Anti-IRS1 (phospho S639) Antibody

Raised in rabbit against a synthetic phosphopeptide spanning the Ser639 region of human IRS-1, this unconjugated polyclonal IgG selectively binds the insulin receptor substrate 1 protein only when that residue is phosphorylated. Phosphorylation at Ser639 is driven by the mTOR/S6K1 axis and serves as a readout of nutrient-sensing and insulin signaling activity, which is why the reagent is widely used to monitor insulin resistance, growth factor response, and metabolic pathway activation in cell lysates and fixed tissue sections.

The 50 µl liquid aliquot is supplied in phosphate-buffered saline containing 150 mM NaCl, 50% glycerol, and 0.02% sodium azide and is affinity-purified against the epitope-specific phosphopeptide, with non-phospho-specific antibodies removed by negative-affinity chromatography. Validation data from Antibodies.com supports western blot and immunohistochemistry workflows on human, mouse, and rat samples, where the antibody produces cytoplasmic staining in tissues displaying elevated S6K1 activity. For western blot, dilute 1:500 to 1:2000 in 5% BSA/TBS-T and incubate overnight at 4 °C; for IHC, antigen retrieval with citrate buffer (pH 6.0) followed by standard HRP-based detection is recommended.

Upon arrival, aliquot the reagent and keep it frozen at -20 °C to preserve phospho-specific binding, avoiding repeated freeze-thaw cycles. Brief refrigeration at 4 °C is acceptable for short-term use, and the vial should be protected from light. The reagent is intended for research use only.