Abstract
Phospholipids and triacylglycerols (TAGs) are important classes of lipids in biological systems. Rapid methods have been developed for their characterization in crude samples, including MALDI time-of-flight MS. For mixtures, MALDI often selectively shows only some components. For example, phosphatidylcholine (PC) suppresses detection of other lipids. Most rapid MS methods detect either TAGs or phospholipids but not both. Herein, we demonstrate a simple approach to rapidly screen mixtures containing multiple lipid classes. To validate this approach, reference lipids [PC, tripalmitin (PPP), and phosphatidyl-ethanolamine (PE)] and real samples (beef, egg yolk) were used. In a binary mixture with a strong suppressor (PC), PPP was greatly suppressed. After a simple separation, suppression was virtually eliminated. A mixture of nominally nonsuppressing lipids (PE and PPP) was not adversely affected by separation. Ground beef and egg yolk were used to demonstrate detection of known lipid compositions where other methods have missed one or more lipids or lipid classes. Separation was performed using solid phase extraction with a PrepSep florisil column. A 10 min separation allows rapid screening for lipids and changes in lipids. It is sufficient to clearly detect all lipids and overcome suppression effects in complex lipid mixtures.
Highlights
Phospholipids and triacylglycerols (TAGs) are important classes of lipids in biological systems
This rapid MALDI-MS approach cannot currently be applied to experiments requiring the detection of multiple lipid classes in an unresolved mixture
The approach we report is the application of simple solid phase extraction (SPE) cartridges to produce a few fractions from which lipids and classes of lipids can be characterized by rapid and direct MALDI-MS analysis
Summary
Phospholipids and triacylglycerols (TAGs) are important classes of lipids in biological systems. Examples of applications where it is important to detect multiple lipid classes [i.e., phospholipids and triacylglycerols (TAGs)] include food analysis [1,2,3], cell biology [4], health effects [5], taxonomy [6], and other fields [7,8,9,10,11]. Gidden et al [16] have reported using MALDI-MS to rapidly differentiate Escherichia coli and Bacillus subtilis based on the phospholipid profile and monitor changes in lipid content during the growth phases of the bacteria This rapid MALDI-MS approach cannot currently be applied to experiments requiring the detection of multiple lipid classes in an unresolved mixture. MALDI-MS of brain lipid extracts, using a silica gel cation exchanger for separation of components, have been reported for the detection of phospholipids, but the detection of TAGs was again not reported [19]
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