Signature GLC-MS ions in identification of Δ5- and Δ9-unsaturated iso- and anteiso-branched fatty acids

Double bond migration to methylidene positions during electron ionization mass spectrometry of branched monounsaturated fatty acid derivatives

Electron ionization mass spectra of several monounsaturated methyl-branched fatty acid methyl and trimethylsilyl esters were examined. These spectra exhibited some intensive fragment ions, whose formation could be explained after double-bond migration to methylidene position. This preferential migration (substantiated by deuterium labeling) acts significantly in the case of monounsaturated fatty acid methyl and trimethylsilyl esters possessing a methyl branch localized between the penultimate and the C(4) positions (relative to the ester group), whatever the position of the double-bond. Allylic cleavage and gamma-hydrogen rearrangement of the ionized methylidene group thus formed afforded very interesting fragment ions, which could be particularly useful to determine branching positions of monounsaturated methyl-branched fatty acid methyl and trimethylsilyl esters without additional treatment.

Branched chain fatty acids are constituents of the normal healthy newborn gastrointestinal tract

Vernix suspended in amniotic fluid is normally swallowed by the late term fetus. We hypothesized that branched chain fatty acids (BCFA), long known to be major vernix components, would be found in meconium and that the profiles would differ systematically. Vernix and meconium were collected from term newborns and analyzed. BCFA-containing lipids constituted about 12% of vernix dry weight, and were predominantly saturated, and had 11-26 carbons per BCFA. In contrast, meconium BCFA had 16-26 carbons, and were about 1% of dry weight. Meconium BCFA were mostly in the iso-configuration, whereas vernix BCFA contained dimethyl and middle chain branching, and five anteiso-BCFA. The mass of BCFA entering the fetal gut as swallowed vernix particles is estimated to be 180 mg in the last month of gestation whereas the total mass of BCFA found in meconium is estimated to be 16 mg, thus most BCFA disappear from the fetal gut. The BCFA profiles of vernix and meconium show that BCFA are major components of normal healthy term newborn gastrointestinal tract. BCFA are candidates for agents that play a role in gut colonization and should be considered a nutritional component for the fetus/newborn.

Separation among species of Mycobacterium terrae complex by lipid analyses: comparison with biochemical tests and 16S rRNA sequencing

Fatty acids, alcohols, and mycolic acid cleavage products were determined for 13 ATCC strains and 24 clinical isolates, which were initially identified by biochemical and growth characteristics as the Mycobacterium terrae complex. The clinical isolates were also analyzed by partial sequencing of the 16S rRNA gene, which divided them into five genetic entities, M. triviale (three strains), M. terrae (four strains), M. nonchromogenicum sensu stricto (seven strains), Mycobacterium sp. strain MCRO 6 (seven strains), and Mycobacterium sp. strain 31958 (one strain). After acidic methanolysis, secondary alcohols were a characteristic feature in all members of the M. terrae complex but M. triviale. In addition to the prominent secondary alcohols, 2-octadecanol and 2-eicosanol, two previously unidentified alcohols, 2-(8,15-dimethyl)docosenol and 2-(8,17-dimethyl)tetracosenol, were detected in M. nonchromogenicum, Mycobacterium sp. strain MCRO 6, and Mycobacterium sp. strain 31958. Only 2-(8,17-dimethyl)tetracosenol was detected in trace amounts in M. terrae. Genetic differences were associated with differences in phenotypic characteristics, including growth at 42 degrees C and pyrazinamidase production. Based on fatty acid and alcohol composition and biochemical and genetic characteristics, M. non-chromogenicum and Mycobacterium sp. strains MCRO 6 and 31958 were found to be a closely related group, named the M. nonchromogenicum complex. Detected genetic variations associated with phenotypic characteristics may indicate further species separation of this complex. In conclusion, the results of gas-liquid chromatography fatty acid analysis, combined with those of a Tween 80 test, enable identification of the species of the M. terrae complex and their separation from other nonpigmented slowly growing mycobacteria.