Dihydroxybenzoic lipid analysis

Cvacka, J. and Svatos, A. (2003) Matrix-assisted laser desorption/ ionization analysis of lipids and high molecular weight hydrocarbons with lithium 2,5-dihydroxybenzoate matrix. Rapid Commun. Mass Spectrom., 17,... 

As a practical example, when a mouse brain section to which 2,5-dihydroxybenzoic acid (DHB) has been applied as a matrix is subjected directly to MS in positive ion-detection conditions, strong peaks which are mainly derived from phospholipids were observed in mass region of 700 < m/z < 900 [8] on the other hand, signals derived from proteins, meanwhile, are scarcely detected at m/z > 3000 [9].This is because phospholipids ionize much more efficiently than proteins, and they, on the other hand, suppress protein/peptide ionization. Therefore, for detecting/imaging proteins and peptides, removal of such lipids improves the sensitivity for proteins analysis. To this end, tissue sections should be rinsed with organic solvent, to remove lipids from tissue samples [9-11]. 

Selection of a suitable matrix to analyze a particular lipid class or a category of lipid classes is important for MALDI-MS analysis of lipids and has been well documented [54-57], It is conventional to use a-cyano-4-hydroxycinnamic acid (CHCA) for analysis of lipids in the positive-ion mode while 2,5-dihydroxybenzoic acid (DHB) in the negative-ion mode. Utilization of these matrices results in some of the obstacles for quantitative and global analyses of cellular lipidomes (see Chapter 2). 

MALDI matrix is typically a small organic acid that co-crystallizes with analytes extracted from the tissne section to allow absorption of energy of the pulsed laser. Matrix and analytes are ablated and ionized from the tissne snrfece with subsequent MS analysis. Common matrixes used for the analysis of peptides, lipids, and small drng molecules are 2,5-dihydroxybenzoic acid (DHB) and a-cyano-4-hydroxycinnamic acid (CHCA) while sinapinic acid (S A) is most often used for protein analysis. 1.23,26,27) An organic solvent snch as acetonitrile or methanol can be used for extraction of small molecules from tissne sections prior to matrix co-crystallization. ... 

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