4-bromo A23187 is a halogenated analog of the highly selective calcium ionophore A23187. 4-bromo A23187 is non-fluorescent.[1] As a result, it is often used in experiments where fluorescent probes are employed.[2],[3]
Reference:
[1]. Deber, C.M., Tom-Kun, J., Mack, E., et al. Bromo-A23187: A nonfluorescent calcium ionophore for use with fluorescent probes. Anal.Biochem. 146(2), 349-352 (1985).
[2]. Ducreux, S., Gregory, P., and Schwaller, B. Inverse regulation of the cytosolic Ca2+ buffer parvalbumin and mitochondrial volume in muscle cells via SIRT1/PGC-1α axis. PLoS One 7(9), (2012).
[3]. Yang, J., Singh, V., Cha, B., et al. NHERF2 protein mobility rate is determined by a unique C-terminal domain that is also necessary for its regulation of NHE3 protein in OK cells. J.Biol.Chem. 288(23), 16960-16974 (2013).