Higher Concentrations Of Esters Research Articles

A comparison of the lipid compositions of the lipoproteins of the intestinal and popliteal lymph and plasma of sheep

AbstractThe lipids and lipoproteins of intestinal lymph in the sheep make a contribution to the corresponding fractions in plasma and thence affect lipid compositions in other tissues. As a first step towards assessing this contribution, the lipoproteins of intestinal lymph, peripheral (popliteal lymph) and plasma have been isolated for compositional studies. Popliteal lymph and the plasma were similar in the distributions of lipids among the major lipoprotein fractions with high‐density lipoproteins accounting for just over half of the total lipid present. In intestinal lymph, 80 per cent of the total lipid was associated with the very low‐density lipoprotein fraction. Whereas triacylglycerols comprised the principal lipid component of the very low‐density lipoprotein and low‐density lipoprotein fractions of the intestinal lymph and were present in the high‐density lipoprotein fraction, they were present in essence only in the very low‐density lipoprotein fraction of popliteal lymph and plasma, where high concentrations of cholesteryl esters and phospholipids were found in all the lipoprotein fractions. The fatty acid compositions of each lipid class were also determined. The most distinctive feature of the results was the distribution of the essential fatty acid, linoleic acid, among the lipid components. In all lipid classes in each of the body fluids, the concentration of this component was highest in the high‐density lipoproteins and lowest in the very low‐density lipoproteins. Higher concentrations tended to be present in the triacylglycerols and phosphatidylcholine fractions of intestinal lymph than of plasma and popliteal lymph, but the opposite was true of the cholesteryl esters. The results are discussed in terms of the sources of the linoleic acid in the lipids of intestinal lymph of ruminant animals.

The Neutral Lipids of Paramecium tetraurelia: Changes with Culture Age and the Detection of Steryl Esters in Ciliary Membranes1

ABSTRACTNeutral lipids, particularly triglycerides, accounted for the major decrease in the total lipid content in Paramecium cells that occurs with culture age. Sterols, triglycerides, and steryl esters were the major classes of neutral lipids in cells and isolated cilia. Free as well as high concentrations of esterified sterols were detected in purified ciliary membrane preparations. Stigmasterol and 7‐dehydrostigmasterol were the major components of both free and esterified sterols of cells and cilia; however, when cholesterol was present in the growth medium, it was desaturated to 7‐dehydrocholesterol and incorporated into cellular and ciliary lipids. Free fatty acids from cells and triglycerides from cells and cilia were low in polyunsaturated fatty acids and reflected the composition of fatty acids in the culture medium. An exception was the reduced concentration of stearate in triglycerides from whole cells. Greater than 50% of triglyceride fatty acids from cilia were saturated. The fatty acid compositions of cellular triglycerides and ciliary steryl esters did not change with culture age, but those of cellular steryl esters and ciliary triglycerides did change. In comparison with phospholipids, these neutral lipid fatty acid compositional changes were smaller. The sensitivity of these stigmasterol‐containing cells to polyene antibiotics indicated that they were killed by nystatin > filipin > amphotericin B. The unexpected finding of high concentrations of steryl esters in ciliary membrane preparations is discussed.

Catalysis and inhibition of the alkaline hydrolysis of benzocaine and analogs by a cationic surfactant.

The first-order rate constants for the alkaline hydrolysis of ethyl benzoate and ethyl p-nitro- and p-aminobenzoates (benzocaine), catalyzed by CTAB, a cationic surfactant, were measured at 25°in the presence of sodium hydroxide and sodium bromide. Although the alkaline hydrolysis of esters is generally accelerated by cationic micelles, that of the three benzoates tended to be inhibited by CTAB micelles under the following conditions : (i) at high CTAB concentrations, (ii) at high concentrations of sodium hydroxide, (iii) at high concentrations of an added salt (including buffer components), (iv) at high ester concentrations, and (v) for compounds possessing a small value of the Hammett substituent constant. These effects were explained quantitatively on the basis of a theory in which the total counterion concentration is assumed to remain constant regardless of the concentrations of CTAB, sodium bromide, and sodium hydroxide, and in which the association constant for a CTAB micelle and an ester, the degree of counterion binding to CTAB micelles, the ion-exchange constant, and a relative rate constant are taken as parameters.

