Abstract
A method of direct lipid analysis by MALDI mass spectrometry in intact membranes, without prior extraction/separation steps, is described. The purple membrane isolated from the extremely halophilic archaeon Halobacterium salinarum was selected as model membrane. Lyophilized purple membrane were grinded with 9-aminoacridine (9-AA) as dry matrix, and the powder mixture was crushed in a mechanical die press to form a thin pellet. Small pieces of the pellet were then attached to the MALDI target and directly analyzed. In parallel, individual archaebacterial phospholipids and glycolipids, together with the total lipid extract of the purple membrane, were analyzed by MALDI-TOF/MS using 9-AA as the matrix in solution. Results show that 9-AA represents a suitable matrix for the conventional MALDI-TOF/MS analysis of lipid extracts from archaeal microorganisms, as well as for fast and reliable direct dry lipid analysis of lyophilized archaebacterial membranes. This method might be of general application, offering the advantage of quickly gaining information about lipid components without disrupting or altering the membrane matrix.
Highlights
A method of direct lipid analysis by MALDI mass spectrometry in intact membranes, without prior extraction/separation steps, is described
The names of individual lipid components in the total lipid extract of purple membrane (PM) are reported on the side of TLC plate in Fig. 3A, together with the monoisotopic molecular masses obtained by MALDI-TOF/matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MS) analysis
It has been shown that MALDI mass spectrometry allows the analysis of glycerolipids, glycerophospholipids, triglycerides, cholesterol, and cholesterol derivatives, while reports describing the application of MALDI to the analysis of archaebacterial lipids are not yet available
Summary
A method of direct lipid analysis by MALDI mass spectrometry in intact membranes, without prior extraction/separation steps, is described. As many of the lipid components of archaeal cell membranes are not commercially available, we have isolated and purified individual archaeal lipids for MALDI-TOF/ MS analysis. The simplified method of sample preparation for MALDI lipid analysis is suitable for other archaebacterial membranes in lyophilized form.
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