LC-MSN METHOD FOR QUALITATIVE & QUANTITATIVE ANALYSIS OF COMPLEX LIPID MIXTURES

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. While nanospray MS is a good choice for the characterization of simple lipid mixtures (1,2), it is often not sufficient for the qualitative and quantitative analysis of highly complex samples. Most separation methods described are limited, in that they either target only specific classes of interest (3), or are not well suited for MS, the superior detection method, especially for analyses of small amounts of samples. We previously developed a simple, reproducible three-step method for lipid analysis by adapting separation systems described in the literature for the chromatography of lipids (4,5,6). After an optional initial fractionation, normal phase HPLC-MS first provided class separation and then a reversed phase LC-MS/MS system answered remaining questions. Isolated and extracted LDL lipids and lipid standards were separated by 1D or 2D LC and detected by mass spectrometry in positive and negative ion modes. Two different gradients were used for the separation of more nonpolar and more polar lipids. Quantification was based on this step. We are now simplifying this method using UPLC. Fractions are characterized by LC-MS/MS using athe QStar QoTOF MS, or LTQ-Orbitrap MS, or by nanospray MS/MS and/or precursor ion scanning. Lipid and glycolipid standards containing diverse nonpolar, phospho- and glycolipids have been reproducibly separated on the basis of polarity. This step, when used for biological samples, also serves to protect the following column, but is not always necessary. The accuracy of the quantification depends mostly on the quality of internal and external standards available. The system is being applied to the analysis of lipids associated with prions and to sulfatide fractions from human milk that show anti-HIV acrivity. 1) M. Puffer and R.C. Murphy (2003). Mass Spectrometry Reviews 22, 332-64. 2) X. Han and R.W. Gross (2005). Mass Spectrom Rev. 24, 367-412. 3) R.C. Murphy et al. (2001). Chem. Rev. 101, 479-526. 4) J. Hamilton, and K. Comai (1988). Lipids 23, 1046-49 & 1150-53. 5) W.W. Christie et al. (1995). J. High Resol. Chromatogr. 18, 97-100. 6) F.K. Welty et al. (1991). J. Clin. Invest. 87, 1748-1754. 7) U. Sommer et al. (2006) J. Lipid Res. 47, 804-814.