P-252 - Study of covalent adduction of nitrated phospholipids to peptides using tandem mass spectrometry in different instruments.

Lipids are targets of reactive nitrogen species (RNS). Nitro-fatty acids (NO2-FA) are well-known products of RNS and have been associated with anti-inflammatory and cytoprotective effects. NO2-FAs play their biological actions mainly by covalent adduction to key peptides/proteins, modulating their roles. Nitroxidation of phospholipids (PL) has been recently detected in biological samples, but their biological effects were not addressed. We hypothesize that nitrated PL may react with peptide/proteins. We performed in vitro biomimetic assays to synthetize adducts of nitrated POPC (NO2-POPC), already detected in biological samples, and GSH. The formation of NO2-POPC-GSH adducts was studied by ESI-MS and MS2, and low and high energy CID using different MS platforms. Typical product ions observed under MS2 conditions are b, y and immonium ions bearing NO2-POPC covalently-linked that unequivocally confirmed the presence of the lipid-peptide adduct. In summary, the characterization of nitro PL-peptide adducts by MS and MS2 allowed the identification of specific reporter ions to be used to pinpoint these adductions in biological systems. [ABSTRACT FROM AUTHOR]