Changes in gene body methylation predict phenotypic acclimatization of the coral Stylophora pistillata to ocean acidification.

No abstract

Analysis of Fatty Acids in Food Lipids Fatty acid compositional analysis of lipids is usually carried out by gas-liquid chromatography (GC). Lipids obtained from food samples have complex structures and often fall into the following classes: triacylglycerols, phospholipids, sphingolipids, and sterols. Sterols exist in both animal-and plant-originated foods in either a free form (e.g., free cholesterol) or esterified form (e.g., cholesterol esters). Generally, most of the fatty acids found in food lipids are covalently bound to either an alcohol (glycerol) via ester bonds (triacylglycerols, phospholipids, and sterol esters), or to a long-chain base (sphingosines) via amide bonds (sphingolipids). To analyze the fatty acid composition of food lipids, the complex lipids must be pretreated so that the individual fatty acids are available for chromatographic analysis. For this purpose, fatty acids in the complex lipids are converted to their corresponding methyl esters by various derivatization methods to make them volatile for GC analysis. Since the focus of this unit is fatty acid analysis, and fatty acids from sterol esters contribute only a small portion of the total fatty acid pool, issues typical to the analysis of sterol-bound fatty acids will not be discussed; however, it should be noted that the protocols described in this unit do not work well for fatty-acid esterified sterols. There are basically two mechanisms to convert the fatty acids in a complex lipid to fatty acid methyl esters (FAMEs): methylation following hydrolysis of the fatty acids from the complex lipids, or direct transesterification. The first mechanism involves saponification (alkaline hydrolysis) in which the ester bond is cleaved between the fatty acid and the glycerol moiety (e.g., triacylglycerols and phospholipids) under heat and in the presence of an alkali (usually sodium hydroxide), followed by methylation performed in the presence of an acidic catalyst in methanol. Direct transesterification is usually a one-step reaction involving alkaline or acidic catalysts. This unit describes two basic protocols and one alternate protocol for FAME derivatization, and one support protocol for lipid extraction. The derivatization procedures described in this unit are suitable for a small amount of sample, ranging from 2 to 50 mg, which is particularly compatible with GC analysis using today's popular capillary or megabore fused-silica columns. In the first protocol, FAMEs are prepared from lipid samples by sodium hydroxide saponification followed by boron trifluoride (BF 3)-catalyzed esterification (see Basic Protocol 1). This procedure is adopted from the official methods (AOCS, 1989; Firestone, 1995) with modification. Basic Protocol 1 is suitable for most lipid analyses. Since BF 3 and other acidic catalysts will change the conformation of conjugated dienoic fatty acids (e.g., conjugated octadecadienoic acids; conjugated linoleic acids; CLA), this method is not recommended for lipid samples having these special structures, such as dairy product...

Effects of dietary conjugated linoleic acids (CLAs) and docosahexaenoic acid (DHA) on the fatty acid composition of different egg compartments after storage were studied. Four dietary treatments [supplemented with safflower oil (SAFF, control group), DHA, CLAs plus DHA (CAD), and CLAs alone] were administered to Single Comb White Leghorn (SCWL) laying hens. Eggs from the different treatment groups were collected and stored for 10 weeks at 4 degrees C before analysis. Fatty acids from the yolk (yolk granules and plasma), egg albumen, and vitelline membrane were analyzed by gas chromatography. The yolk of eggs from hens given CLAs had significantly higher amounts of saturated fatty acids, typically 16:0 and 18:0, but lower amounts of polyunsaturated fatty acids (PUFAs) compared to eggs from the control group (SAFF). CLA content was highest in the yolk and present in both neutral and polar lipids, with the greatest concentrations in neutral lipids. DHA was incorporated mainly into yolk polar lipids. Lipids in yolk plasma and granules contained similar amounts of CLAs. The fatty acid compositions of vitelline membrane and egg albumen mirrored that of the egg yolk. CLA supplementation resulted in hard and rubbery yolks when compared to hard-cooked eggs from the control group. This study showed that feeding CLAs to hens led to accumulation of the isomers in polar and neutral lipids of the egg yolk and that these isomers migrated into egg albumen. Because the sensory properties of hard-cooked eggs were negatively affected by the enrichment of a mixture of CLA isomers in this study, further research should be conducted to evaluate how the different isomers alter the properties of egg yolk and albumen so that the quality of designed eggs containing CLAs and DHA can be improved.