Effects of phthalate esters on glucose 6-phosphate dehydrogenase and other enzymes in vitro

Phthalate esters were found to inhibit purified yeast glucose 6-phosphate dehydrogenase (EC 1.1.1.49) but the crude rat liver enzyme was not inhibited. At a concentration of 0.33 μg of enzyme/ml, the concentration of dioctyl phthalate (DOP) that exhibited 50% inhibition was 15.1 μ m. Bovine serum albumin, NADP +, and NADH prevent the enzyme from the inhibition. Bovine serum albumin (2 μg/ml) completely prevented inhibition by 8.5 × 10 −5 m DOP. The inhibition strength depended on the carbon number of the alkyl groups of phthalate esters; the longer the chains of alkyl groups of phthalate esters, the more potent the inhibition. As chain length increased, the n value in modified Hill plots decreased from 4 to 2. Of 13 enzymes tested, only one enzyme was inhibited by low concentrations of phthalate esters and seven enzymes were inhibited by relatively high concentrations of phthalate esters. Pig heart malate dehydrogenase was found to be sensitive to phthalate esters, as was yeast glucose 6-phosphate dehydrogenase.

The Origin of Petrel Stomach Oils: A Review

burrow nesters, thereby possibly serving as a defense mechanism for the former. Because the oil floats on top of the stomach contents it is ejected most frequently but solid and partly-digested food may follow it. Early analyses of stomach oil from Sooty Shearwaters (Puffinus griseus; Smith 1911, Carter 1921, Carter and Malcolm 1927) and from a Fulmar (Fulmarus glacialis; Rosenheim and Webster 1927) revealed high concentrations of wax esters. In these lipids the fatty acids are esterified with long-chain alcohols, whereas in typical fats (triglycerides) they are esterified with glycerol. Because wax esters were then virtually unknown in marine animals, though known to occur in large quantities in Sperm Whales (Physeter macrocephalus; Smith 1911, Carter 1921), hypotheses were put forward to explain their origin. Carter and Malcolm (1927) considered that they might be indigestible residues from food but failed to find them in an analysis of fish and shell-fish fats (littoral and epipelagic species). They and Rosenheim and Webster (1927) independently made similar hypotheses, based on similar reasoning: the stomach oils might be secretions of the birds themselves, similar to preen gland wax but possibly originating near the nasal cavity (Rosenheim and Webster 1927), or actual preen gland wax accidentally ingested (Carter and Malcolm 1927). Matthews (1949) found evidence suggesting that the proventriculus could be the site of secretion but he emphasized that proof of a secretory origin was still required. No such proof appears to have been published but, until very recently, some ornithologists have given unwarranted credence to this hypothesis (see Ashmole 1971). A number of biochemical studies (table 1) have now revealed that petrel stomach oils are not uniform: wax esters, triglycerides and glyceryl ethers have variously been found to be the predominant lipids, and proportions have varied widely even among samples taken from the same species at the same time. It was mainly this variability that cast doubt on the secretion hypothesis (Lewis 1969), for it seemed unlikely that a secretory mechanism would vary its product so much. The hypothesis, first advanced by Hagerup (1926), of a dietary origin for the oils seemed more likely. Kritzler's (1948) experiment with a captive fulmar, which regurgitated oil resembling pork fat after being fed fatty pork (but no biochemical tests were made) tended to support this hypothesis. On the basis of their studies of petrel stomach oils, Lewis (1969) and Cheah and Hansen (1970 a,b) independently concluded that the oils were not secretions but derivatives of the diet.

Ethanol, Ethyl Esters, and Volatile Fatty Acids in Fruity Cheddar Cheese

Analyses of commercial Cheddar cheese for ethanol and ethyl esters support the postulate that the compounds principally responsible for the fruity flavor defect are ethyl butyrate and ethyl hexanoate. High ester concentrations tended to be associated with high concentrations of ethanol. Volatile free fatty acids (C2, C4, C6, and total C2–C10) were present at higher levels in normal cheese than in fruity cheese.

