good probes for specifically labeling HNE modified proteins [43]. Furthermore, the use of click chemistry, orHuisgen 1,3-dipolar cycloaddition, to conjugate an azido-biotin molecule to the alkynyl electrophile tag improves the specificity of isolated protein adducts by enriching themfor alkyne-containing products [45]. Proteomic analysis of affinity-purified biotin-conjugated proteins using alkynylated-HNE probes identified a broad spectrum of electrophile protein targets in an unbiased fashion
[43]. Groups of proteins involved in stress signaling and redox regulation were identified as targets of HNE, emphasizing specific pathways which should be further characterized with respect to their activity following electrophile modification. The combination of internal electrophile probes with affinity purification was the first major step toward achieving a global understanding of the proteins modified by lipid electrophiles during oxidative stress.