Oxidative stress, biomarkers aldehydes

Amino acid residues are potential targets of free radical oxidation and nitration. Carbonyl derivatives of proteins may be formed by the interaction of protein amino acid side chains, mainly cysteine, histidine, and lysine residues with reactive aldehydes, such as HNE and ONE generated by peroxidation of PUFAs (polyunsaturated fatty acids). Amino acid and peptide biomarkers of oxidative stress are typically focused on specific proteins related to disease pathology. For instance, the oxidation of histidine and methionine are typically discussed in (3-amyloid plaque formation and HNE-derived histidine adducts are the main focus of modifications on low-density lipoprotein (LDL) (An-nangudi et al., 2008). However, there are several specific examples of general biomarkers of oxidative stress that include endogenous histidine containing dipeptides such as carnosine and anserine as well as the very stable o,o -dityrosine. These will be discussed below. 

Example 4-Hydroxynon-2-enal (4-HNE) is a major aldehydic product of lipid peroxidation (LPO), its products being indicators for oxidative stress. In order to introduce LPO products as biomarkers, a GC-MS method for 4-HNE detection in clinical studies [35] was developed using a sample volume of 50 pi of plasma. For improved GC separation and subsequent mass spectral detection the aldehyde is converted into the pentafluorobenzyl-hydroxylimine and the hydroxy group is tri-methylsilylated [36]. The TIC acquired in electron capture mode (EC, Chap. 7.4) exhibits 50 chromatographic peaks (Fig. 14.2). Those related to the target compounds can easily be identified from suitable RICs. The choice of potentially useful m/z values for RICs is made from the EC mass spectrum of the pure 4-HNE derivative (below). In this case, [M-HF], m/z 403, [M-HOSiMes] , m/z 333, and [CeFs]", m/z 167, are indicative, while [CH2C6F5] , m/z 181, is not. 

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