Esterase Activities in the Zymogen Moiety of the Streptokinase-Plasminogen Complex

Abstract It was shown earlier that streptokinase and human plasminogen form a stoichiometric complex in which the presence of a functional active center can be detected in the zymogen moiety before its proteolytic conversion to plasmin. This center was shown to react with the active site titrant pnitrophenyl-p'-guanidinobenzoate, and to possess activator activity for human plasminogen. We now show that the zymogen moiety of the complex is capable of hydrolyzing lysine and acetyllysine methyl ester, as well as tosylarginine methyl ester, at rates approximately one-half that of the fully developed streptokinase-plasmin complex. At sufficiently high ester concentrations, activation to streptokinaseplasmin can be completely arrested, as the esters compete with plasminogen for the activator center in the streptokinaseplasminogen complex. This inhibition prolongs the life of this transient active complex, and has permitted in this study the determination of kinetic constants for acetyllysine methyl ester hydrolysis, as well as the quantitative determination of the relative activator activities of streptokinaseplasminogen and streptokinase-plasmin. The effects of bovine pancreatic trypsin inhibitor and of soybean trypsin inhibitor were also determined on the esterase activity of plasmin and its streptokinase complexes. Finally, a recent suggestion, that it is the streptokinase moiety of the activator complex which bears the active center, was examined by active site titration: no evidence was found to support this hypothesis.

Fractional vacuum distillation of herring oil methyl esters

AbstractMethyl esters of a Canadian Atlantic herring oil containing 62% monoethylenic fatty acids were subjected to batch fractional distillation under vacuum on a pilot plant scale, to study the feasibility of fractionating fatty acid esters of marine oils of low iodine value into monounsaturated fractions with increased commercial value for industrial chemical uses. A total of 64 methyl ester fractions were collected and analyzed by gas liquid chromatography. Recoveries of the major saturated and monounsaturated acids were close to 100%, and some fractions contained over 90% of the desired 22:1 long chain monounsaturated acids. The short chain polyunsaturated acids were recovered in good yields, but the long chain highly unsaturated acids were recovered in yields of 60% or less due to oxidative and thermal decomposition in the particular apparatus employed. If small amounts of unsaturated acids are acceptable, fractional distillation of low iodine value marine oils could inexpensively supply fractions with high concentrations of methyl esters of longer chain (C20 and C22) monounsaturated and shorter chain (C14) saturated acid or (C16) saturated‐monounsaturated acid mixture.

An examination of the volatile compounds present in cooked bramley's seedling apples and the changes they undergo on processing

AbstractAn efficient, yet relatively inexpensive combined gas chromatography‐mass spectrometry‐odour port unit has been used to follow the changes in the volatiles of cooking apples during cooking. Since headspace samples contained insufficient volatiles for mass spectrometric identification, they were isolated by a Likens and Nickerson extractor, the pentane extract being concentrated before examination. The volatiles were collected during successive intervals from the same cooking sample. Alcohols were prominent throughout the exaggerated cooking time of 6.5 h and were accompanied by varying amounts of hexanal, phenylacetaldehyde, damascenone and farnesenes. In the early stages, several esters were present in amounts sufficient for identification, but no evidence of their later evolution and of the accompanying apple odours was obtained. 2‐Furfural, benzaldehyde. 5‐methyl‐2‐furfural and 2,4‐decadienal were not detected initially, but contributed increasingly later, 2‐furfural finally becoming the predominant volatile.A taste panel established a highly significant difference between cooked apple prepared fresh from Bramley's stored at +5 °C for 5 months and blast‐frozen precooked apple, stored for 5 months at −20 °C and made originally from the same batch of Bramley's. The former was preferred as being less acid and having more apple flavour. Instrumental comparison of extracts prepared by the above methods showed that precooked frozen apple stored for only 1 week contains relatively higher concentrations of esters and of n‐hexanal than after 5‐months' storage, when traces of the decadienal were found. The sensory and instrumental evaluations thus accord with one another.

