Biomedical subjects

Christer S Ejsing

Publications and source records attributed to Christer S Ejsing.

5 recordsLinked to original sources

PubMed2006

Automated identification and quantification of glycerophospholipid molecular species by multiple precursor ion scanning.

We report a method for the identification and quantification of glycerophospholipid molecular species that is based on the simultaneous automated acquisition and processing of 41 precursor ion spectra, specific for acyl anions of common fatty acids moieties and several lipid class-specific fragment ions. Absolute quantification of identified species was linear within a concentration range of 10 nM-100 microM and was achieved by spiking into total lipid extracts a set of synthetic lipid standards with diheptadecanoyl (17:0/17:0) fatty acid moieties, representing six common classes of glycerophospholipids. The automated analysis of total lipid extracts was powered by a robotic nanoflow ion source and produced currently the most detailed description of the glycerophospholipidome.

Fatty Acids↗

PubMed2006

Lipid profiling by multiple precursor and neutral loss scanning driven by the data-dependent acquisition.

Data-dependent acquisition of MS/MS spectra from lipid precursors enables to emulate the simultaneous acquisition of an unlimited number of precursor and neutral loss scans in a single analysis. This approach takes full advantage of rich fragment patterns in tandem mass spectra of lipids and enables their profiling by complex (Boolean) scans, in which masses of several fragment ions are considered within a single logical framework. No separation of lipids is required, and the accuracy of identification and quantification is not compromised, compared to conventional precursor and neutral loss scanning.

Animals↗

PubMed2006

Collision-induced dissociation pathways of yeast sphingolipids and their molecular profiling in total lipid extracts: a study by quadrupole TOF and linear ion trap-orbitrap mass spectrometry.

The yeast Saccharomyces cerevisiae synthesizes three classes of sphingolipids: inositolphosphoceramides (IPCs), mannosyl-inositolphosphoceramides (MIPCs), and mannosyl-diinositolphosphoceramides (M(IP)2C). Tandem mass spectrometry of their molecular anions on a hybrid quadrupole time-of-flight (QqTOF) instrument produced fragments of inositol-containing head groups, which were specific for each lipid class. MS(n) analysis performed on a hybrid linear ion trap-orbitrap (LTQ Orbitrap) mass spectrometer with better than 3 ppm mass accuracy identified fragment ions specific for the amide-linked fatty acid and the long chain base moieties in individual molecular species. By selecting m/z of class-specific fragment ions for multiple precursor ion scanning, we profiled yeast sphingolipids in total lipid extracts on a QqTOF mass spectrometer. Thus, a combination of QqTOF and LTQ Orbitrap mass spectrometry lends itself to rapid, comprehensive and structure-specific profiling of the molecular composition of sphingolipids and glycerophospholipids in important model organisms, such as fungi and plants.

Glycerophospholipids↗

PubMed2004

Polyene-lipids: a new tool to image lipids.

Microscopy of lipids in living cells is currently hampered by a lack of adequate fluorescent tags. The most frequently used tags, NBD and BODIPY, strongly influence the properties of lipids, yielding analogs with quite different characteristics. Here, we introduce polyene-lipids containing five conjugated double bonds as a new type of lipid tag. Polyene-lipids exhibit a unique structural similarity to natural lipids, which results in minimal effects on the lipid properties. Analyzing membrane phase partitioning, an important biophysical and biological property of lipids, we demonstrated the superiority of polyene-lipids to both NBD- and BODIPY-tagged lipids. Cells readily take up various polyene-lipid precursors and generate the expected end products with no apparent disturbance by the tag. Applying two-photon excitation microscopy, we imaged the distribution of polyene-lipids in living mammalian cells. For the first time, ether lipids, important for the function of the brain, were successfully visualized.

3T3-L1 Cells↗

PubMed2003

Charting molecular composition of phosphatidylcholines by fatty acid scanning and ion trap MS3 fragmentation.

The molecular composition of phosphatidylcholines (PCs) in total lipid extracts was characterized by a combination of multiple precursor ion scanning on a hybrid quadrupole time-of-flight mass spectrometer and MS3 fragmentation on an ion trap mass spectrometer. Precursor ion spectra for 50 acyl anion fragments of fatty acids (fatty acid scanning) acquired in parallel increased the specificity and the dynamic range of the detection of PCs and identified the fatty acid moieties in individual PC species. Subsequent analysis of detected PC peaks by MS3 fragmentation on an ion trap mass spectrometer quantified the relative amount of their positional isomers, thus providing the most detailed and comprehensive characterization of the molecular composition of the pool of PCs at the low-picomole level. The method is vastly simplified, compared with conventional approaches, and does not require preliminary separation of lipid classes or of individual molecular species, enzymatic digestion, or chemical derivatization. The approach was validated by the comparative analysis of the molecular composition of PCs from human red blood cells. In the total lipid extract of Madin-Darby canine kidney II cells, we detected 46 PC species with unique fatty acid composition and demonstrated that the presence of positional isomers almost doubled the total number of individual molecular species.

Animals↗