The impact of choline availability on muscle lipid metabolism

Consumption of choline-rich foods is essential to ensure membrane integrity, neurotransmission and genomic methylation pathways. Insufficient dietary choline supply can cause choline deficiency (CD) which manifests in the development of non-alcoholic fatty liver disease. There is very limited information regarding the effect of CD on non-hepatic tissues such as muscle. In this study, we induced CD in muscle cells and investigated the effect on choline transport, phosphatidylcholine (PC), fatty acid and triacylglycerol (TAG, fat) metabolism. Choline transport was stable across the plasma membrane of CD cells but significantly impaired in mitochondria. The main choline-transporter SLC44A1 was down-regulated by CD at the mRNA level, and SLC44A1 protein was reduced in total cell lysates and isolated mitochondria. CD significantly reduced PC synthesis but PC degradation was unaffected. PC from CD muscle was modified and contained more monounsaturated fatty acids at the expense of saturated fatty acids. Surprisingly, CD muscle cells also accumulated TAG in the form of large lipid droplets. Those droplets were formed from endogenous fatty acids and by slower TAG metabolism. This study established for the first time that choline availability affects muscle membrane lipid composition and intracellular lipid metabolism, and underlines the significance of choline-rich foods for proper muscle function.     

Delta13C values of grasses as a novel indicator of pollution by fossil-fuel-derived greenhouse gas CO2 in urban areas

A novel fossil fuel pollution indicator based on the 13C/12C isotopic composition of plants has been designed. This bioindicator is a promising tool for future mapping of the sequestration of fossil fuel CO2 into urban vegetation. Theoretically, plants growing in fossil-fuel-CO2-contaminated areas, such as major cities, industrial centers, and highway borders, should assimilate a mixture of global atmospheric CO2 of delta13C value of -8.02 per thousand and of fossil fuel CO2 of average delta13C value of -27.28 per thousand. This isotopic difference should, thus, be recorded in plant carbon. Indeed, this study reveals that grasses growing near a major highway in Paris, France, have strikingly depleted delta13C values, averaging at -35.08 per thousand, versus rural grasses that show an average delta13C value of -30.59 per thousand. A simple mixing model was used to calculate the contributions of fossil-fuel-derived CO2 to the plant tissue. Calculation based on contaminated and noncontaminated isotopic end members shows that urban grasses assimilate up to 29.1% of fossil-fuel-CO2-derived carbon in their tissues. The 13C isotopic composition of grasses thus represents a promising new tool for the study of the impact of fossil fuel CO2 in major cities.     

Ability of whey protein isolate and/or fish gelatin to inhibit physical separation and lipid oxidation in fish oil-in-water beverage emulsion

The effect of pH on the capability of whey protein isolate (WPI) and fish gelatin (FG), alone and in conjugation, to form and stabilize fish oil-in-water emulsions was examined. Using layer-by-layer interfacial deposition technique for WPI–FG conjugate, a total of 1% protein was used to prepare 10% fish oil emulsions. The droplets size distributions and electrical charge, surface protein concentration, flow and dynamic rheological properties and physiochemical stability of emulsions were characterize at two different pH of 3.4 and 6.8 which were selected based on the ranges of citrus and milk beverages pHs, respectively. Emulsions prepared with WPI–FG conjugate had superior physiochemical stability compare to the emulsions prepared with individual proteins. Higher rate of coalescence was associated with reduction in net charge and consequent decrease of the repulsion between coated oil droplets due to the proximity of pH to the isoelectric point of proteins. The noteworthy shear thinning viscosity, as an indication of flocculation onset, was associated with whey protein stabilized fish oil emulsion prepared at pH of 3.4 and gelatin stabilized fish oil emulsion made at pH of 6.8. At pH 3.4, it appeared that lower surface charge and higher surface area of WPI stabilized emulsions promoted lipid oxidation and production of hexanal.     

β-Lactoglobulin and WPI aggregates: Formation,structure and applications

The literature is reviewed on the formation and the structure of β-lactoglobulin and whey protein isolate (WPI) aggregates in aqueous solution induced by heating. The focus is on the effects of the pH and added salt. The use of β-lactoglobulin and WPI aggregates in cold-set gels, foams and emulsions, encapsulation, and films and coatings is also reviewed.     