Nutrition of the Almond Moth. I. Analysis and Improvements of the Experimental Diet12

Cadra cautella (Walker) larvae, were reared on a modification of Fraenkel and Blewett’s diet, and the effect of the diet components on larval growth and survival was studied. Casein and sucrose in a ratio of 1:1 was a satisfactory protein-carbohyrate combination. Larval growth retardation and/or high mortality were caused when thiamin, riboflavin, pyridoxine, Ca pantothenate, folic acid, biotin, and nicotinic acid were individually omitted from the diet. No significant effect was found when p -aminobenzoic acid, choline, inositol, and vitamin B12 were individually reduced in the diet or omitted. When cholesterol was in the diet, wheat germ oil could be replaced by an unsaturated fatty acid. Without the fatty acid or wheat germ oil only a small number of larvae reached pupation, and fewer emerged. Linolenic acid was more effective than linoleic acid. The highest concentrations of esters of both acids were detrimental to larvae; linolenate was less detrimental in the lower concentrations. No pupation occurred when sterol was omitted from the diet. Fortification of the diet with K3PO4enhanced larval growth.

Phase equilibria and countercurrent distribution

AbstractTernary diagrams for methyl oleate/hexane/acetonitrile and methyl palmitate/hexane/acetonitrile systems were constructed from equilibria data obtained at 20.0 and 30.4C. The diagrams varied significantly with temperature; both systems showed expanded regions of immiscibility at the lower temperature. Both the partition coefficient of the methyl ester and the mutual solubility of hexane and acetonitrile, at each temperature, varied with ester concentration in the system. At high ester concentration, an inversion of the phases was observed. The countercurrent distribution of these compounds, as influenced by these effects, is discussed.

Volatiles from Delicious Apple Essence—Extraction Methods

SUMMARY—The organic volatiles in commercial Delicious apple essence were extracted and reduced to an oil by five different extractants: isopentane, diethyl ether, charcoal (with elution by ether), liquid carbon dioxide, and 1,2‐dichloro‐1,1,2,2‐tetrafluoroethane. Identification and quantitative estimation of the maior constituents were made by gas‐liquid chromatography and mass spectrometry. Isopentane and the fluorocarbon were similar in action. Compared with ether they gave lower recoveries, especially for the low‐molecular‐weight alcohols, but they gave extracts with higher concentrations of esters and aldehydes and thus are useful for further composition studies. Liquid carbon dioxide gave an extract similar to that given by ether.Adsorption on charcoal gave generally good recoveries and was outstanding for alcohols. Panel tests indicated that the low‐molecular‐weight alcohols have only minor importance, if any, to apple aroma. A major proportion of the principal aroma‐bearing constituents was extracted by the methods used.

Radiation‐initiated copolymerization of styrene with unsaturated esters

AbstractThe kinetics of the γ‐ray‐initiated, gel‐forming copolymerization of styrene with the unsaturated ester containing 1.5 double bonds per molecule of number‐average molecular weight of 890 (derived from maleic anhydride, phthalic anhydride, and propylene glycol) have been studied with initial ester concentrations ranging from 65% to 2.4%. From experimentally determined gel fractions, rates of disappearance of styrene and ester unsaturation (measured up to complete conversion of ester unsaturation), and the degree of polymerization of the growing chains, a model is suggested based on a free radical copolymerization, assuming a single effective propagation and termination rate constant (kp and kt, respectively), and bimolecular chain termination except between a pair of immobile gel radicals. Three ester concentration ranges were considered. At high ester concentrations (≥ 50%), styrene and ester enter the gel at a constant rate (molar ratio of styrene:ester double bond of 2:1), precluding application of conventional copolymer composition theory. The rate at which overall unsaturation, α, disappears, is given by dα/dt = (kp2/kt)M2° where M2° is the initial molar concentration of ester unsaturation. The rate at which styrene, α1, disappears is given by dα1/dt = 2/3(kp2/kt)M2°(M1° + M2°)/M1°. The rate at which styrene is consumed in the dilute esterstyrene solutions (⩽4.6%), where M2° is negligibly small, is given by dα1/dt = kp(k1/2kt)1/2. Polymerization rates of the intermediate ester concentration ranges (10% to 30%) are higher than predicted from the simple model. An empirical rate expression is presented which describes these systems to 40% conversion of styrene: dα1/dt = (kp2/kt)M2° {[(1 + m)(r1 + M)]/(r1 + 2M)}, where M is the ratio of ester unsaturation to styrene in the starting mixture and r1 is the reactivity ratio for styrene, defined in the usual manner. For initial conversions of ester unsaturation (to 10%) dα/dt = (kp2/kt)M2°.