As described above, one of the major reactions that electrophiles, including HNE, can undergo with protein ucleophiles is Michael addition. Electrophiles are able to form Michael adducts with cysteine thiols, histidine imidazoles and lysine ε-amines on target proteins. MichaeladditionofHNE to targetproteins results in the formation of a residual carbonyl group. Biotin hydrazide reacts with protein carbonyls, including the residual carbonyl moieties formed during Michael addition of HNE to protein nucleophiles, to generate stable hydrazone derivatives