Osmotic Dehydration Kinetics of Pomegranate Seeds Using Date Juice as an Immersion Solution Base

Pomegranate seeds were osmodehydrated using date juice added with sucrose (final °Brix, 55) as immersion solution. The kinetics of osmotic dehydration showed that the most significant changes of mass transfer took place during the first 20 min of the process, regardless of date juice varieties. During this time, seed water loss and solid gain were estimated to be ∼39% and ∼6%, respectively. After 20 min of the process, the percentage of water loss and solid gain varied slightly and ranged on average close to ∼40% and ∼9%, respectively. During osmotic dehydration, there was a leaching of natural solutes from seeds into the solution, which is quantitatively not negligible, and might have an important impact on the sensorial and nutritional value of seeds and date juices. Both scanning electron microscopy and texture (compression) analysis revealed that osmotic dehydration process induced modifications of seed texture and cell structure. Sucrose was found to be the essential element which influences the texture of seed and the viscosity of date juice. Additionally, natural sugar present in date juice permits substituting 35% of the total quantity of sucrose added to the osmotic solution.     

In situ carburization of metallic molybdenum during catalytic reactions of carbon-containing gases

Supported molybdenum clusters were prepared by sublimation of Mo(CO)₆ onto dehy-droxylated alumina followed by decomposition in flowing dihydrogen at 970 K. These alumina-supported molybdenum clusters were found by XAFS to transform into Mo₂C if heated in a 20% methane/H₂ mixture at 950 K. For the hydrogenolysis ofn-butane at 510 K and CO-H₂ reactions at 570 K, both at atmospheric pressure, molybdenum and carburized molybdenum showed similar, but different for each reaction, turnover rates. The product distribution was the same for each reaction on Mo and Mo₂C. In both reactions, in situ XAFS data for fresh and used catalysts indicated that Mo clusters progressively transformed into Mo₂C under the reaction conditions     

Structure and functional complementation of engineered fragments from yeast phosphoglycerate kinase

Previous studies have shown that, although the isolated structuraldomains of yeast phosphoglycerate kinase recover a quasi-nativestructure in vitro as well as in vivo, they do not reassociatenor generate a functional enzyme. The aim of this work was firstto study the folding of complementary fragments different fromstructural domains and second to determine the requirementsfor their reassociation and functional complementation. Themethod used for producing rigorously defined fragments consistsof the introduction of a unique cysteinyl residue in the proteinfollowed by a specific cleavage by 5'5'-dithiobis(2-nitrobenzoate)/potassiumcyanide at this residue. Two pairs of complementary fragmentswere thus obtained, 1–96/97–415 and 1–248/249–415.The structure and stabilities of the different fragments werestudied. The short fragments, i.e. 1–96 and 249–415were found to contain some secondary structure, but to havea low stability. Each large fragment has a high structural contentand a stability close to that of the corresponding domain. Incontrast to that observed with the isolated domains, a weakbut significant complementation was observed for the two pairsof fragments; the pair of fragments 1–248/249–415recovered 8% of the activity of the native enzyme upon complementation.An independent refolding of the complementary fragments beforereassociation decreased the yield of complementation for thepair of fragments 1–96/97–415, but did not affectthe complementation for the other pair (1–248/249–415).From the present data and previous work on the isolated domains,it appears that the correct folding of the isolated fragmentsis not a prerequisite for their complementation.     

Synthesis, structure and catalytic properties of Fe-substituted barium hexaaluminates

A sol–gel method using Ba and Al isopropylates and iron nitrate has been used to synthesise barium hexaaluminate partially substituted with iron. After calcination under oxygen at 1200°C the -alumina structure was obtained. Formation of the mixed BaFe_xAl_12-xO₁₉ phase occurred for x=1–4. XRD measurements showed a good crystallinity of the structure and expansion of unit cell parameters due to the presence of larger Fe³⁺ ions substituting Al³⁺ ones in octahedral sites only. Mössbauer spectroscopy revealed that Fe³⁺ ions are present in four different octahedral sites slightly distorted. Catalytic activity in methane combustion showed that an optimum was obtained for solid containing 2 Fe ions per unit cell: the increase of the amount of introduced iron was counterbalanced by the decrease of specific surface area. Intrinsic activities have been calculated for the four solids in both the fresh and aged states. It is observed that increasing iron content increases relative activities in the same ratio as the populations of iron located in two sites as deduced from Mössbauer spectroscopy. It is then tentatively assumed that activity is attributed to octahedrally coordinated Fe³⁺ ions in some specific sites.     

Rate of adsorption to and desorption from a langmuir surface: The case of zero activation barrier to adsorption without dissociation

Many rate constants of elementary steps on single crystals have been measured. Their pre-exponential factors can now be compared to those calculated by transition state theory. Such a calculation is presented in this Letter with due attention to microscopic reversibility, standard states, and configurational entropy.