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F Couderc

Publications and source records attributed to F Couderc.

97 records · Page 6Linked to original sources
PubMed1991

Gas chromatography-mass spectrometry and gas chromatography-tandem mass spectrometry of cyclic fatty acid monomers isolated from heated fats.

The analysis of hydrogenated cyclic fatty acid monomers isolated from heated linseed and sunflower oils is achieved by gas chromatography-tandem mass spectrometry of their pentafluorobenzyl esters. Collisionally activated dissociation of the carboxylate anions produced by electron-capture ionization shows remote charge-site fragmentation that allows location of cyclopentane and cyclohexane rings by examining the resulting mass-analysed ion kinetic energy spectra. Oxidative ozonolysis of the methyl esters of the unsaturated cyclic fatty acid monomers allows location of some double bonds. However, preliminary results obtained with remote charge fragmentation of synthetic unsaturated models make this approach an alternative for double bond location in the cyclic fatty acid monomers isolated from heated fats.

Cyclopentanes↗
PubMed1991

Mass spectrometry as a tool for identifying group D2 corynebacteria by their fatty acid profiles.

Corynebacterium group D2 (CGD2) are lipophilic antibiotic-multiresistant bacteria involved in some infections of immunocompromised patients. The fatty acid composition and structure of different strains was established by several mass spectrometric methods, particularly negative ion tandem mass spectrometry coupled with capillary gas chromatography. Non-hydroxylated fatty acid profiles of three strains of CGD2 (ATCC 43042, ATCC 43043, ATCC 43044) were almost identical and revealed the presence of several straight chain unsaturated fatty acids from the omega-9 series, with even carbon numbers ranging from 14 to 24. Branched saturated fatty acids were mainly anteiso-heptadecanoic acid and tuberculostearic acid. Surprisingly, a relatively large quantity of 10-methylene octadecanoic acid was found. The non-hydroxylated fatty acid profile of one rare beta-lactam susceptible strain (SC1) was different; 10-methylene octadecanoic acid was lacking whereas tuberculostearic acid was much more abundant. In contrast, the four CGD2 strains displayed highly similar mycolic acid patterns. The major mycolic acid species corresponded to C32, C30 and C28 bis-unsaturated with a double bond on each branch at the omega-9 position. The comparison of the mycolic acid composition and structure with those of other medically important corynebacteria strains, revealed a characteristic pattern for CGD2 strains, and CGD2 strains were easily distinguished from Corynebacterium jeikeium (CIP 82.51).

Bacterial Typing Techniques↗
PubMed1989

Structure determination of mycolic acids by using charge remote fragmentation.

The collision-induced remote site fragmentation process of closed-shell ions, such as carboxylate anions, is a very potent analytical tool for the structural determination of fatty acids. This leads to an easy location of branch points, double bonds, cyclopropane rings and other functional groups. Although corynomycolic acid mixtures from Corynebacterium diphtheriae can be directly analyzed by negative-ion fast atom bombardment combined with collisionally activated decomposition spectra, mycolic acid mixtures from mycobacteria need a preliminary chemical cleavage. They are oxidized to beta-keto esters and then submitted to a retro-Claisen reaction. The resulting fatty acids were then converted into pentafluorobenzyl derivatives and introduced directly into a high pressure ion source working in the negative ion mode. The resulting gas phase carboxylate anions are activated to decompose by collision with helium atoms. When applied to M3-mycolic acids from Mycobacterium fallax, this method allows for the characterization of a new tri-unsaturated mycolic acid, which has the middle and the remote double bonds separated by two methylene groups.

Corynebacterium diphtheriae↗
PubMed1988

Analysis of fatty acids by negative ion gas chromatography/tandem mass spectrometry: structural correlations between alpha-mycolic acid chains and delta-5-monounsaturated fatty acids from Mycobacterium phlei.

The analysis of a complex mixture of monounsaturated fatty acids from mycobacterium phlei is achieved by capillary gas chromatographic separation of their pentafluorobenzyl esters, formation of gas-phase carboxylate anions by electron capture ionization and decomposition of these anions by collision activation. This method allows the structural determination of fatty acid isomers by examination of their collisionally activated dissociation mass-analysed ion kinetic energy spectra. A good correlation is observed between the structure of the unsaturated fatty acids ranging from C24 to C27 and the methyl terminal part of the main chain of diunsaturated mycolic acids.

Fatty Acids↗
PubMedDate not supplied

Quantitation of RT-PCR products of bFGF-mRNA by capillary electrophoresis and laser-induced fluorescence.

The numerous challenges of modern biology and medical science require the development of analytical methodologies of extreme sensitivity and resolving power. Because it deals with the extraordinary complexity of biological mixtures and minute samples, capillary electrophoresis combined with laser-induced fluorescence (LIF) is now one of the most popular analytical biotechniques. Using polymer matrices and very high voltages, it allows the separation of very low quantities of microsamples and the selective detection of fluorescent species at a level of a few thousand molecules. This method of analysis has been used to quantitate reverse transcription-polymerase chain reaction (RT-PCR) products. In the authors' laboratory, they were looking for a means of analyzing mRNAs of cytokines. In the first attempt, they chose to quantitate RT-PCR products of basic fibroblast growth factor (bFGF)-mRNA, which could be involved in atherosclerosis. The results on two patients confirm the lower quantity of bFGF expressed in internal mammary athery (IMA) biopsies compared to human aortic cells. This study shows the usefulness of CE-LIF to identify and quantitate RT-PCR products and its ability to be used in clinical studies, to find very low levels of bFGF expression in atheroma biopsies.

Arteries↗