The NDUFA9 antibody is a crucial tool in studying mitochondrial complex I (NADH:ubiquinone oxidoreductase), a key component of the electron transport chain. NDUFA9 is a nuclear-encoded subunit of complex I, located in the mitochondrial inner membrane. This 39 kDa protein plays a structural role in maintaining complex I stability and is classified as an accessory subunit, distinct from core subunits directly involved in catalytic activity. Antibodies against NDUFA9 are widely used to investigate complex I assembly, expression levels, and mitochondrial dysfunction. Researchers employ these antibodies in techniques like Western blotting, immunofluorescence, and immunohistochemistry to assess protein localization and abundance in disease models. NDUFA9 deficiencies have been linked to mitochondrial disorders such as Leigh syndrome, neurodegenerative diseases, and cancer, where altered complex I function contributes to metabolic reprogramming. The antibody also aids in studying cellular responses to oxidative stress and pharmacological inhibitors targeting mitochondrial respiration. Its specificity makes it valuable for distinguishing complex I defects from other respiratory chain impairments. Studies using NDUFA9 antibodies have advanced our understanding of mitochondrial biology, aging-related pathologies, and therapeutic interventions targeting energy metabolism.