Biotin-4-fluorescein has been reported to be a superior fluorescent biotin derivative for accurate measurement of avidin and streptavidin in crude biofluids. The biotin binding to avidin and streptavidin is high affinity, fast and noncooperative. Also see Fluorescein biotin (80019 ). Please also see biotin-rhodamine 110 (80022 ) for superior photostability.

• l_ex\l_em = 494/523 nm. 
• Yellow solid soluble in DMSO, or pH>7 buffers.
• Store at -20°C and protect from light. 
• C₃₃H₃₂N₄O₈S.
• Mwt. = 644.7