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Lipidomics by MPPI-TOFMS using direct analysis

IP.com Disclosure Number: IPCOM000228541D
Publication Date: 2013-Jun-17
Document File: 9 page(s) / 8M

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Abstract

Progress in the emerging field of lipidomics, defined as "the systems-level analysis of lipids and factors that interact with lipids" (Wenk, Nature 2005, vol 4, p594) has been hampered by many factors including inadequate protocols for sample preparation, lack of an integrated platform to comprehensively measure all lipid components of a tissue or cell in one experiment, virtual absence of a reference database, and the fact that lipids are even difficult to define (see Wenk, supra). According to a more recent review paper by Li et al. (Anal. Bioanal. Chem. 2011, 399, 243) lipids are divided into eight categories: fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterol lipids, saccharolipids, and polyketides. Analytical tools used in either of the three analytical approaches in lipidomics (i.e., untargeted-, focused-, or targeted lipidomics) include mass spectrometry with a variety of ionization technologies (i.e., electrospray ionization (ESI), desorption electrospray ionization (DESI), laser ablation electrospray ionization (LAESI), laser desorption ionization (LDI), matrix assisted laser desorption ionization (MALDI), nuclear magnetic resonance (NMR) and 2 dimensional nuclear magnetic resonance (2D-NMR), ion mobility spectrometry (IMS), and other spectroscopic techniques such as infra red (IR). The most common analytical tool seems to be direct infusion mass spectrometry with ESI and MALDI, however, without any separation technique, ion suppression effects are quite serious in ESI and limit the application of this technology when used in lipid profiling. Despite these disadvantages, the mass spectrometric analysis of lipids is presently done using two complementary approaches: direct infusion (i.e., "shotgun lipidomics") using ESI-MS and high performance liquid chromatography (HPLC)-ESI-MS (see Metabolic Profiling, Methods in Molecular Biology 708, 2011, Ch. 16).

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Lipidomics by MPPI-TOFMS using direct analysis

Viorica Lopez-Avila
Agilent Technologies, Inc.

Progress in the emerging field of lipidomics, defined as “the systems-level analysis of lipids and factors that interact with lipids” (Wenk, Nature 2005, vol 4, p594) has been hampered by many factors including inadequate protocols for sample preparation, lack of an integrated platform to comprehensively measure all lipid components of a tissue or cell in one experiment, virtual absence of a reference database, and the fact that lipids are even difficult to define (see Wenk, supra).  According to a more recent review paper by Li et al. (Anal. Bioanal. Chem. 2011, 399, 243) lipids are divided into eight categories: fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterol lipids, saccharolipids, and polyketides.  Analytical tools used in either of the three analytical approaches in lipidomics (i.e., untargeted-, focused-, or targeted lipidomics) include mass spectrometry with a variety of ionization technologies (i.e., electrospray ionization (ESI), desorption electrospray ionization (DESI), laser ablation electrospray ionization (LAESI), laser desorption ionization (LDI), matrix assisted laser desorption ionization (MALDI), nuclear magnetic resonance (NMR) and 2 dimensional nuclear magnetic resonance (2D-NMR), ion mobility spectrometry (IMS), and other spectroscopic techniques such as infra red (IR).  The most common analytical tool seems to be direct infusion mass spectrometry with ESI and MALDI, however, without any separation technique, ion suppression effects are quite serious in ESI and limit the application of this technology when used in lipid profiling.  Despite these disadvantages, the mass spectrometric analysis of lipids is presently done using two complementary approaches: direct infusion (i.e., “shotgun lipidomics”) using ESI-MS and high performance liquid chromatography (HPLC)-ESI-MS (see Metabolic Profiling, Methods in Molecular Biology 708, 2011, Ch. 16).

The lipid analysis method described herein uses antibodies to capture specific classes of lipids from a biological sample, followed by release of the lipids from the antigen-antibody complex. Standard protocols in immunoaffinity chromatography (see, e.g., Harlow and Lane Using Antibodies: A Laboratory Manual 1999 CSHL Press) may be used to capture the lipids, and the subsequent analysis may be done by direct MPPI- time-of-flight mass spectrometry (TOFMS) or quadrupole time-of-flight mass spectrometry (QTOFMS).  Direct analysis of steroids by direct injection microplasma photoionization- (MPPI) TOFMS, has already been demonstrated (see figure below: Fig. 1 shows the electron ionization (EI) mass spectra for various steroids; Fig. 2 shows the Kr MPPI mass spectra for various steroids analyzed by direct injection.; Fig. 3 shows the Kr MPPI mass spectra for various cholesterols analyzed by direct injection; Fig. 4 shows the Kr MPPI spectrum for a mixture of 8 s...