A researcher measures a potent nitrating species formed when nitric oxide reacts rapidly with superoxide anion. This reaction product, responsible for tyrosine nitration of proteins in inflammatory and neurodegenerative states, is:

• A Nitrite (NO2−)
• B S-nitrosoglutathione
• C Hypochlorous acid (HOCl)
• D Peroxynitrite (ONOO−) ✓

Explanation

Nitric oxide combines with superoxide at a near diffusion-limited rate to form peroxynitrite, a reactive nitrogen species that nitrates protein tyrosine residues (nitrotyrosine) and damages DNA and lipids. Hypochlorous acid is produced by myeloperoxidase from hydrogen peroxide and chloride, not from nitric oxide, making it the best distractor. Peroxynitrite is implicated in atherosclerosis, stroke and neurodegeneration.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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