Search results for "Lipids"
showing 10 items of 2228 documents
HPLC in the characterisation of conformational species of linear gramicidins
1997
Abstract High-performance size-exclusion chromatography (HPSEC) has proved to be a highly simplified and rapid procedure to investigate the conformational behaviour of gramicidin A inserted in different model membrane systems (lipid dispersions, liposomes, micelles) based on the separation of double-stranded dimers and monomers present in the lipid assemblies. The HPSEC approach has been extended to the characterisation of acylated analogs of gramicidin (palmitoyl- and oleoyl-derivatives) and a series of peptide analogs where tryptophan residues were chemically modified or replaced by less polar residues (phenylalanine or naphtylalanine) lacking H-bonding ability. The Chromatographic result…
Alkylation of acidic organic compounds for gas chromatographic analysis
1973
A new alkylation method is proposed. Organic solutions of fatty acids, phenols or barbituric acids are refluxed with an alkylating reagent and solid K2CO3. The reaction mixture is injected directly into the gas chromatograph. The scope of this convenient method for quantitative and qualitative analyses is considerable as different classes of alkylating agents can be used.
Determination of sterols, oxysterols, and fatty acids of phospholipids in cells and lipoproteins: A one-sample method
1998
In addition to fatty acids, especially polyunsaturated species, cholesterol oxidizes and leads to various oxygenated derivatives, named oxysterols. They display a wide range of adverse biological properties. Monitoring oxysterols is important in the evaluation of the potential risks associated with lipid oxidation. In the present study, a quick and reliable method was developed for analysis of oxysterols, sterols, and fatty acid composition of phospholipids in the same biological sample. Total lipid extraction was determined after addition of several internal standards (epicoprostanol for sterols, 19-hydroxy-cholesterol for oxysterol and di-heptadecanoyl-phosphatidylcholine for phospholipid…
Über die Verbreitung von Flavonoiden bei pleurokarpen Laubmoosen II. Apigenin and Apigenin-7-rhamnoglucosid bei Pleurozium schreberi (Willd.) Mitt.
1980
Summary 12 species of pleurocarpous mosses have been investigated as to their content of flavonoids. Flavonoid tests on 11 species have given negative results. Only one species, Pleurozium schreberi , contains three flavonoids. They were purified by means of paper chromatography. Two of them are by chromatography, acid hydrolysis and absorption spectrum identical with apigenin and apigenin-7-rhamnoglucoside. The third flavonoid is as yet unidentified. Qualitative hydrolysis yields apigenin. The chemotaxonomic importance of the results is briefly discussed.
Amphiphilic derivatives of a polyaspartamide: their aggregation and solubilization ability
2006
Abstract The self-aggregation and solubilization capability of a series of amphiphilic copolymers obtained by derivatisation of polymeric chain of α,β-poly(N-2-hydroxyethyl)- dl -aspartamide (PHEA) with polyethylene glycols (PEG, being different molecular weight 2000 or 5000 Da, PEG2000 and PEG5000, respectively) and/or hexadecylamine alkyl chain (C16), namely PHEA–PEG2000, PHEA–PEG5000, PHEA–C16, PHEA–PEG2000–C16 and PHEA–PEG5000–C16, have been evidenced by performing systematic tensiometric and spectrophotometric studies. All measurements have been performed at 25.0 °C over a wide copolymer concentration range. The tensiometric results have shown that, for all copolymers studied, the surf…
Comperative studies with Culex pipiens egg rafts. Immunogenetic, electrophoretic and enzymatic analysis of unfertilized, compatible and incompatible …
1973
By applying immunologic, electrophoretic and enzymatic methods, extracts of different raft types of Culex pipiens were analysed. Rafts of the crosses Pa x Pa and Ha x Ha contained four common antigens, while unfertilized rafts of Pa and Ha (no antisera were prepared against them) and rafts of the crosses Og x Og, Og x Pa, and Pa x Og shared three common antigens with the remaining raft extracts. Disk-electrophoresis of raft extracts in acrylamide gel resulted in different electropherograms. Ten protein bands were common to all these raft types. The unfertilized rafts of Pa and Ha yielded three more protein bands, the crosses Pa x Ha and Ha x Pa one more, the crosses Og x Og and Pa x Og thre…
ChemInform Abstract: Enantioselective Addition of Nitromethane to α-Keto Esters Catalyzed by Copper(II)-Iminopyridine Complexes.
2008
The copper complex of a chiral iminopyridine easily prepared from (R)-(−)-fenchone and picolylamine catalyzes the enantioselective Henry (nitroaldol) reaction between nitromethane and α-keto esters. Good yields and modest to good enantioselectivities are obtained for a wide range of α-keto esters, bearing aromatic, alkyl or alkenyl groups attached to the ketone carbonyl group.
Absorption and intestinal catabolism of fatty acids in the rat: effect of chain length and unsaturation
1991
Simultaneous portal blood absorption and intestinal mucosal catabolism of labelled fatty acids were investigated. Anaesthetized adult Wistar rats were infused intraduodenally either with 90 mumol of capric (C10:0), oleic (C18:1), linoleic (C18:2) or arachidonic (C20:4) 1-14C acids or with 30 mumol of each labelled fatty acid in addition to 30 mumol of oleic acid and 30 mumol of monopalmitin. For mixed infusates, experiments were carried out with two additional long-chain fatty acids: palmitic (C16:0) and erucic (C22:1) 1-14C acids. Radioactivity was quantified in the lipids and in the catabolic products in portal blood recovered at 5 min intervals for 1 h after infusion. At the end of the e…
Role of hexagonal structure-forming lipids in diadinoxanthin and violaxanthin solubilization and de-epoxidation
2005
In this study, we have examined the influence of different lipids on the solubility of the xanthophyll cycle pigments diadinoxanthin (Ddx) and violaxanthin (Vx) and on the efficiency of Ddx and Vx de-epoxidation by the enzymes Vx de-epoxidase (VDE) from wheat and Ddx de-epoxidase (DDE) from the diatom Cyclotella meneghiniana, respectively. Our results show that the lipids MGDG and PE are able to solubilize both xanthophyll cycle pigments in an aqueous medium. Substrate solubilization is essential for de-epoxidase activity, because in the absence of MGDG or PE Ddx and Vx are present in an aggregated form, with limited accessibility for DDE and VDE. Our results also show that the hexagonal st…
Glycoside synthesis via electrophile-induced activation of N-allyl carbamates
1993
Abstract O-Benzyl-, O-acyl-, N-acyl- and isopropylidene-protected glycosyl N-allylcarbamates, obtained from anomerically unprotected monosaccharides and allyl isocyanate, are activated by an electrophile-induced cyclisation and react with hydroxyl compounds to form the corresponding glycosides.