FIASH Reagent

Molecular weight: 664.49. Excitation (nm): 498. Emission (nm): 517. Absorbance (nm): 487. Extinction coefficient (cm-1 M-1): 80000. Quantum yield: 0.7900 (measured with EtOH (neutral))/ 0.95 (measured with 0.1N NaOH). FLASH is a fluorescein derivative, modified to contain two arsenic atoms at a set distance from each other. It was developed by Roger Tsien and colleagues in 1998. The biarsenical labeling technology works through the high-affinity interaction of arsenic for thiols. When FlASH binds to tetracysteine (TC) sequences, its biarsenical group reacts rapidly with Cys-Cys moiety and the tag becomes highly fluorescent in green. The biarsenical labeling reagent FLASH is the smallest expression tag for labeling a protein that contains a six-amino acid motif with a Cys-Cys-X1-X2-Cys-Cys amino acid sequence. The most commonly used tetracysteine is the six amino acid Cys-Cys-Pro-Gly-Cys-Cys sequence. As this sequence rarely appears in endogenous proteins, incorporating the sequence into target proteins generates a small but highly specific target for protein labeling. FLASH generates a strong green fluorescent signal when binding to recombinant proteins containing the tetracysteine motif Cys-Cys-Pro-Gly-Cys-Cys. It can be used for monitoring protein localization, turnover and trafficking, receptor signaling and