Fluorescein 5-isothiocyanate → 2-(6-Hydroxy-3-oxo-3H-xanthen-9-yl)benzoic acid

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Reaction Steps

This HA-HZ was dissolved in distilled water (Milli Q water), and an equal amount of 100 mM carbonate buffer (Ph 9.0) was then added thereto to a final concentration of 1 mg/ml. Thereafter, FITC dissolved in DMSO that was 1/10 the volume of the HA-HZ solution was added to the mixture at an additive ratio of FITC/HA unit=3.0 mol/mol, and the obtained mixture was then reacted in the dark at room temperature for 1 hour. Thereafter, 25 ml of the reaction solution was poured in PD-10 columns (10 columns) that had previously been equilibrated with a 50 mM carbonate buffer (pH 9.0), so as to remove unreacted FITC. Succinic anhydride dissolved in DMSO (3.5 ml) was added to the thus roughly purified solution at an additive ratio of succinic anhydride/HZ=250 mol/mol, and the same above reaction was carried out. The reaction mixture was dialyzed against large excess amount of distilled water (Milli Q water) for purification, followed by freeze-drying, so as to obtain fluorescein-labeled HA-HZ-SUC, which was formed by labeling HA-HZ with FITC.

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