A ready-to-use buffer useful for lysing cells and tissues for radioimmunoprecipitation assay. RIPA buffer also results in low background in immunoprecipitation/pull down assays. The buffer (1X) contains 150 mM NaCl, 1% IGEPAL® CA-630, 0.5% of Sodium Deoxycholate, 0.1% sodium dodecylsulfate (SDS), and 50 mM Tris.