Study of the corrosion of stainless steel with fatty acid/paraffin/graphite composite phase change materials

The corrosion performance of phase change materials on stainless steel was studied using single fatty acid, fatty acid/paraffin mixed phase change materials and fatty acid/paraffin/graphite composite phase change materials as corrosion media. The results show that the corrosion of fatty acid, paraffin and graphite composite phase change materials to stainless steel is very small; among them, stearic acid series of phase change materials are the least corrosive and can be used as the ideal energy storage medium for stainless steel phase change heat storage and heat exchange devices.

Determination of proximate composition and fatty acid profiles of Astacus leptodactylus Eschscholtz, 1823 in Turkish freshwater resources

This research was conducted to evaluate the nutrient content ofAstacus leptodactylusin various populations in the lakes Iznik and Egirdir, as well as in Hirfanlı Dam Lake and Keban Dam Lake, all in Turkey. Crayfish meat yield ranged from a minimum of 11.3% to a maximum of 16.3% of wet weight in specimens from Keban and Iznik, respectively. Meat yield was significantly different, depending on the living environment. The protein content of the meat ofA. leptodactylusranged from 15.4 to 17.5%. The moisture content of crayfish was significantly lower in the high lipid containing Iznik Lake’s crayfish. Crayfish lipids were poor in saturated fatty acids, but rich in PUFA’s and in particular EPA, DHA and ARA. In all groups, the major saturated fatty acids were palmitic acid, stearic acid and myristic acid. Among the omega-6 fatty acid series, a high level of ARA was observed in crayfish meat.EPA may be considered as the major omega-3 fatty acid in crayfish lipids. There was no single fatty acid indicating regional differences in crayfish specimens.

Incorporation of Exogenous Fatty Acids Protects Enterococcus faecalis from Membrane-Damaging Agents

ABSTRACTEnterococcus faecalisis a commensal bacterium of the mammalian intestine that can persist in soil and aquatic systems and can be a nosocomial pathogen to humans. It employs multiple stress adaptation strategies in order to survive such a wide range of environments. Within this study, we sought to elucidate whether membrane fatty acid composition changes are an important component for stress adaptation. We noted thatE. faecalisOG1RF was capable of changing its membrane composition depending upon growth phase and temperature. The organism also readily incorporated fatty acids from bile, serum, and medium supplemented with individual fatty acids, often dramatically changing the membrane composition such that a single fatty acid was predominant. Growth in either low levels of bile or specific individual fatty acids was found to protect the organism from membrane challenges such as high bile exposure. In particular, we observed that when grown in low levels of bile, serum, or the host-derived fatty acids oleic acid and linoleic acid,E. faecaliswas better able to survive the antibiotic daptomycin. Interestingly, the degree of membrane saturation did not appear to be important for protection from the stressors examined here; instead, it appears that a specific fatty acid or combination of fatty acids is critical for stress resistance.

Identification of phospholipase B from Dictyostelium discoideum reveals a new lipase family present in mammals, flies and nematodes, but not yeast

The social amoeba Dictyostelium discoideum exhibits high activities of phospholipase and lysophospholipase [Ferber, Munder, Fischer and Gerisch (1970) Eur. J. Biochem. 14, 253–257]. We assayed Dictyostelium lysates to demonstrate the presence of a highly active phospholipase B (PLB) enzyme that removed both fatty-acid chains from phosphatidylcholine and produced the water-soluble glycerophosphorylcholine. We purified the PLB activity from Dictyostelium cytosol using standard agarose media (size exclusion and ion exchange), and combined this with an affinity purification step using myristoylated ARF1 (ADP-ribosylation factor 1), a protein which has a single fatty acid at its N-terminus. Two proteins co-purified (48 kDa and 65 kDa), and the 48 kDa protein was digested with trypsin, peptide fragments were separated by reverse-phase chromatography, and the resultant peptides were sequenced by Edman degradation. From the peptide sequences obtained, database searches revealed a gene which encodes a protein of 65 kDa with unknown function. The 48 kDa protein therefore appears to be a fragment of the full-length 65 kDa product. Expression of the gene in Escherichia coli confirmed that it encodes a PLB. Characterization of its substrate specificity indicated that, in addition to phosphatidylcholine deacylation, the enzyme also hydrolysed phosphatidylinositol and phosphatidylethanolamine. The PLB identified in the present study is not related to existing PLBs found in bacteria, fungi or mammals. There are, however, genes similar to Dictyostelium PLB in mammals, flies, worms and Giardia, but not in yeast. We therefore have identified a novel family of intracellular PLBs.

