Quantification of polyphosphoinositides using selected ion monitoring electrospray mass spectrometry

Polyphosphoinositides (PIP) and (PIP2) show prominent negative singly and doubly charged deprotonated molecules in electrospray mass spectrometry. These ions can be used for quantification of PIP and PIP2 in the low picomole range, without prior chromatographic separation, using selected ion monitoring and consecutive measurements of the signals from the deprotonated singly charged molecules. The dose response curves for both compounds are linear. In a complex matrix consisting of polar lipids (Folch extract) PIP and PIP2 monitored at m/z 965.4 and 1045.5 (stearoyl and arachidonoyl) were determined in the low picomole range, at a flow rate of 100 mu L/min, Collision-induced decomposition of PIP and PIP2 using a mixture of xenon and argon at 25 eV afforded identical high mass ions formed by loss of a molecule of water from PIP and a phosphate group and a molecule of water from PIP2. The results indicate that polyphosphoinositides, and biologically relevant changes in their concentrations, can be quantified directly in cells and cellular membranes by selected-ion monitoring with electrospray mass spectrometry

Mass spectrometric determination of selected microbial constituents using fused silica and chiral glass capillary gas chromatography

Applications of quantitative gas chromatography/mass spectrometry (selected ion monitoring) to clinical and ecological microbiology are described. The technique permits determination of selected microbial metabolites and can be used for the rapid diagnosis of, for example, tuberculosis by ion-focusing of specific branch-chain fatty acids. The technique is also used to determine diaminopimelic and muramic acids, and D- and L-amino acids separated by chiral gas chromatography, in the low picogram range. The latter method has the potential to detect and quantitate microbial populations

Mycelial uptake, translocation and assimilation of N-15-labeled nitrogen by ectomycorrhizal Pinus sylvestris plants

Mycolial uptake, translocation and assimilation of 15N-labelled ammonium was followed in Pinus sylvestris plants infected with the ectomycorrhizal fungus. Paxillus involutus. The distribution of labelled compounds within the systems was examined using gas chromatography / mass spectrometry. Labelled nitrogen was incorporated into a range of free amino acids in the fungal mycelium, the principal sinks being alanine and glutamatelglutamine. Levels of 15 N enrichment declined throughout the transport pathway from 30-45% in the mycelium a~d mycorrhlzal root lips to 3-11% in the plant shoots. A significant proportion of the total assimilated nitrogen (27%) was incorporated into proteinaceous material and the proportion of label present in this fraction increased from 27% in the mycelium to 32% and 58% in the plant roots and needles respectively. The protein-incorporated amino acids showed a wider spectrum of labelling with significant amounts of 15N incorporated into valine, isoleucine, phenylalanine and lysine