Anal Chem. 2007 Jun 1;79(11):4083-93. Epub 2007 May 3. Top-down lipidomic screens by multivariate analysis of high-resolution survey mass spectra. Schwudke D1, Hannich JT, Surendranath V, Grimard V, Moehring T, Burton L, Kurzchalia T, Shevchenko A. Abstract

Direct profiling of total lipid extracts on a hybrid LTQ Orbitrap mass spectrometer by high-resolution survey spectra clusters species of 11 major lipid classes into 7 groups, which are distinguished by their sum compositions and could be identified by accurately determined masses. Rapid acquisition of survey spectra was employed as a "top-down" screening tool that, together with the computational method of principal component analysis, revealed pronounced perturbations in the abundance of lipid precursors within the entire series of experiments. Altered lipid precursors were subsequently identified either by accurately determined masses or by in-depth MS/MS characterization that was performed on the same instrument. Hence, the sensitivity, throughput and robustness of lipidomics screens were improved without compromising the accuracy and specificity of molecular species identification. The top-down lipidomics strategy lends itself for high-throughput screens complementing ongoing functional genomics efforts.

Mass Spectrometric Analysis. Analyses were performed on a  LTQ  Orbitrap  hybrid  mass  spectrometer  (Thermo  Fisher Scientific, Bremen, Germany) equipped with a robotic nanoflow ion source NanoMate HD (Advion BioSciences Ltd., Ithaca, NJ) with 4.1-ím nozzle diameter chip or, where specified, on a static nano  ESI  or  ESI  ion  sources  (both  from  Thermo  Fischer Scientific). NanoMate HD was controlled by Chipsoft 6.4. software (Advion Biosciences) and operated at the ionization voltage of 1.05 kV and gas pressure 1 psi. When using the nano ESI source, the spraying voltage was adjusted individually within the range of 1.1 -1.4 kV. Metal-coated glass needles were from Proxeon Biosystems (Odense M, Denmark) or MasCom Analysengera¨te Service GmbH (Bremen, Germany). When using an ESI source, samples were infused at the flow rate of 5 íL/min delivered by a built-in syringe pump and the spraying voltage of 3.8 kV was applied.