Lipids and their seasonal variation in the nucellar layers of Scots pine (Pinus sylvestris) seeds

The content, composition, and seasonal variation of lipids in the nucellar layers of two mature Scots pine seed lots from northern and central Finland were studied. These lipophilic layers, which are located inside the seed coat, are composed of collapsed cells and restrict the imbibition of seeds. In this study, epicuticular wax was found on their surface; in particular, the surface of the nucellar cap was composed of intermeshing wax rods. The content of total lipids of the nucellar layers varied seasonally from 10 to 24%, being highest in April. In addition to simple lipids, which formed the most abundant lipid fraction in nucellar layers, small amounts of phospho- and glyco-lipids were also present. The proportion of simple lipids and their fatty acid composition in the seeds of both provenances remained constant throughout the year, whereas seasonal variation was found in the proportions of phospho- and giyco-lipids and in their fatty acids. In general, the variation was more marked in the northern seed lot. The unsaturated fatty acids dominated in the fractions of simple lipids and phospholipids, with linoleic acid being the most abundant single fatty acid. The saturated fatty acids with more than 22 carbon atoms were most abundant in the glycolipid fractions. The role of lipids for the function of the collapsed nucellar layers in the regulation of imbibition and germination of pine seeds is discussed. Keywords: Pinus sylvestris L., northern seeds, fatty acids, imbibition, germination.

Response of serum triglycerides of endogenous origin to the administration of triglyceride-rich lipid particles

Studies were performed in rats to quantitate the changes in the concentration of serum triglycerides (TGs) of endogenous and exogenous origin after the acute intravenous injection of TG-rich emulsion particles. Emulsions were prepared to approximate chylomicrons and to contain a TG with a single fatty acid that could be traced during its clearance from the serum. After injection of emulsions, there was a rapid increase of not only the emulsion TG but TGs that contained a variety of other fatty acids of endogenous origin. Endogenous TGs were cleared from the serum at a slower rate than the emulsion TG and accounted for the major increase in serum TGs, especially during the latter phase of the clearance period. The increase in endogenous TGs was completely abolished by hepatectomy, which had no effect on the clearance of the emulsion TG. Results thus show that TGs of hepatic origin accumulate in the serum in response to the introduction of new TG-rich lipoproteins. Feeding rats a specific TG produced a similar result, with a pronounced rise in endogenous TGs that, like the changes after emulsion administration, was particularly evident once the TG that was fed was largely cleared from the serum. These findings are consistent with a process in which the preferential clearance of chylomicron TGs interrupts the clearance of very low density lipoprotein TGs that are produced by the liver. Consequently, the composition of serum TGs that accumulate after a meal may not reflect the composition of the meal itself.

Interrelated lipid alterations and their influence on the proliferation and fusion of cultured myogenic cells

We have cultured myogenic cells derived from primary explants and a cell line (L6) in a lipid-depleted medium (LDM) and produced large alterations of the fatty acyl and polar headgroup composition and of the cellular sterol levels. These alterations were produced by altering the composition of the media as follows: removing biotin and providing exogenous fatty acid; removing choline and providing exogenous ethanolamine or choline analogues; and by adding 25-OH cholesterol, an inhibitor of 3-hydroxy-3-methylglutarate (HMG)-CoA reductase. Relatively small, secondary alterations of other lipid classes accompany the large primary alteration. In general, they are not obviously compensatory for the primary alteration by retaining some physical property. We have explored the influence of these lipid alterations on myoblast proliferation and fusion into myotubes. In general, considerable variability appears tolerated, but there also appear to be limits. Long-term cultures grown in media containing a single fatty acid do not proliferate indefinitely, and the fatty acid does not become the sole fatty acyl component of the phospholipids. This phenomenon is also observed for cultures enriched in phosphatidylethanolamine (PE) or phosphatidyldimethylethanolamine (PDME). The influence of the lipid alterations on fusion is particularly interesting. The inclusion of 25-OH cholesterol inhibits fusion. Enrichment of the fatty acyl chains with elaidate or the polar headgroups with PE also inhibits fusion, but in contrast to that by 25-OH cholesterol, a significant fraction of the myoblasts are aligned and interacting with each other. Oleate enrichment enhances the rate of fusion.