significantly higher level of lipid peroxides in the supernatants of cells exposed to Omegaven. Conclusions: Stimulation of inflammatory cells and exposure to lipid emulsions promotes lipid body formation and eicosanoid production, although the differential effects of different emulsions appear to be largely due to lipid peroxidation of unsaturated fatty acids in some emulsions in this in vitro system. (C) 2009 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

Nutrient gene interactions in lipid metabolism

Purpose of review To summarize recent findings relating to the impact of dietary fat composition on whole body lipid metabolism, and common gene variants on the blood lipid response to dietary fat change. Recent findings In recent years a more comprehensive understanding of the impact of polyunsaturated fat (PUFA) intake on the regulation of transcription factors involved in lipogenesis and fatty acid and lipoprotein metabolism has emerged. The evidence is suggestive of a greater potency of the long chain n-3 PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and in particular their oxidative products, relative to n-6 Pi In the area of nutrigenetics a number of common gene variants have been identified which may be important determinants of the blood lipid response to altered dietary fat composition. However, confirmation of associations in independent cohorts, and an understanding of the size effect of individual or combinations of genotypes, is often lacking. Summary Although in the future, genotyping holds the potential as a public health tool to target and personalize dietary advice, nutrigenetics is a relatively new science, and further research is needed to address the existing inconsistencies and knowledge gaps.

Age-related increases in circulating inflammatory markers in men are independent of BMI, blood pressure and blood lipid concentrations

Objective: To examine whether age-related increase in concentrations of circulating inflammatory mediators is due to concurrent increases in cardiovascular risk factors or is independent of these. Methods and results: Cytokines (IL-6, IL-18), chemokines (6Ckine, MCP-1, IP-10), soluble adhesion molecules (sICAM-1, sVCAM-1, sE-selectin) and adipokines (adiponectin) were measured in the plasma of healthy male subjects aged 18-84 years (n = 162). These were related to known cardiovascular risk factors (age, BMI, systolic and diastolic blood pressure, plasma total cholesterol, LDL cholesterol, HDL cholesterol and triacylglycerol concentrations) in order to identify significant associations. Plasma concentrations of sVCAM-1, sE-selectin, IL-6, IL-18, MCP-1, 6Ckine, IP-10 and adiponectin, but not sICAM-1, were significantly positively correlated with age, as well as with several other cardiovascular risk factors. The correlations with other risk factors disappeared when age was controlled for. In contrast, the correlations with age remained significant for sVCAM-1, IL-6, MCP-1, 6Ckine and IP-10 when other cardiovascular risk factors were controlled for. Conclusions: Plasma concentrations of some inflammatory markers (sVCAM-1, IL-6, MCP-L 6Ckine, IP-10) are positively correlated with age, independent of other cardiovascular risk factors. This suggests that age-related inflammation may not be driven by recognised risk factors. (C) 2006 Elsevier Ireland Ltd. All rights reserved.

Effects of high pressure/thermal treatment on lipid oxidation in beef and chicken muscle

Lipid oxidation was studied in beef and chicken muscle after high pressure treatment (0.1-800 MPa) at different temperatures (20-70 degrees C for 20 min, prior to storage at 4 degrees C for 7 days. Pressure treatment of beef samples at room temperature led to increases in TBARS values after 7 days storage at 4 degrees C; however, the increases were more marked after treatment at pressures >= 400 MPa (at least fivefold) than after treatment at lower pressures (less than threefold). Similar results were found in those samples treated at 40 degrees C, but at 60 degrees C and 70 degrees C pressure had little additional effect on the oxidative stability of the muscle. Pressure treatments of 600 MPa and 800 MPa, at all temperatures. induced increased rates of lipid oxidation in chicken muscle, but, in general, chicken muscle was more stable than beef to pressure. and the catalytic effect of pressure was still seen at the higher temperatures of 50 degrees C, 60 degrees C and 70 degrees C. The addition of 1%, Na(2)EDTA decreased TBARS values of the beef muscle during storage and inhibited the increased rates of lipid oxidation induced by pressure. The inhibition by vitamin E (0.05% w/w) and BHT (0.02% w/w), either alone or in combination, were less marked than seen with Na(2)EDTA, suggesting that transition metal ions released from insoluble complexes are of major importance in catalysing lipid oxidation in pressure-treated muscle foods. (c) 2007 Elsevier Ltd. All rights reserved.

Dietary, physiological, genetic and pathological influences on postprandial lipid metabolism

Most of diurnal time is spent in a postprandial state due to successive meal intakes during the day. As long as the meals contain enough fat, a transient increase in triacylglycerolaemia and a change in lipoprotein pattern occurs. The extent and kinetics of such postprandial changes are highly variable and are modulated by numerous factors. This review focuses on factors affecting postprandial lipoprotein metabolism and genes, their variability and their relationship with intermediate phenotypes and risk of CHD. Postprandial lipoprotein metabolism is modulated by background dietary pattern as well as meal composition (fat amount and type, carbohydrate, protein, fibre, alcohol) and several lifestyle conditions (physical activity, tobacco use), physiological factors (age, gender, menopausal status) and pathological conditions (obesity, insulin resistance, diabetes mellitus). The roles of many genes have been explored in order to establish the possible implications of their variability in lipid metabolism and CHD risk. The postprandial lipid response has been shown to be modified by polymorphisms within the genes for apo A-I, A-IV, AN, E, B, C-I and C-III, lipoprotein lipase, hepatic lipase, fatty acid binding and transport proteins, microsomal trigyceride transfer protein and scavenger receptor class B type I. Overall, the variability in postprandial response is important and complex, and the interactions between nutrients or dietary or meal compositions and gene variants need further investigation. The extent of present knowledge and needs for future studies are discussed in light of ongoing developments in nutrigenetics.