Pifithrin-mu, 50 mg

A small molecule p53 inhibitor from STEMCELL Technologies, this compound prevents p53 binding to Bcl-xL and Bcl-2 at the mitochondrial surface without affecting p53 transactivational activities. In vitro, it binds both p53 (Kd = 0.82 mM) and Bcl-xL (Kd = 0.80 mM) and also interacts selectively with heat shock protein 70 (HSP70), disrupting the association between HSP70 and many of its co-chaperones and substrate proteins.

Chemically known as 2-phenylethynesulfonamide, it has a molecular formula of C₈H₇NO₂S, a molecular weight of 181.2 g/mol, and a reported purity of ≥ 98%. The product is supplied as a crystalline solid and is soluble in absolute ethanol and DMSO at concentrations of ≤ 75 mM, though it has low solubility in aqueous media. It is stable at -20°C as supplied and should be protected from prolonged exposure to light.

Published applications include improving cell recovery after cryopreservation when used in combination with the Rho-associated coiled-coil containing protein kinase (ROCK) inhibitor Y-27632, and inhibiting DNA damage-induced apoptosis in human embryonic stem cells. For cell culture use, the stock solution should be diluted into culture medium immediately before use, and final DMSO concentration should be kept at or below 0.1% to avoid potential cell toxicity.