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.
Larramendy ML, et al. (1998). Comparison of fluorescein isothiocyanate- and Texas red-conjugated nucleotides for direct labeling in comparative genomic hybridization. Cytometry 31, 174-9; Schneider H (1989). Differential intracellular staining of identified neurons in Locusta with Texas Red and Lucifer Yellow. J Neurosci Methods 30, 107-15.