Tryptophan with peroxidizing lipid

Peroxynitrite is a nonspecific oxidant that reacts with all classes of biomolecules depleting low-molecular-weight antioxidants, initiating lipid peroxidation, damaging nucleic acids and proteins. Its reactions are much slower than those of the hydroxyl radical but are faster than those of hydrogen peroxide. Comparison of peroxynitrite reactivity with various amino acid residues of human serum albumin have shown that cysteine, methionine, and tryptophan are the most reactive... 

In biological systems, free radicals can react with cellular macromolecules in a variety of ways, the most important of which is hydrogen abstraction from DNA leading to chain scission or cross-linking. In proteins, tryptophan is the amino acid residue most susceptible to free radical attack. Lipid peroxidation by free radicals in turn is liable to cause alteration in cell membranes. 

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