Sulforhodamine B sodium salt

Sulforhodamine B (SRB) is a water-soluble, anionic red fluorescent aminoxanthene dye. It is often used as a membrane-impermeable polar tracer or for cell density determination via determination of cellular proteins (cytotoxicity assay). The SRB assay is extensively used for in vitro cytotoxicity screening and in cell based studies. This method relies on the property of SRB, which binds stoichiometrically to proteins under mild acidic conditions and then can be extracted using basic conditions. Thus, the amount of bound dye can be used as a proxy for cell mass, which can then be extrapolated to measure cell proliferation. Spectral Data: λex 560nm, λem 580nm.