Sulforhodamine 101 is a red fluorescent dye. It is used for cell imaging methods, and was shown to label astrocytes, myelinating oligodendrocytes.SR101 has been reported to affect excitability of neurons and should therefore be used with caution.
Sulforhodamine 101 acid chloride is quite unstable in water, especially at the higher pH required for reaction with aliphatic amines. Protein modification by this reagent is frequently done at low temperature. This reagent reacts with amine compounds such as amino acids, peptides and proteins to give bright red fluorescent conjugates that are extremely stable, and resistant to protease-catalyzed hydrolysis.