Fazil O. Gülaçar

Novel triterpene-derived hydrocarbons of the arborane/fernane series in sediments: Part II

Two ring-B aromatized triterpenes related to the arborane/fernane series were isolated from an Italian Triassic black shale (4 and 7) and a French Jurassic laminated bituminous limestone (7). They were identified by MS and NMR spectroscopy. These compounds, 25-norferna-5,7,9-triene 7 (C29) and 22,25,29,30-tetranor-18β-ferna-5,7,9-triene 4 (C26), in the case of the Italian sediment, belong to a family which extends to at least C32 as shown by GC-MS. The presence of higher homologs and ring-A methylated structures in the Italian Triassic shale is analogous with the hopane series, which together with carbon isotopic data obtained by gas chromatography-isotope ratio mass spectrometry (GC-IRMS), strongly support a bacterial origin for most of these compounds. This suggests that 4 and 7 may result from a yet unrecognized rearrangement of sedimentary hopenes which have subsequently undergone ring-B aromatization. As an alternative, the C29 compound 7 could arise from C30 precursors not necessarily of bacterial origin (fernenes?). This hypothesis would apply particularly to the case of the Jurassic limestone, which does not show any trace of 4 nor of compounds with an extended side chain or a methyl group on ring A. Related structures also bearing an isopropyl group could derive by microbiological transformations from the corresponding fernen-3β-ols or isoarborinol as can be deduced from the occurrence of ring-A degraded monoaromatic hydrocarbons 3 and 5.

Steroidal ketones in the early diagenetic transformations of Δ5 sterols in different types of sediments

Incubation experiments of cholesterol labelled with various isotopes (2H, 3H and 14C) were performed in two different types of sediment, one highly oxygenated and the other completely anoxic, to ascertain the presence and the role of steroidal ketones in the early diagenesis of unsaturated sterols. Two different pathways for the hydrogenation of cholesterol have been observed, depending on the oxygenation rate of the sediment. If the intermediacy of steroidal ketones is evident in the oxic sediments of Lake Leman (Switzerland), a direct reduction of the Δ5 double bond also occurs in the anoxic sediments of Motte Lake (France).

Analysis of Phenolic and Other Aromatic Compounds in Honeys by Solid-Phase Microextraction Followed by Gas Chromatography−Mass Spectrometry

The solid-phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS) was used for the analysis of phenolic and other aromatic compounds in honey samples from different floral origin. Different parameters affecting the efficiency of the extraction, such as the type of the stationary phase of the fiber, NaCl and acetic acid addition, and extraction time, were optimized for the detection of the maximum number of compounds in the shortest analysis time. A total of 31 compounds were detected, with most of them identified and quantified by GC-MS. The principal component analysis (PCA) was applied to the data matrix; the results allowed for the differentiation between honeydew and nectar honeys on the basis of the salicylic acid concentration. It was found that this acid has a high contribution in the honeydew group (71.2-705.9 microg/100 g of honey) compared to the nectar honey group (0-47.6 microg/100 g of honey). The comparison of data in each honey group enabled us to characterize the floral source of some honeys using some aromatic compounds as markers.

Molecular Characterization and Subcellular Localization of Macrophage Infectivity Potentiator, a Chlamydia trachomatis Lipoprotein

Macrophage infectivity potentiator (MIP) was originally reported to be a chlamydial lipoprotein from experiments showing incorporation of radiolabeled palmitic acid into native and recombinant MIP; inhibition of posttranslational processing of recombinant MIP by globomycin, known to inhibit signal peptidase II; and solubility of native MIP in Triton X-114. However, the detailed structural characterization of the lipid moiety on MIP has never been fully elucidated. In this study, bioinformatics and mass spectrometry analysis, as well as radiolabeling and immunochemical experiments, were conducted to further characterize MIP structure and subcellular localization. In silico analysis showed that the amino acid sequence of MIP is conserved across chlamydial species. A potential signal sequence with a contained lipobox was identified, and a recombinant C20A variant was prepared by replacing the probable lipobox cysteine with an alanine. Both incorporation of U-(14)C-esterified glycerol and [U-(14)C]palmitic acid and posttranslational processing that was inhibitable by globomycin were observed for recombinant wild-type MIP but not for the recombinant C20A MIP variant. The fatty acid contents of native and recombinant MIP were analyzed by gas chromatography-mass spectrometry, and the presence of amide-linked fatty acids in recombinant MIP was investigated by alkaline methanolysis. These results demonstrated a lipid modification in MIP similar to that of other prokaryotic lipoproteins. In addition, MIP was detected in an outer membrane preparation of Chlamydia trachomatis elementary bodies and was shown to be present at the surfaces of elementary bodies by surface biotinylation and surface immunoprecipitation experiments.

