SAMSA-fluorescein

SAMSA-fluorescein, 5- [2(and 3)-5-(acetylmercapto)-succinoyl]amino fluorescein, is a fluorescent probe containing a protected sulfhydryl group. In its protected state, the compound is unre-active. The acetyl-protecting group can be removed by treatment with dilute NaOH at pH 10.0 (Figure 9.9). The resulting free sulfhydryl derivative can be used to label thiol-reactive crosslinkers or to couple with sulfhydryl residues on proteins and other molecules. After activating... 

Figure 9.9 SAMSA-fluorescein contains a protect thiol that can be deblocked by treatment with hydroxy-lamine. The reagent then can be used to modify molecules containing sulfhydryl-reactive groups.

SAMSA-fluorescein is an orange solid compound. Dissolved in buffer at pH 9.0, its maximal wavelength of absorption or excitation is at 495 nm, while its emission wavelength maximum is 520 nm. The reagent and all solutions and derivatives made from it are light sensitive and should be stored in the dark. SAMSA-fluorescein is soluble in aqueous solutions above pH 6.0, but it can be dissolved in DMF to prepare a concentrated stock solution prior to adding a small amount to a buffered reaction mixture. 

To deprotect the acetylated sulfhydryl, dissolve the desired amount of SAMSA-fluorescein (Invitrogen) in lOOmM NaOH, pH 10.0, at a concentration of lOmg/ml. 

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