O-Phospho-L-tyrosine is a critical biochemical reagent in phosphorylation research and proteomics. It serves as a standard reference compound for identifying and quantifying phosphotyrosine residues in proteins via LC-MS/MS, ELISA, and Western blotting. In cell signaling studies, it acts as a substrate or competitor to probe tyrosine kinase and phosphatase activities, helping elucidate pathways involved in cell proliferation, differentiation, and malignant transformation. It is also used as a calibrant in two-dimensional electrophoresis and thin-layer chromatography for phosphoamino acid analysis. Additionally, it functions as a key building block for synthesizing phosphotyrosine-containing peptides, which are essential for studying protein-protein interactions mediated by SH2 and PTB domains. Its high purity and stability make it indispensable in academic research, pharmaceutical development, and clinical diagnostics.

GHS Classification: H302 (Harmful if swallowed), H315 (Causes skin irritation), H319 (Causes serious eye irritation), H335 (May cause respiratory irritation). Acute toxicity: Oral LD50 (rat) >500 mg/kg; no data on dermal or inhalation toxicity. Skin contact may cause redness, itching, or mild dermatitis; eye contact can lead to irritation, tearing, or corneal discomfort. Inhalation of dust may irritate the respiratory tract, causing coughing or shortness of breath. No evidence of carcinogenicity, mutagenicity, or reproductive toxicity. Environmental hazard: WGK 3 (Highly harmful to aquatic organisms); avoid release into water or soil. Handle in a ventilated area with nitrile gloves, safety goggles, and an N95 respirator. Store sealed at ?20 °C in a dry place, away from moisture and strong oxidants. Spills should be collected and disposed of as hazardous waste; rinse skin/eyes with plenty of water if contact occurs.