Comparison of extraction techniques for bound carboxylic acids in Recent sediments: 2. β-Hydroxyacids

Abstract Various multi-step extraction procedures were used in order to determine the β-hydroxyacid content of a Recent lacustrine sediment. Similar distribution but important quantitative differences were noted. All the β-hydroxyacids are derived from the same origin but the commonly used methanolic saponification is inappropriate for the release of bound β-hydroxyacids. All the extraction techniques produce either 3 -methoxy or 3 -chloro and Δ 2 -unsaturated carboxylic acids as artifacts from the 3 -substituted fatty acids. A two-step procedure is recommended for the extraction of the maximum amount of β-hydroxyacids with the minimum formation of artifacts.

Extraction of biomarkers from sediments with supercritical carbon dioxide : a comparative study with solvent extraction and thermodesorption methods

Supercritical fluid extraction of rocks with CO2 (SFE-CO2) can advantageously replace the organic solvent extraction technique (SE) which is generally used for the analysis of the biomarkers. The powdered rock is extracted by carbon dioxide supercritical fluid at 55°C and a pressure of 31 MPa. After decompression in a capillary restrictor, the CO2 is volatilized and the extracted compounds are trapped in hexane. An aliquot can then be directly injected into a dual GC-FID-FPD or GC-MS system. The total extraction procedure takes only 45 min and the results obtained for hopanes and steranes are in very good agreement with those of liquid solvent extraction, which requires several hours. A comparison with thermodesorption is also presented.

Lipid geochemistry of a post-glacial lacustrine sediment

Abstract The post-glacial environmental history of Voua de la Motte, a small pond, was studied by the lipid geochemistry of a 6 m long core. Palynological studies show that the deepest part of the core goes back to 10,000 yr BP corresponding to the time of formation of the lake following the retreat of the Rhodanian glacier. Hydrocarbons, aldehydes, linear alcohols, sterols, monocarboxylic and monohydroxy fatty acids, were determined throughout the core both in the free and bound lipid fractions, as well as in the tightly bound fraction for the carboxylic acids. There is no clear evidence of a transformation from the unbound to the bound form, except perhaps for the α-hydroxy acids. Qualitative as well as quantitative fluctuations in the distributions of these lipid classes were observed upward in the core. An attempt is made to correlate these fluctuations with the bioenvironmental and climatological evolution of the Basin on the basis of information obtained from palynology.

A novel sedimentary lacustrine chlorin: Characterisation and geochemical significance

We report the isolation and the characterisation by D/MS, HR-MS and 1H-NMR of a new sedimentary lacustrine chlorin with a seven membered ring. A geochemical degradation pathway is proposed on the basis of the seven membered ring resistance to degradation.

Capillary gas chromatography-mass spectrometry and identification of substituted carboxylic acids in lipids extracted from a 4000-year-old nubian burial

Polar carboxylic acid fractions of lipids extracted from samples from a 4000-year-old Nubian mummy were investigated by capillary gas chromatography mass spectrometry. They contain series of alpha,omega-dicarboxy, monohydroxy, dihydroxy and keto fatty acids, some of which were found for the first time outside the synthetic laboratory. Their chromatographic and mass spectrometric characteristic properties are reported.

Comparison of extraction techniques for bound carboxylic acids in Recent sediments: 1. Unsubstituted monocarboxylic acids

Abstract After the solvent extraction of the unbound lipids contained in a Recent lacustrine sediment, the remaining bound monocarboxylic acids were released by applying multi-step hydrolysis procedures. The relative and absolute abundances of these acids in the various hydrolysates differ greatly, thus clearly demonstrating that reliable comparisons of the fatty acid contents and distributions in various sediments require identical extraction methods. Systematic investigations show that after mild hydrolysis using either 5% KOH - methanol or 2 N HCl, the sediment still retains a large part of its fatty acids, which can be extracted after either hydrolysis in 6 N HCl or thermal treatment in 2 N KOH. The hydrolysis in HCl is much more efficient, but produces artifacts. The amounts of tightly bound fatty acids released by such treatments are important with respect to the total acid content and most of these acids are of bacterial origin. Their incomplete extraction would thus lead to greatly underestimating the microbial contribution to the sedimentary fatty acids.